Topic 1 - Key Concepts in Chemistry Flashcards
1
Q
What are uses of diamonds?
A
Cutting tools
2
Q
What type of ions do elements in group 1 and 2 form?
A
- Cations (Positive ions): Group 1 metals form +1 ions
- Group 2 metals form +2 ions
3
Q
Are metals insoluble in water?
A
Yes
4
Q
Why was Mendeleev’s table not always accurate in the order of increasing relative atomic mass?
A
Because isotopes were poorly understood at time and protons and neutrons were yet to be discovered
5
Q
What are limitations of 3D models when representing ionic compounds?
A
Shows spaces between ions and doesnt show charge
6
Q
How are elements arranged in modern periodic table?
A
In order of increasing atomic number in rows called periods
7
Q
What is relative mass of an electron?
A
Very small (roughly 1/1800)
8
Q
What equation links mass, moles and relative atomic mass?
A
Mass (g) = Moles x Relative Atomic Mass (Mr)
9
Q
What does it mean if an ionic compound ends in -ide?
A
It usually contains two elements
10
Q
How is the electronic configuration of an element related to its position in the periodic table?
A
- Number of shells is period (row)
- Number of electrons in outer shell is group (column)
- Number of electrons is atomic number
11
Q
Why is the relative atomic mass of an element not always a whole number?
A
- Different isotopes of the same element have different mass numbers.
- The relative atomic mass is average of masses of all isotopes
12
Q
Explain why metals are malleable
A
Atoms arranged in uniform rows that can slide over each other
13
Q
How did Dmitri Mendeleev used his periodic table to predict the existence and properties of some undiscovered elements?
A
Used properties of elements next to gaps to predict properties of undiscovered elements
14
Q
How many atoms are in 3 moles of copper?
A
Number of atoms/particles = Avogadro’s constant x Moles
= (6.02 x 10^23 ) x 3
= 1.81 x 10^24
15
Q
What is the empirical formula for Fe2O4?
A
FeO2
16
Q
What is the atomic number of an element?
A
The number of protons in an atom
17
Q
Why does graphene conduct electricity?
A
It has delocalised electrons
18
Q
What is the atomic structure of metals?
A
- Form positive ions
- Usually good conductors
- High melting and boiling points
- Ductile
- Malleable
19
Q
What is an isotope?
A
Different atoms of the same element containing the same number of protons but different numbers of neutrons in their nuclei
20
Q
Describe the structure of an ionic compound
A
Lattice structure consisting of a regular arrangement of ions held together by strong electrostatic forces (ionic bonds) between oppositely charged ions
21
Q
What is relative formula mass of CO 2 (C - 12) (O-16)
A
12+16+16 = 44
22
Q
What is the properties of non-metals?
A
- Form negative ions
- Insulators
- Low melting and boiling points
23
Q
Name two fullerenes?
A
- Graphen
- C60 (Buckminsterfullerene)
24
Q
How to calculate relative formula mass
A
Add together all relative atomic masses of atoms
25
What is an anion?
Negatively charged ion
26
Fill in the blank: Atoms of a given element have the same number of ________ in the nucleus and that this number is unique to that element
Atoms of a given element have the same number of **protons** in the nucleus and that this number is unique to that element
27
Put the following in order of size, a molecule, an atom
Atom , Molecule
28
Why do simple molecular compounds not conduct electricity?
They have no charged ions
29
52g of calcium reacts with oxygen to form 79g of calcium oxide, what mass of oxygen is needed?
79-52 = 27g
30
O^(2-) has atomic number of 8 and mass number 16, how many protons, electrons and neutrons does it have?
Protons - 8
Electrons - 10
Neutrons - 8
31
What are properties of metallic compounds?
* High melting and boiling points
* Malleable
* Good conductors of electricity and heat
* Insoluble in water
32
What did James Chadwick contribute to model of the atom?
Provided evidence to show existence of neutrons within nucleus
33
In terms of its electrons, describe what happens to the metal and non-metal when an ionic bond forms
* Metal atom loses electron(s) to become a positively charged ion - cation
* Non-metal atom gains electron(s) to become a negatively charged ion - anion
34
What was Earnest Rutherford's model of the atom?
Positively charged nucleus at centre surrounded by negatively charged electrons, mass concentrated at centre of atom - Nuclear model (1909)
35
Describe the experiment to work out the empirical formula of a simple compound such as magnesium oxide
* Weigh sample of magnesium
* Heat sample in crucible
* Weigh mass of magnesium oxide at end
* Calculate mass of oxygen (increase of mass)
* Calculate moles of magnesium and oxygen using experimental mass and relative atomic mass
* Work out whole number ratio of number of moles of magnesium to oxygen
* Use this to work out emperical formula
36
What are limitations of dot and cross models when representing covalent molecules
Doesn't show relative size of atoms or intermolecular forces
37
What is the mass number of an atom?
The sum of protons and neutrons in nucleus
38
How are metals malleable?
Atoms arranged in layers that can slide over each other
39
Boron has an atomic number of 5 and a mass number of 11, how many protons, neutrons and electrons does it have?
Protons - 5
Neutrons - 6
Electrons - 5
40
What is a polymer?
Large molecules containing chains of carbon atoms
41
How do you calculate concentration in g/dm^3?
concentration = mass of solute (g) / volume in dm^-3
42
Describe the structure of diamond
* Each carbon atom is covalntly bonded to four other carbon atoms
* There are no delocalised electrons
43
What was JJ Thompson's model of the atom?
A ball of positive charge with negative electrons embedded in it - Plum Pudding Model (1897)
44
What is the maximum number of electrons allowed in each of the first three shells of an atom?
* 1st shell - 2
* 2nd shell - 8
* 3rd shell - 8
45
What was Niels Bohr model of the atom
Electrons orbit nucleus at specific distances, electrons orbitted in fixed shells - Bohr Model (1913)
46
What are properties of non-metals?
* Low boiling points
* Poor conductors of electricity
47
Describe the structure of graphite
* Each carbon atom is bonded to three carbon atoms
* Form layers of hexagonal rings of carbon atoms
* Weak Intermolecular forces between layers
* One delocalised electron per carbon atom
48
What are properties of giant covalent compounds
* High melting and boiling points
* Don't conduct electricity when solid, molten or aqueous
49
Why do metallic compounds have high melting and boiling points
They have strong mettalic bonds
50
Why do elements in groups 1,2,6 and 7 form ions?
So they can get a full outer shell and be more stable
51
Why do ionic compounds only conduct electricity when molten or aqueous?
When solid, the ions are held in a fixed position in the lattice and are not free to move whereas whem molten or dissolved, lattice breaks apart and ions are free to move
52
Describe the nucleus of an atom compared to the overall size of the atom
Very small
53
Why are metals good conductors of electricity and heat?
* Positive ions fixed in sea of delocalised electrons.
* These electrons are free to move and carry charge
54
How is a covalent bond formed?
When a pair of electrons is shared between two atoms
55
What is the relative mass of a proton?
1
56
What is a fullerene?
Molecule made of carbon, shaped like closed tube or hard ball
57
What is Avogadro's constant?
The number of atoms, molecules or ions in one mole of a given substance
58
What is an atom?
Smallest part of element that can exist
59
Why is diamond used in cutting tools?
It is very hard due to its rigid structure
60
If an atom is positively charged, has it gained or lost electrons?
* Lost as there are fewer negative electrons to cancel out charge of protons.
* This means overalll charge is positive
61
Why do giant covalent compounds have high melting and boiling points
They have lots of covalent bonds which require lots of energy to break up the lattice
62
Why does graphene have a high melting point?
Strong covalent bonds between carbon atoms
63
What is a limiting reagent in a chemical reaction?
The chemical that is used up first in a reaction, preventing the formation of more product.
64
Cu + O2 -> CuO (not balanced) 127 g Cu react, 32g of oxygen react and 159g of CuO are formed. Work out the balanced equation using the masses given.
* moles = moles = mass/Mr
* Cu: moles = 127 / 63.5 = 2
* O2 : moles= 32 / (16 x 2) = 32/32 = 1
* CuO moles = 159 / (16 + 63.5) = 2
* Therefore you have ratio of 2:1:2 for Cu:O2 :CuO, making overall balanced equation 2Cu + O2 -> 2CuO
65
What are uses of graphite?
* Electrodes
* Lubricant
66
What type of ions do elements in groups 6 and 7 form?
* Anions (Negative ions): Group 6 non-metals form -1 ions
* Group 7 non-metals form -2 ions
67
What are limitations of dot and cross models when representing ionic compounds?
No lattice structure or ionic bonds
68
What is an example of a polymer?
Poly(ethene)
69
Where are metals found on periodic table?
To the left
70
What is a covalent bond?
A bond formed when atoms share a pair of electrons
71
Why is graphite used to make electrodes?
Graphite conducts electricity because there is one delocalised electron per carbon atom.
72
What are the properties of diamond?
* Very hard
* High melting point
* Doesn't conduct electricity
73
Explain why metals can conduct electricty?
Electrons in metals are charges that can move
74
What are examples of giant covalent structures formed from carbon atoms?
Diamond and Graphite
75
How do you get from cm^3 to dm^3
Divide by 1000
Eg 1000cm^3 = 1dm^3
76
What happens to the total mass of the reaction througout the experiment if it happens in a closed system?
The mass stays constant
77
Na^+ has atomic number of 11 and mass number 23, how many protons, electrons and neutrons does it have?
* Protons - 11
* Electrons - 10
* Neutrons - 12
78
Describe the structure of an atom
A nucleus containing protons and neutrons surrounded by electrons in a shell
79
What is the relative charge of a proton?
1
80
What is relative charge of electron?
-1
81
Why is C60 slippery?
Weak intermolecular forces
82
Why do simple molecular compounds have low melting and boiling points?
Molecules have weak intermolecular forces (forces between molecules) which require little energy to overcome
83
What happens to the total mass of the reaction througout the experiment if it happens in a open flask that takes in or gives out gas?
Mass decreases as gas escapes
84
What forms as a result of a covalent bonding?
A molecule
85
Where is most of the mass of an atom concentrated?
In the nucleus
86
What are limitations of ball and stick models when representing covalent molecules
Bonds shown as sticks rather than forces, doesn't show how covalent bonds form
87
What is the relative charge of a neutron?
0
88
What is a cation?
Positively charged ion
89
What is the mass of 20 moles of calcium carbonate CaCO3?
Mass = Moles x Relative Atomic Mass(Mr)
Mr = 100
Mass = 20x100
Mass = 2000g
90
How do you work out the relative atomic mass of an element when given relative masses and abundances of isotopes?
((% of isotope 1 x mass of isotope 1) + (% of isotope 2 x mass of isotope 2)) / 100
91
What is the value of Avogadro's constant?
6.02 x 10^23
92
What are properties of an ionic compound?
* High melting and boiling points
* Soluble
* Doesn't conduct electricity when solid
* Conducts electricity whem molten or dissolved
93
How are elements with similar properties organised in the periodic table?
Placed in same vertical columns called groups
94
What are properties of a simple molecular (covalent) compound?
* Low melting and boiling point
* Don't conduct electricity when solid, molten or aqueous
95
What does it mean if an ionic compound ends in -ate?
It usually contains three or more elements, one of which is always oxygen
96
Why do atoms contain equal number of protons and electrons?
In order to have an overall neutral charge
97
What is the stoichiometry of a reactoin?
Ratio of the amounts of each substance in a balanced equation
98
Where are metals found on periodic table?
To the left
99
Why is the mass of the product formed controlled by the mass of reactant which is not in excess?
* A reaction finishes when one of reactants is all used up and the other reactant has nothing left to react with.
* The reactant used up is called limiting reactant/reagant and the one left over is described as in excess
100
What is the empirical formula?
The smallest whole number ratio of the atoms of each element ina compound
101
What are the properties of C60?
* Slippery
* Low melting point
* Spherical
* Strong covalent bonds between carbon atoms
* Large surface area
102
What are limitations of 2D diagrams when representing ionic compounds?
Only show one layer, doesn't show formation of ions
103
What is the molecular formula
Actual number of atoms of each element in a compound
104
What values can be used to calculate empirical formula of a simple compound?
* Reacting masses
* Percentage composition
105
What is relative mass of a neutron?
1
106
What is an ionic bond?
A bond between a metal and non-metal involving transfer of electrons
107
The atomic number of Na (Sodium) is 11. What is the electronic configuration of Na?
2.8.1
108
What is an ion?
An atom or group of atoms with a positive or negative charge
109
Why is graphite used as a lubricant and in lead
It is soft/slippery because there are weak intermolecular forces between layers allowing the layers to slide over each other
110
What are properties of metals?
* High melting point
* High density
* Good conductors of electricity
* Malleable
* Ductile
* Generally shiny
111
What formula links Avogadro;s constant, moles and number of particles?
Number of particles = Avogadro's constant x Moles
112
What is the law of conservation of mass
No atoms/matter is lost or gained during a chemical reaction
113
How did Dimitri Mendelee arange known elements at the time
* Elements arranged in order of atomic number
* Elements with similar properties put into columns called groups (due to periodic trends in chemical properties)
* Elements in same group have same number of outer shell electrons
* Elements in same row (period) have same number of electron shells
* Switched position of some elements
* Left gaps for unknown elements
114
Why do giant covalent bonds not conduct electricity?
They have no charged ions
115
Why do ionic compounds have high melting and boiling points?
Strong electrostatic attraction between the positive and negative ions, requires a lot of energy to overcome
116
What are properties of graphene?
* High melting point
* Conducts electricity
* Very strong
* One atom thick
117
What was Dalton's model of the atom?
Tiny solid spheres that could not be divided made up the different elemnts (Pre 1900)
