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Chemistry > Topic 1 - key concepts > Flashcards

Topic 1 - key concepts Flashcards

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1
Q

What are the three ideas in John Dalton’s theory about the atom?

A

Atoms cannot be created, divided or destroyed
Atoms of the same element are exactly the same and atoms of different elements are different
Atoms join with other atoms to make new substances

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2
Q

What discovery caused the oriGina dalton model of an atom to change?

A

The discovery of subatomic particles

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3
Q

How did JJ Thomson discover the electron?

A

Tho pain experimented with a cathode ray tube

The beam moved towards the positively charged plate so we knew that the particles must have a negative charge

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4
Q

Describe the atomic model proposed by JJ Thomson

A

Plum pudding model

Negatively charged electrons scattered through a positively charged material

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5
Q

What did Ernest Rutherford discover from his gold foil experiment?

A

He shot a beam of positively charged particles at sheet of gold foil
Most particles passed straight through suggesting that atoms were mostly empty space
A few particles were deflected and a few bounced directly back showing that there must be a tiny dense and positively charged nucleus

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6
Q

Describe rutherfors’s new model of the atom

A

Mass is concentrated in central nucleus
Mostly empty space
Electrons travel in random paths around the nucleus

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7
Q

Describe the structure of an atom

A

Small central nucleus made up of protons and neutrons

Electrons orbit the nucleus in shells

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8
Q

What is the radius of a nucleus?

A

1x 10^-14m

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9
Q

How large is a nucleus compared to the radius of an atom?

A

1/10000 of the atomic radius

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10
Q

What are the relative masses of protons, neutrons and electrons?

A

Proton: 1
Neutron: 1
Electron: 1/1850

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11
Q

What are the relative charges of protons, neutrons and electrons?

A

Proton: +1
Neutron:0
Electron:-1

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12
Q

Why do atoms contain equal numbers of protons and electrons?

A

Atoms are stable with no overall charge

Protons are positively charged and electrons are negatively so they must have the same number to balance the charge out

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13
Q

Where is the mass of an atom concentrated?

A

In the nucleus

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14
Q

What does the atomic number of an atom represent?

A

The number of protons

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15
Q

What does the mass number of an atom mean?

A

It is the number of protons and neutrons in the atom

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16
Q

What is an isotope?

A

Atoms of the same element that have a different number of neutrons

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17
Q

Why is the relative atomic mass not always a whole number?

A

Different isotopes have different mass numbers the the ram is an average

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18
Q

What two values would be required to calculate the relative atomic mass of chlorine?

A

The mass number and relative abundance’s of all the isotopes of chlorine

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19
Q

How did Mendeleev arrange the elements in his periodic table?

A

Elements were arranged with increasing atomic masses
The ones with similar properties were put into groups
He switched the position of some elements
He left gaps for undiscovered elements

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20
Q

How was Mendeleev able to predict the properties of new elements?

A

He left gaps in his periodic table

He used the properties of elements next to these gaps to predict the properties of undiscovered elements

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21
Q

Mendeleev’s table lacked some amount of accuracy in the way he’d ordered his elements, why?

A

Isotopes were poorly understood at the time

Protons and neutrons and not yet been discovered

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22
Q

How are elements arranged in the modern periodic table?

A

In order of increasing atomic number

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23
Q

What do elements in the same group have?

A

Similar chemical properties

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24
Q

Why do elements in the same column have similar chemical properties?

A

Same number of outer shell electrons

The number of outer shell electrons determines how an atom reacts

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25
What does the period number tell you about all the elements in that period?
Elements in the same period have the same number of electron shells
26
What does the group number tell you about all the elements in that group?
They will have the same number of outer electrons
27
On which side of the periodic table are the metals positioned?
On the left
28
Hat determines whether an element is a metal or non-metal?
The atomic structures of the elements
29
What is the maximum number of electrons allowed in each of the first three shells?
1: 2 2: 8 3: 8
30
When are atoms most stable?
When they have full electrons shells
31
What is an ionic bond?
A bond between a metal and non-metal involving the transfer of electrons
32
In terms of electrons, describe what happens to the metal and non-metal when an ionic bond forms
The metal atom loses electrons to become a positively charged ion The non-metal gains electrons to become a negatively charged ion
33
What is an ion?
An atom or group of atoms with a positive or negative charge
34
If an ion is positively charged, has it lost or gained electrons?
It has lost them
35
Why do elements in groups 1,2,6 and 7 readily form ions?
So they become more stable and achieve the electron structure of the noble gases
36
What type of ions do elements in group 1 and 2 form?
Cations (positive)
37
What type of ions do elements in groups 6 and 7 form?
Anions (negative)
38
What does it mean if an ionic compound ends in -ide?
The compound contains 2 elements
39
What does it mean if an ionic compound ends in -ate?
The compound contains at least three elements, one of which is oxygen
40
Describe the structure of an ionic compound
Lattice structure Regular arrangement of ions Ions held together by strong electrostatic forces between ions with opposite charges
41
What is a covalent bond?
A bond formed when an electron pair is shared between two atoms
42
What forms as a result of covalent bonding?
A molecule
43
Are covalent bonds weak?
No, they are very strong
44
Which is smaller, an atom or a molecule?
An atom
45
Why do ionic compounds have high melting points?
Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome
46
When do ionic compounds conduct electricity? And why?
When molten or aqueous because the ions are charged and free to move
47
Why do simple molecular compounds have low melting and boiling points?
They have weak intermolecular forces which only require a little energy to overcome
48
Do simple molecular compounds conduct electricity? Why?
No because there are no charged particles
49
Do giant covalent structures have a high melting point? Why?
Yes because they have lots of strong covalent bonds which require a lot of energy to break
50
How do metals conduct electricity and heat?
The positive ions are fixed in a sea of delocalised electrons which are free to move and carry charge
51
Are metals insoluble in water?
Yes
52
Name two giant covalent structures formed from carbon atoms
Graphite | Dimond
53
Describe the structure of graphite
Each carbon atom is bonded to 3 other carbon atoms There are layers of hexagonal rings of carbon atoms There are weak intermolecular forces between layers There is one delocalised electron per carbon atom
54
Describe and explain the properties of graphite
It is sold because there are only weak intermolecular forces between layers which allow the layers to slide over one another It conducts electricity because there is one delocalised electron per carbon atom. The delocalised electrons are mobile charges
55
Describe the structure of a dimond
All carbon atoms are covalently bonded to four other carbon atoms There are no delocalised electrons
56
Describe the properties of dimond
Very hard Very high melting point Doesn’t conduct electricity as there are no charged particles
57
What are the uses of graphite? Why?
Electrodes because graphite conducts electricity and has a high melting point Lubricant because it is slippery
58
Why is dimond used in cutting tools?
It is very hard
59
What is a fullerene?
A fullerene is a molecule made of carbon, shaped like a closed tube or hollow ball
60
Name two fullerenes
Graphen | C60 (buckminsterfullerene)
61
What are the properties of the fullerene C60?
Slippery sir to weak intermolecular forces Low melting point Spherical Strong covalent bonds between carbon atoms in a molecule Large surface area
62
What are the properties of graphemes?
High melting point due to covalent bonding between carbon atoms Conducts electricity because it has delocalised electrons
63
Why is Graphene useful in electronics?
It is extremely strong and has delocalised electrons which are free to move and carry charge It is only one atom thick
64
What is a polymer?
Long chain molecules formed from many monomers
65
What bond is formed between carbon atoms in polymer molecules?
Covalent bonds
66
What are the properties of metals?
``` High. Elating point High density Good conductors of electricity Malleable and ductile Generally shiny ```
67
Explain why metals are malleable
The atoms are arranged in uniform rows which can slide over one another
68
Explain why metal can conduct electricity
The electrons in the metal are charged that can move
69
What are the properties of non-metals?
Low boiling points Poor conductors of electricity Brittle when solid
70
What is a limitation of a dot and cross diagram when representing ionic compounds
No lattice structure of ionic bonds
71
What are the limitations of 2D diagrams to represent ionic compounds
Only shows one layer, doesn’t show formation of ions
72
What are the limitations of 3D diagrams when representing ionic compounds
They don’t show spaces between the ions | Doesn’t show charges
73
What are the limitations of dot and cross diagrams when representing covalent molecules?
They don’t show relative sizes of atoms or intermolecular forces
74
What are the limitations of the ball and stick model when representing covalent molecules?
Bonds shown as sticks rather than forces | Don’t show how the covalent bonds form
75
How do you calculate the relative formula mass of a compound?
Add together all of relative atomic masses of the atoms in the compound
76
What is the empirical formula?
The smallest whole number ratio of the atoms of each element in a compound
77
What is the molecular formula?
Actual number of atoms of each element in a compound
78
Describe an experiment to work out the empirical formula of magnesium oxide
Weigh a sample of magnesium Heat the sample in a crucible Weigh the mass of magnesium oxide at the end Calculate the mass of oxygen Calculate the moles of magnesium and oxygen using the experimental mass and relative atomic mass Work out the whole number ratio of the number of moles of magnesium to oxygen
79
What is the law of conservation of mass?
No matter is lost or gained during a chemical reaction
80
If a reaction is carried out in a closed system, what can you say about the total mass of the reaction throughout the experiment?
The mass stays constant
81
If a reaction is carried out in an open flask and a gas is produced, what can you say bout the total mass of the reaction throughout the experiment?
The mass decreases as the gas escapes
82
What equation links mass, moles and relative atomic mass?
Mass = molesxrelative atomic mass
83
How can you calculate concentration?
Concentration = mass/volume
84
What is the avogadro constant?
The number of atoms, molecules or ions in one mole of s given substance The value of it is 6.02 x 10^23
85
What formula links the Avogadro constant, moles and number of particles?
Number of particles = Avogadro constant x moles
86
What is a limiting reactant in a chemical reaction?
The chemical that is used up first in a reaction, preventing the formation of more product

Chemistry (8 decks)

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