Ch 1 - Atomic Structure Flashcards
The study of Atomic Structure
1
Q
To calculate the atomic mass of a number, what do you need to know?
A
The number of stable isotopes of the element, the mass of each isotope, and the natural percent abundance of each isotope.
2
Q
define the term atomic number of an element?
A
the number of protons in the nucleus of an atom
3
Q
What is an Atom?
A
- Atoms are the smallest particles of an element that have the chemical properties of that element.
- All atoms consist of three particles, called protons, neutrons and electrons.
- Each atom has a nucleus at approximately the centre of its volume consisting of the two types of particles called protons and neutrons.
- The nucleus of an atom is positively charged.
- Electrons are distributed around the volume of the atom of which they are a part in “shells”, “orbits” or “energy levels”
4
Q
In 1913, Niels Bohr suggested an explanation for the emission spectrum by proposing a model for the hydrogen atom. What did he propose?
A
- He proposed that electrons of specific energy move around the central nucleus in circular orbits or energy levels.
- Electrons cannot exist between these orbits
- Although an electron cannot lose energy while orbiting a nucleus, it could be given excess energy (by a flame or electric current) and then move to a higher orbit. If this happens, the electron has moved from the ground state (lowest energy level) to an excited state.
- When it drops back down to a lower, more stable orbit, this excess energy is given out as a photon or quantum of light. This is seen as a line of a particular colour on the visible spectrum.
5
Q
What are 5 Problems with the Bohr Model?
A
- It violates the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit.
- The Bohr Model provides an incorrect value for the ground state orbital angular momentum.
- It makes poor predictions regarding the spectra of larger atoms.
- It does not predict the relative intensities of spectral lines.
- The Bohr Model does not explain fine structure and hyperfine structure in spectral lines.
- It does not explain the Zeeman Effect.
6
Q
List of 5 important facts about Compounds.
A
- Compounds consist of molecules formed from atoms of 2 or more different elements bound together chemically.
- Compounds can be broken down into a simpler type of matter (elements) by chemical means; not by physical means
- Compounds always contains the same ratio of component elements.
- Compounds have properties different from their component elements
- e.g. the compound water (H2O) is a liquid at room temperature and pressure and has different chemical properties from those of the two elements, hydrogen (H2) and oxygen (O2), from which it is formed.
- Compounds can be represented using chemical formulae.
7
Q
- Draw a diagram to show the arrangement of carbon atoms in a diamond crystal.
A
8
Q
Do all covalent bonds conduct electricity?
A
NO (except graphite and graphene)
9
Q
- Diamond, graphite and silicon dioxide are all examples of giant covalent structures. What does the word giant mean in this context?
A
- it continues on and on in three dimensions.
10
Q
- Draw a diagram or diagrams to show the arrangement of carbon atoms in a graphite crystal.
A
11
Q
Give 3 examples of a giant covalent structure
A
- Graphite
- Diamond
- SiO2
12
Q
What is electrical current?
A
The movement of charged particles such as ions or electrons in a circuit.
13
Q
Whose experiments were to find the quantity of charge carried by an electron?
A
Robert A. Millikan started his work on electron charge in 1906 and continued for seven years. His 1913 article announcing the determination of the electron’s charge is a classic and Millikan received the Nobel Prize for his efforts.
14
Q
- What is electron configuration?
A
- The arrangement of electrons in the shells is called the atom’s electron configuration
- The electron capacity of each shell is limited.
- The maximum number of electrons that each shell can hold is 2n2 where n is the shell number or energy level.
- Electron shells are filled in order from the nucleus, starting with the K shell, so that the electrons are in their lowest possible energy levels (or ground state).
15
Q
What are some Key Facts about Electrons?
A
- Electrons exist in the volume of atoms that surrounds the nucleus (see the diagram of an atom, on the right) and not in the nucleus of atoms - which is where the protons and neutrons are located.
- Electrons are therefore subatomic particles but they are not nucleons.
- Electrons have a negative charge of -1.
- An electron has a mass approximately 1/1836 of the mass of a proton, so a relative mass of 1/1836 ≈ 0.0005 ≈ zero. Electrons therefore account for very little of the total mass of the atom of which they are a part.
- The number of electrons in an atom is the same as the number of protons in the atom. That is because atoms are charge neutral, and protons have a charge of +1 while electrons have a charge of -1 so there must be the same number of each in order for the whole atom to be charge neutral. Recall that the number of protons in an atom is the atomic number of that atom (element).
16
Q
How do you know how many electrons are in an element based upon what you see in the periodic table?
A
Check the atomic number, there are equal protons and electrons
17
Q
When was the electron discovered? and
Who discovered the electron?
A
The electron was discovered in 1897 by British physicist J.J. Thomson who was working with Cathode Rays at the Cavendish Laboratory, Cambridge University.
18
Q
Are electrons positively charged or negatively charged?
A
Negatively charged.
19
Q
Elements are different because they contain different numbers of _______.
A
protons
20
Q
Elements of the same period have the same number of
A
Electron shells
21
Q
Elements such as O2 and Br2 are…
A
Diatomic molecules
22
Q
Elements with the same group have the same number of…
A
Electrons in the outer shell
23
Q
List 4 important facts about Chemical Elements.
A
- Elements consist of only one type of atom - which may, or may not be joined together to form molecules or large structures, so …
- Elements can exist either as atoms (e.g. argon) or as molecules (e.g., nitrogen)
- Elements cannot be broken down into a simpler type of matter by either physical or chemical techniques - though some larger elements break-down spontaneously due to being radioactive.
- Elements are listed in the periodic table.
24
Q
What is meant by Energy State in Chemistry?
A
The position and energy of an electron described by its quantum numbers is known as its energy state.
25
Explain how an ionic compound forms (using the example of magnesium and chlorine to form MgCl2)
When magnesium atoms react with each chlorine atoms the magnesium atoms lose two electrons forming Mg2+ because it gives them to each of the two chlorine atoms, that gain one electron, each forming 2 Cl- ions
26
explain why atoms of an element may have different mass numbers?
they may have different numbers of neutrons
27
What does the Heisenberg Uncertainty Principle state?
The **Heisenberg uncertainty principle** states that it is impossible to know simultaneously the exact position and momentum of a particle. That is, the more exactly the position is determined, the less known the momentum, and vice versa.
28
how are ions detected in a mass spectrometer?
when the positive ions collide with the detector, they accept an electron which generates an electrical current.
29
How are metals good conductors of heat?
If you heat one end of the metal the energy is picked up by the delocalised electrons and as the electrons move around in the metal the heat energy is transferred throughout the structure.
30
How are the layers in graphite easily removed?
Although the forces holding the atoms together in each layer are very strong, the actual forces between the layers are much weaker. The layers are relatively far apart.
31
How can compounds form?
Energy transfer
32
How can you break an ionic compound?
Provide enough energy
33
How do you know how many protons are in an element based upon what you see in the periodic table?
Check the atomic number
34
How do you work out the number of shells with the period number?
Moving across each period, you can see that the number of shells is the same as the period number. For example if it is the 1st period then it will only have 1 shell or if it is the 4th periods it will have 4 shells.
35
How does one calculate the atomic mass of a number?
Multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.
36
How many bonds can an atom form?
As many bonds as there are electrons in its outermost shell.
37
How many carbon atoms is each carbon atom bonded to in graphite and what does this mean?
3, that there is a delocalised electron
38
How many electrons are you allowed on the 3rd shell?
8
39
How many other carbon atoms is each carbon atom bonded to in diamond?
4
40
How would you draw an ionic structure, e.g. NaCl
Draw two particles in the key, e.g. Na+ as a black dot and Cl- as a blank dot.Draw lots of cubes with a particle on each corner, make sure there are never any two Na+ connected by lines and visa versa.
41
What does Hund's Rule state?
1. Every orbital in a sublevel is singly occupied before any orbital is doubly occupied.
2. All of the electrons in singly occupied orbitals have the same spin.
42
identify the block in the periodic table to which magnesium belongs?
s block
43
If oxygen gains 2 electrons through ionic bonding will it be (2-) or (2+)? Why?
(2-) because electrons have a negative charge.
44
in a mass spectrometer, why is it necessary to ionise atoms before acceleration?
if the particles are not charged they cannot be attracted to and accelerated by a charged plate
45
In a simple molecule what do you have to break to melt the substance?
Intermolecular forces of attraction
46
Ion
An atom that loses or gains an electron and changes its charge.
47
What is an ion?
An atom or group of atoms which carries an elecrical charge, either positive or negative.
48
Describe an ionic crystal shape
Giant three-dimensional regular lattice structure
49
Give an example of a giant ionic structure
Sodium chloride. NaCl
50
Is an atom more or less reactive with a full outer shell? Why?
LessBecause there is no room for reactions to take place if the outer shell is full.
51
Is graphite more or less dense than diamond? Why?
Graphite is less dense because the layers in graphite are relatively far apart. In a sense a graphite chrystal contains a lot of wasted space which there isnt in a diamond.
52
Is the atom more reactive with a full outer shell or less reactive?
Less reactive.
53
Because isotopes of an element have different numbers of neutrons, they also have different ____ \_\_\_\_\_\_\_.
mass numbers
54
Isotopes
For an element, multiple species of atoms with the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers) exist; these are called isotopes of the element.Isotopes are referred to either by the convention described above or, more commonly, by name of the element followed by the mass number. Like carbon-12 and carbon-14.Almost all elements exist as a collection of two or more isotopes.
55
Isotopes are...
Atoms with different numbers of neutrons e.g. Chlorine
56
What are the main points of **John Dalton's Atomic Theory** (1808)?
1. The elements are made of atoms, which are tiny particles, too small to see.
2. All atoms of a particular element are identical.
3. Atoms of different elements have different properties: their masses are different, and their chemical reactions are different.
4. Atoms cannot be created, destroyed or split.
5. In a chemical reaction, atoms link to one another, or separate from one another.
6. Atoms combine in simple whole-number ratios to form compounds
57
Key differences between mixtures and compounds:
• Compounds are in fixed proportions, mixtures aren't.• In a mixture of elements, the elements still have their own properties. But elements in a compound will not retain the same properties.• Mixtures can be separated by physical means, for compounds you must change them chemically to separate them.• There are no energy changes involved in a mixture where as when compounds are made energy is released.
58
Li 3 7 If you have lithiums structure like this, how many electrons will be on the outer shell?
1 on the outer shell
59
Magnetic Quantum Number (ml)
Third quantum number. Describes the orientation of the orbital in space. An orbital is a specific region within a subshell that may contain no more than two electrons. THe magnetic quantum number specifies the particular orbital within a subshell where an electron is highly likely to be found at a given point in time. The possible values are all integers from l to -l, including 0. Therefore, the s subshell, where there is one possible value of ml (0), will contain one orbital; likewise, the p subshell will contain three orbitals, the d subshell will contain five orbitals, and the f subshell will contain seven orbitals. The shape and energy of each orbital are dependent upon the subshell in which the orbital is found. For example, a p subshell has three possible ml values (-1, 0, +1). The three dumbell shaped orbitals are oriented in space around the nucleus along the x, y, and z axes and are often referred to as px, py, and pz.
60
define the term mass number of an element?
the total number of protons and neutrons in the nucleus of an atom
61
What is the Mass Number of an atom?
The **Mass Number** of an atom is the **total number** of
**protons** and **neutrons** it contains *(all of which are located in the nucleus of the atom)*.
* The **Mass Number** of an atom is represented by the symbol **A**.
* The **Mass Numbe**r of an atom is also known as the **Nucleon Number**.
62
Describe the diagram of a metallic bond
Layers of positively charged ions surrounded by a 'sea' of delocalised electrons Layers of ions in a giant structurei.e. circles with plus signs in with a label around saying sea of delocalised electrons
63
What is 'the mole' in chemistry?
* IThe "mole" is a number scientifically determined such that when you have 1 mole of nucleons (either protons or neutrons or both), it weighs exactly 1 gram. There is a near perfect correlation between the total number of nucleons in an atom and how many grams 1 mole of those atoms weighs.
* The number is Avogadro's number (constant) , 6.022 x 1023 particles.
## Footnote
*For example, the atomic weight of carbon is 12.0g/mol, which means that 6.022x1023 carbon atoms weigh 12.0g.*
64
Give an example of a simple molecular structure
H2O
65
What are the **properties** of **simple molecular structures?**
* Contain only a few atoms held together by strong covalent bonds - *An example is carbon dioxide (CO2), the molecules of which contain one atom of carbon bonded with two atoms of oxygen.*
* Low melting and boiling point - *This is because the weak intermolecular forces break down easily.*
* Non-conductive - *Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge.*
* Tend to be insoluble to water - *Those which do dissolve often react with the water, or else are capable of forming hydrogen bonds with the water.*
* Often soluble in organic solvents
66
What is a molecule?
* A molecule is a group of atoms held together by covalent bonds
* A molecule is the smallest unit (particle) of a compound that has the physical and chemical properties of that compound.
67
What is the relative mass of a neutron?
1
68
List 6 key facts about Neutrons.
* Neutrons are located in the nucleus of atoms, together with the protons in the atom.
* Neutrons have zero charge. Another way to state the same thing is to say that neutrons are "charge neutral".
* Neutrons have a relative mass of 1, which is the same as the relative mass of protons.
* The number of neutrons in an atom may be calculated from the atomic number of that atom (element) and the mass number of that atom (isotope). Number of Neutrons (in an atom) = Mass Number (A) - Atomic Number (Z)
* Protons and neutrons are collectively referred to as nucleons.
* Neutrons are responsible for about half the weight of conventional matter by volume.
* Neutrons play important roles in nuclear power production.
69
The number of neutrons in an atom is the difference between the ____ \_\_\_\_\_\_ and ______ \_\_\_\_\_\_.
mass numberatomic number
70
When was the neutron first discovered? *and* Who discovered the neutron?
The neutron was discovered in 1932 by James Chadwick who was working at Cambridge University, England.
71
Are neutrons electrically charged or neutral.
Neutrons are neutral.
72
What does the nucleus contain?
Protons and neutrons
73
Which 2 particles are found in the nucleus?
Protons and neutrons.
74
Orbital FIlling
To determine which subshells are filled, you must know the number of electrons in the atom. In the case of uncharged atoms, the number of electrons equals the atomic number. If the atom is charged, the number of electrons is equal to the atomic number plus the extra electrons if the atom is negative, or the atomic number minus the electrons if the atom is positive.
75
Orbitals
The most important difference between the Bohr model and modern quantum mechanical models is that Bohr's assumption that electrons follow a circular orbit at a fixed distance from the nucleus is no longer considered valid. Rather, electrons are described as being in a state of rapid motion within regions of space around the nucleus, called orbitals.An orbital is a representation of the probability of finding an electron within a given region.
76
Paramagnetic and Diamagnetic
The presence of paired or unpaired electrons affects the chemical and magnetic properties of an atom or molecule. If the material has unpaired electrons, a magnetic field will align the spins of these electrons and weakly attract the atom. These materials are said to be paramagnetic.Materials that have no unpaired electrons and are slightly repelled by a magnetic field are said to be diamagnetic.
77
Principal Quantum Number (n)
This is the quantum number used in Bohr's model that can theoretically take on any positive integer value. The larger the integer value of n, the higher the energy level and radius of the electron's orbit. The max number of electrons in energy level n (electron shell n) is 2n^2.The difference in energy between adjacent shells decreases as the distance from the nucleus increases, since it is related to the expression (1/n2^2)-(1/n1^2).For example, the energy difference between the 3rd and 4th shells (n=3 to n=4) is less than that between the 2nd and 3rd shells (n=2 to n=3).
78
What is the electrical charge of a proton?
Positive
79
What is the relative mass of a proton?
1
80
List 5 **key facts** about **protons**.
* Protons are located in the nucleus of atoms, together with any neutrons also present in the atom.
* Protons have a positive (+1) charge, which balances the negative (-1) charge of the electrons that surround the nuclei of atoms.
* Protons have a relative mass of 1, which is the same as the relative mass of neutrons.
* The number of protons in an atom is called the "Atomic Number" of that atom and is sometimes referred to as "Z". This is important because it defines the type of atom, i.e. which element it is an atom of.
* Protons and neutrons are collectively referred to as nucleons.
81
When was the proton first discovered? and
Who discovered the proton?
In 1886 Eugen Goldstein discovered "canal rays" (also known as "anode rays") which he showed to be positively charged particles (ions) produced from gases - but those from different gases had different values of charge-to-mass ratio (e/m), so they could not be identified with a single particle.
82
Quantum Numbers
Modern atomic theory states that any electron in an atom can be completely described by four quantum numbers. n, l, me, and ms. Furthermore, according to the Pauli exclusion principle, no two electrons in a given atom can possess the same set of four quantum numbers.
83
Quantum Theory
Proposed by Max Planck in 1900. Proposed that energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta. The energy value of a quantum is given by the equation E=hf, where h is a proportionality constant known as Planck's constant, equal to 6.626x10-34 Jxs, and f (sometimes designated v) is the frequency of the radiation.
84
How do you calculate the Relative Atomic Mass (*A*r) (Atomic Weight) of an element?
The relative atomic mass (*A*r) of an element represents the average mass of one atom, taking into consideration the number of **isotopes** of the element, their relative isotopic mass (RIM) and their relative abundance. Using data from the mass spectrum, one could calculate the relative atomic mass for an element by using the following method of calculation:
85
1. What is the **Atomic Number**?
2. What is the **Mass Number**?
3. How is an element recorded on the **periodic table**?
4. What is an **Isotope**?
1. The atomic number (symbol ***Z***) is the number of protons in the nucleus of an atom.
2. The mass number (symbol ***A***) is the number of protons and neutrons added together.
3. See Image
4. An **isotope** is a form of an element with the same number of protons but **different** **numbers** of **neutrons** in the nucleus
86
Simple physical properties of a metal:
Metals tend to be strong high melting and boiling point.
87
Simple properties of giant covalent compounds?
Very hardVery high melting and boiling pointDo not conduct electricity (except graphite)Does not dissolve in water or any solvent
88
Spin Quantum Number (ms)
Fourth quantum number. The spin of a particle is its intrinsic angular momentum and is a characteristic of a particle, like its charge. In classical mechanics, an object spinning about its axis has an angular momentum; however, this doesn't apply to the electron. Classical analogies often are inapplicable in the quantum world.In any case, the two spin orientations are designated +1/2 and -1/2.Whenever two electrons are in the same orbital, they must have opposite spins. Electrons in different orbitals with the same ms values are said to have parallel spins.The quantum numbers for the orbitals in the second principal energy level, with their max number of electrons noted in parentheses, are shown in the following table. Electrons with opposite spins in the same orbital are often referred to as paired.
89
state and explain the difference, if any, between the chemical properties of the isotopes 113In and 115In
nonethey have the same electron configuration
90
state and explain the general trend in first ionisation energies for the period 3 elements aluminium to argon?
increasesthe nuclear charge increases whilst the amount of shielding remains the same
91
state the meaning of the term mass number of an isotope?
the total number of protons and neutrons in the nucleus of an atom
92
state the two measurements that are recorded for each isotope on the mass spectrum?
its m/z ratio and relative abundance
93
The columns are known as...
Groups
94
The rows are known as...
Periods
95
The Rutherford atomic model: the atom is mostly \_\_\_\_\_. Most of the ____ is in a very small region at the center.
emptymass
96
The Rutherford atomic model: the electrons are distributed ______ the nucleus and occupy almost all the ______ of the atom.
aroundvolume
97
The Rutherford atomic model: the protons and neutrons are located at the \_\_\_\_\_\_\_.
nucleus
98
True or false: The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means atoms have no overall electrical charge.
True.
99
True or false? You can have 8 electrons on the first shell
FALSE
100
What can Atomic Absorption Spectroscopy be used to measure the concentration of metals in :
* mining operations and in the production of alloys as a test for purity
* contaminated water, especially heavy metal contamination in industrial waste water
* organisms, such as mercury in fish
* air, eg lead
* food
101
What 3 particles make up the centre of an atom?
Electrons, protons and neutrons.
102
What are 5 key facts about compounds?
* Compounds consist of molecules formed from atoms of 2 or more different elements bound together chemically.
* Compounds can be broken down into a simpler type of matter (elements) by chemical means; not by physical means
* Compounds always contains the same ratio of component elements.
* Compounds have properties different from their component elements
* e.g. the compound water (H2O) is a liquid at room temperature and pressure and has different chemical properties from those of the two elements, hydrogen (H2) and oxygen (O2), from which it is formed.
* Compounds can be represented using chemical formulae.
103
What are isotopes?
Atoms with the same element with different numbers of neutrons
104
What are properties that ionic compounds have?
High melting pointHigh boiling point Dissolve easily in water (They are soluble)
105
what are the 4 stages of the mass spectrometer?
ionisation, acceleration, deflection + detection
106
What are the forces of attraction between layers of graphite like?
Weak
107
what are the names of positive and negative ions?
a positive ion is a cationa negative ion is an anion
108
What are the three types of subatomic particles?
Electrons, protons, and neutrons.
109
What are you finding out the number of if you take away the atomic number away from the atomic mass?
The number of neutrons.
110
What do all elements in group 0 have in common?
They all have a full outer shell
111
Why do giant covalent structures have such a high melting point
Because to melt it you need to break every covalent bond in the giant structure
112
What does a carbon dioxide dot and cross diagram look like?
two oxygens covalently bonded to carbon, both with double covalent bonds.
113
What does a full outer shell make the atom more?
Stable
114
What does an ethene dot and cross diagram look like?
two carbons with a double covalent bond and then each carbon respectively bonding with two hydrogens, single bond.
115
What does an nitrogen dot and cross diagram look like?
two nitrogens with a triple covalent bond.
116
What does ductile mean?
Can easily side over each other and be drawn into wires
117
What does the Atomic Number of a chemical element tell us?
* The Atomic Number uniquely identifies a chemical element.
* The Atomic Number of an atom is represented by the symbol Z.
* The number of protons in an atom is also (sometimes) called the Proton Number.
* Each element has its own Atomic Number (number of protons).
* Because atoms are neutral (that is neither positive "+ve" nor negative "-ve"), and protons have a charge of +1 while electrons have a charge of -1, the number of protons in an atom = the number of electrons in the atom.
* The Atomic Number is therefore also the number of electrons in an atom.
118
What does the atomic number tell you?
The number of protons and electrons.
119
What does the Periodic Table allow you to do?
Easily compare the properties of one element (or a group of elements) to another element (or groups of elements).
120
What does the shell contain
Electrons
121
What experiment tested to see whether protons/elections were arranged or randomized?
Rutherford's Gold-Foil Experiment
122
what forces holds together protons and electrons?
electrostatic forces
123
What formula do alkenes follow?
CnH2n
124
What happens to the bonds when you melt or boil a substance made of molecules?
You are breaking the intermolecular forces NOT the covalent bonds. When you boil water you get steam, not a mixture of hydrogen and oxygen atoms. The covalent bonds within the molecule remain (it is still H2O)
125
What happens when there is:1) A loss of electrons?2) A gain of electrons?
1) In a reaction with a non-metal, each alkali metal atom loses its outer electron and becomes an ion with a single positive charge, +1.2) In a reaction with a metal, each halogen atom gains an outer electron and becomes an ion with a single negative charge, -1.
126
What is a atom of the same element with different numbers of neutrons called
Isotope
127
What is a covalent bond?
A shared pair(s) of electrons between 2 atoms. There is an attractive force between the pair of electrons and the protons in the nuclei of the atoms involved in forming the bonds.
128
What is a diatomic molecule?
One that contains two atoms.
129
What is a lattice?
A regular array of particles.
130
what is adjusted in order to direct ions of different mass to charge ratio onto the detector?
the strength of the magnetic field
131
What is an alloy? Give some examples:
An alloy is a mixture of metals. Brass is an alloy of copper and zinc, stainless steel is an alloy of iron, chromium and nickel.
132
What is an intermolecular force?
The forces of attraction between separate molecules. They can be repulsive.
133
What is graphene?
One layer of graphite
134
What is ionic bonding?
Bonding in which there has been a transfer of electrons from one atom to another to produce ions. The substance is held together by strong electrical attractions between positive and negative ions.
135
what is meant by the term first ionisation energy?
energy required for the removal of one electron from a gaseous atom
136
What is metallic bonding?
The electrostatic force of attraction between positive metal ions and the sea of delocalised electrons
137
What is the atomic number of an atom? A) The number of protons and electrons it contains. B) The number of protons it contains. C) The number of electrons it contains.
B) The number of protons it contains.
138
What is the cluster of neutrons and protons in the centre of the atom called?
The nucleus
139
what is the definition of an isotope?
atoms of the same element with the same number of protons, but different numbers of neutrons
140
What is the force of attraction between the metallic ions and delocalised electrons?
Electrostatic force of attraction
141
What is the general formula for an unsaturated compound?
CnH2n
142
What is the general formula for saturated compound?
CnH2n+2
143
what is the relative charge of a neutron?
0
144
what is the relative charge of a proton?
+1
145
what is the relative charge of an electron?
-1
146
what is the relative mass of an electron?
1/1/1840
147
what is used in a mass spectrometer to accelerate the positive ions?
a charged plate
148
what is used to ionise a gaseous sample in a mass spectrometer
an electron gun
149
What would happen if you subjected a metal to a large force
The particles slide over each other and stay in their new positions.
150
What would happen if you subjected a metal to a small force?
It will stretch and return to its original position, it is elastic.
151
When can ionic substances conduct electricity and why?
When they are molten or in a solution (liquid) because the positive and negative ions are free to move so can carry an electric current.
152
When can ionic substances not conduct electricity and why?
When they are solid because the ions are locked together in a lattice/giant structure so the ions (which would be the charge carriers) are not free to move in a fixed regular structure
153
When writing the symbol for a metal in exams such as sodium, should you write Na or Na+?
Thinking about the structure as a whole you write Na as the number or electrons balances the number of positive charges. The metal as a whole has no charge.
154
Why are ionic substances usually soluble in water?(May be extra)
The electrons in the bonds are attracted towards the oxygen end of the bond. This makes the oxygen slightly negative leaving the hydrogen slightly short of electrons and therefore slightly positive. Because of this distortion water is described as a polar molecule. There are quite strong attractions between the polar water molecules and the ions in the lattice. The slightly positive hydrogens in the water molecules cluster around the negative ions and the slightly negative oxygens are attracted to the positive ions.
155
Why are metals good conductors of electricity?
Because they have a sea of delocalised electrons that are free to move where current can pass through
156
Why are metals malleable?
The layers of ions can slide over each other easily.
157
Where are protons and neutrons found in an atom?
They are found in the nucleus.
158
Why do ionic substances have a high melting point?
Because it is a giant ionic structure so more energy is required to break the attractive forces (electrostatic forces of attraction) between the positively and negatively charged ions.
159
Why do metals have a high melting point?
Because more energy is needed to break the strong electrostatic forces of attractions (bonds) between the metal ions and sea of delocalised electrons.
160
Why do simple molecular substances have low melting points?
Because only enough energy is needed to break the weak intermolecular forces between molecules
161
Why doesn't diamond conduct electricity?
All the electrons in the outer levels of the carbon atoms are tightly held in covalent bonds between the atoms. None are free to move around.
162
Why don't covalent bonds conduct electricity?
Because there are no charged particles free to move
163
Why is graphite a good conductor of electricity?
Because of the delocalised electrons that haven't been used and the current can pass through
164
Why is there a stronger force of attraction between MgO than NaCl?
It is mg2+O2- so there is a stronger force of attraction between the oppositely charged ions. Because there are larger opposite charges
165
Why isn't magnesium oxide, an ionic substance, soluble in water?
Magnesium ions are Mg+ and oxygen ions are O2- meaning they have stronger attractions between the positively and negatively charged ions. The water molecules are not strong enough to break these bonds.
166
write an equation to show the process that occurs when the second ionisation energy of aluminium is measured?
Al+(g) → Al2+(g) + e−
167
write an equation, including state symbols, to show the process that occurs when the first ionisation energy of rubidium is measured?
Rb(g) → Rb+(g) + e−
