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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
Q

What does the period number tell you about all the elements in that period?

A

Elements in the same period have the same number of electron shells

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26
Q

What does the group number tell you about all the elements in that group?

A

They will have the same number of outer electrons

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27
Q

On which side of the periodic table are the metals positioned?

A

On the left

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28
Q

Hat determines whether an element is a metal or non-metal?

A

The atomic structures of the elements

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29
Q

What is the maximum number of electrons allowed in each of the first three shells?

A

1: 2
2: 8
3: 8

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30
Q

When are atoms most stable?

A

When they have full electrons shells

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31
Q

What is an ionic bond?

A

A bond between a metal and non-metal involving the transfer of electrons

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32
Q

In terms of electrons, describe what happens to the metal and non-metal when an ionic bond forms

A

The metal atom loses electrons to become a positively charged ion
The non-metal gains electrons to become a negatively charged ion

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33
Q

What is an ion?

A

An atom or group of atoms with a positive or negative charge

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34
Q

If an ion is positively charged, has it lost or gained electrons?

A

It has lost them

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35
Q

Why do elements in groups 1,2,6 and 7 readily form ions?

A

So they become more stable and achieve the electron structure of the noble gases

36
Q

What type of ions do elements in group 1 and 2 form?

A

Cations (positive)

37
Q

What type of ions do elements in groups 6 and 7 form?

A

Anions (negative)

38
Q

What does it mean if an ionic compound ends in -ide?

A

The compound contains 2 elements

39
Q

What does it mean if an ionic compound ends in -ate?

A

The compound contains at least three elements, one of which is oxygen

40
Q

Describe the structure of an ionic compound

A

Lattice structure
Regular arrangement of ions
Ions held together by strong electrostatic forces between ions with opposite charges

41
Q

What is a covalent bond?

A

A bond formed when an electron pair is shared between two atoms

42
Q

What forms as a result of covalent bonding?

A

A molecule

43
Q

Are covalent bonds weak?

A

No, they are very strong

44
Q

Which is smaller, an atom or a molecule?

A

An atom

45
Q

Why do ionic compounds have high melting points?

A

Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome

46
Q

When do ionic compounds conduct electricity? And why?

A

When molten or aqueous because the ions are charged and free to move

47
Q

Why do simple molecular compounds have low melting and boiling points?

A

They have weak intermolecular forces which only require a little energy to overcome

48
Q

Do simple molecular compounds conduct electricity? Why?

A

No because there are no charged particles

49
Q

Do giant covalent structures have a high melting point? Why?

A

Yes because they have lots of strong covalent bonds which require a lot of energy to break

50
Q

How do metals conduct electricity and heat?

A

The positive ions are fixed in a sea of delocalised electrons which are free to move and carry charge

51
Q

Are metals insoluble in water?

A

Yes

52
Q

Name two giant covalent structures formed from carbon atoms

A

Graphite

Dimond

53
Q

Describe the structure of graphite

A

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
Q

Describe and explain the properties of graphite

A

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
Q

Describe the structure of a dimond

A

All carbon atoms are covalently bonded to four other carbon atoms
There are no delocalised electrons

56
Q

Describe the properties of dimond

A

Very hard
Very high melting point
Doesn’t conduct electricity as there are no charged particles

57
Q

What are the uses of graphite? Why?

A

Electrodes because graphite conducts electricity and has a high melting point
Lubricant because it is slippery

58
Q

Why is dimond used in cutting tools?

A

It is very hard

59
Q

What is a fullerene?

A

A fullerene is a molecule made of carbon, shaped like a closed tube or hollow ball

60
Q

Name two fullerenes

A

Graphen

C60 (buckminsterfullerene)

61
Q

What are the properties of the fullerene C60?

A

Slippery sir to weak intermolecular forces
Low melting point
Spherical
Strong covalent bonds between carbon atoms in a molecule
Large surface area

62
Q

What are the properties of graphemes?

A

High melting point due to covalent bonding between carbon atoms
Conducts electricity because it has delocalised electrons

63
Q

Why is Graphene useful in electronics?

A

It is extremely strong and has delocalised electrons which are free to move and carry charge
It is only one atom thick

64
Q

What is a polymer?

A

Long chain molecules formed from many monomers

65
Q

What bond is formed between carbon atoms in polymer molecules?

A

Covalent bonds

66
Q

What are the properties of metals?

A 
High. Elating point
High density
Good conductors of electricity
Malleable and ductile
Generally shiny
67
Q

Explain why metals are malleable

A

The atoms are arranged in uniform rows which can slide over one another

68
Q

Explain why metal can conduct electricity

A

The electrons in the metal are charged that can move

69
Q

What are the properties of non-metals?

A

Low boiling points
Poor conductors of electricity
Brittle when solid

70
Q

What is a limitation of a dot and cross diagram when representing ionic compounds

A

No lattice structure of ionic bonds

71
Q

What are the limitations of 2D diagrams to represent ionic compounds

A

Only shows one layer, doesn’t show formation of ions

72
Q

What are the limitations of 3D diagrams when representing ionic compounds

A

They don’t show spaces between the ions

Doesn’t show charges

73
Q

What are the limitations of dot and cross diagrams when representing covalent molecules?

A

They don’t show relative sizes of atoms or intermolecular forces

74
Q

What are the limitations of the ball and stick model when representing covalent molecules?

A

Bonds shown as sticks rather than forces

Don’t show how the covalent bonds form

75
Q

How do you calculate the relative formula mass of a compound?

A

Add together all of relative atomic masses of the atoms in the compound

76
Q

What is the empirical formula?

A

The smallest whole number ratio of the atoms of each element in a compound

77
Q

What is the molecular formula?

A

Actual number of atoms of each element in a compound

78
Q

Describe an experiment to work out the empirical formula of magnesium oxide

A

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
Q

What is the law of conservation of mass?

A

No matter is lost or gained during a chemical reaction

80
Q

If a reaction is carried out in a closed system, what can you say about the total mass of the reaction throughout the experiment?

A

The mass stays constant

81
Q

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?

A

The mass decreases as the gas escapes

82
Q

What equation links mass, moles and relative atomic mass?

A

Mass = molesxrelative atomic mass

83
Q

How can you calculate concentration?

A

Concentration = mass/volume

84
Q

What is the avogadro constant?

A

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
Q

What formula links the Avogadro constant, moles and number of particles?

A

Number of particles = Avogadro constant x moles

86
Q

What is a limiting reactant in a chemical reaction?

A

The chemical that is used up first in a reaction, preventing the formation of more product

Chemistry (8 decks)

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