Atomic Structure & the Perioic Table

Question 1

All substances are made of tiny particles of matter called

Answer 1

atoms which are the building blocks of all matter

Question 2

Each atom is made of subatomic particles called

Answer 2

protons, neutrons, and electrons

Question 3

The protons and neutrons are located at the centre of the atom, which is called

Answer 3

the nucleus

Question 4

The electrons move very fast around the nucleus in orbital paths called

Answer 4

shells

Question 5

The mass of the electron is

Answer 5

negligible, hence the mass of an atom is contained within the nucleus where the protons and neutrons are located

Question 6

a substance made of atoms that all contain the same number of protons and cannot be split into anything simpler.

Answer 6

element

Question 7

Elements take part in chemical reactions in which new substances are made in processes that most often involve an

Answer 7

energy change

Question 8

In these reactions atoms combine together in fixed ratios that will give them

Answer 8

full outer shells of electrons, often producing compounds

Question 9

A compound is a pure substance made up of two or more elements chemically …

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combined and which cannot be separated by physical means

Question 10

number of compounds is ///

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unlimuted

Question 11

Ionic compounds contain

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metal and non-metal elements joined together as particles called ions

Question 12

The non-metal element always takes on the name ending

Answer 12

‘– ide’ unless oxygen is also present,
For example, PbS is called lead sulfide and MgCl2 is called magnesium chloride

Question 13

When oxygen is present the name ending is usually

Answer 13

‘-ate’
For example, CuSO4 is copper sulphate, KClO3 is potassium chlorate and Na2CO3 is sodium carbonate

Question 14

The ending ‘-ite’ will always have

Answer 14

less oxygen than ‘-ate’

Question 15

H2SO4 is

Answer 15

sulfuric acid

Question 16

NH3

Answer 16

ammonia

Question 17

CH4

Answer 17

methane

Question 18

HCl

Answer 18

hydrochloric acid (or hydrogen chloride if it is a gas)

Question 19

C6H12O6

Answer 19

glucose

Question 20

C2H5OH

Answer 20

ethanol

Question 21

HNO3

Answer 21

nitric acid

Question 22

The reactants are those substances on the

Answer 22

left-hand side of the arrow and can be thought of as the chemical ingredients of the reaction

Question 23

The products are the new substances which are on the

Answer 23

right-hand side of the arrow
The arrow (which is spoken as “goes to” or “produces”) implies the conversion of reactants into products

Question 24

Reaction conditions or the name of a

Answer 24

catalyst (a substance added to make a reaction go faster) can be written above the arrow
An example is the reaction of sodium hydroxide (a base) and hydrochloric acid producing sodium chloride (common table salt) and water:
Sodium hydroxide + hydrochloric acid ⟶ sodium chloride + water

Question 25

S + O2 →

Answer 25

SO2
This equation shows that one atom of sulfur (S) reacts with one molecule of oxygen (O2) to make one molecule of sulfur dioxide (SO2)

Question 26

Nothing created - nothing

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destroyed
New substances are made during chemical reactions
However, the same atoms are always present before and after reaction
They have just joined up in different ways
Atoms cannot be created or destroyed, so if they exist in the reactants then they absolutely must be in the products!
Because of this the total mass of reactants is always equal to the total mass of products
This idea is known as the Law of Conservation of Mass

Question 27

The Law of Conservation of Mass enables us to

Answer 27

balance chemical equations, since no atoms can be lost or created
You should be able to:
Write word equations for reactions outlined in these notes
Write formulae and balanced chemical equations for the reactions in these notes

Question 28

Pb2+ + 2e- →

Answer 28

Pb

Question 29

2Br- →

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Br2 + 2e-

Question 30

Half equations are used to show what happens to the

Answer 30

electrons in reactions where atoms, molecules or ions are gaining or losing electrons

Question 31

Ionic equations are used to indicate what happens to ions during reactions
They help to simplify

Answer 31

complicated processes where many substances are present, but only certain ions are actually reacting with each other
For example, we can use ionic equations to show what happens when an acid neutralizes and an alkali:
HCl + NaOH → NaCl + H2O

Written out as an ionic equation would be
H+ + OH- → H2O

This is because sodium and chloride ions were present at the beginning and also at the end of the reaction, so they are unchanged
Ions which are present but do not take part in reactions are called spectator ions

Question 32

Mixtures can contain elements and

Answer 32

/ or compounds

Question 33

Each constituent of the mixture retains its

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chemical properties

Question 34

4The parts of a mixture are not chemically bonded together and so they can be separated by

Answer 34

physical means

The choice of the method of separation depends on the nature of the substances being separated
All methods rely on there being a difference in a physical property such as the boiling point or solubility, between the substances being separated

Question 35

Filtration
Used to separate an

Answer 35

undissolved solid from a mixture of the solid and a liquid / solution ( e.g., sand from a mixture of sand and water)
Centrifugation and decanting can also be used for this mixture

A piece of filter paper is placed in a filter funnel above a beaker
A mixture of insoluble solid and liquid is poured into the filter funnel
The filter paper will only allow small liquid particles to pass through as filtrate
Solid particles are too large to pass through the filter paper so will stay behind as a residue

Question 36

Crystallisation
Used to separate a

Answer 36

dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold (e.g., copper sulphate from a solution of copper (II) sulphate in water)

To test if the solution is saturated a clean, dry, cold glass rod is dipped into the solution
If the solution is saturated, crystals will form on the glass rod
The saturated solution is then allowed to cool slowly
Crystals begin to grow as solids come out of solution due to decreasing solubility
The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry

Question 37

Simple Distillation
This is used to separate a

Answer 37

a liquid and soluble solid from a solution (e.g., water from a solution of salt water) or a pure liquid from a mixture of liquids
The solution is heated and a liquid evaporates producing a vapour which rises through the neck of the round-bottomed flask (e.g. for saltwater, this would be water boiling at 100 oC)
The vapour passes through the condenser, where it cools and condenses, turning into the pure liquid that is collected in a beaker
After all the liquid is evaporated from the solution, only the solid solute will be left behind

Question 38

Fractional Distillation
This is used to separate two or more liquids that are

Answer 38

miscible with one another (e.g., ethanol and water from a mixture of the two)
The solution is heated to the temperature of the substance with the lowest boiling point
This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture
For water and ethanol
Ethanol has a boiling point of 78 ºC and water of 100 ºC
The mixture is heated until it reaches 78 ºC, at which point the ethanol boils and distills out of the mixture and condenses into the beaker
When the temperature starts to increase to 100 ºC heating should be stopped. Water and ethanol are now separated

Question 39

Paper Chromatography
This technique is used to separate substances that have

Answer 39

different solubilities in a given solvent (e.g., different coloured inks that have been mixed to make black ink)

Question 40

A pencil line is drawn on chromatography paper and spots of the

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sample are placed on it. Pencil is used for this as ink would run into the chromatogram along with the samples4

Question 41

The paper is then lowered into the solvent container, making sure that the pencil line sits

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above the level of the solvent, so the samples don’t wash into the solvent container

Question 42

The solvent travels up the paper by

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capillary action, taking some of the coloured substances with it

Question 43

Different substances have different solubilities so will travel at different rates, causing the substances

Answer 43

to spread apart

Those substances with higher solubility will travel further than the others
This will show the different components of the ink / dye

Question 44

If two or more substances are the same, they will produce ________ chromatogram

Answer 44

identical

Question 45

If the substance is a mixture, it will separate on the paper to show all the different components as

Answer 45

separete spots

Question 46

An impure substance will show up with more than one spot, a pure substance should only show up

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with one spot

Question 47

In 1803, John Dalton presented his atomic theory based on three key ideas:

Answer 47

Matter is made of atoms which are tiny particles that cannot be created, destroyed, or divided
Atoms of the same element are identical, and atoms of different elements are different
Different atoms combine together to form new substances

Question 48

At the time, the theory was correct but as science developed

Answer 48

some parts of Dalton’s theory were disproved

This is a fundamental feature of science: new experimental evidence may lead to a scientific model being changed or replaced

Question 49

The Plum Pudding Model
In 1897, physicist J.J. Thomson discovered the

Answer 49

electrone

Question 50

Using a cathode-ray tube

Answer 50

he conducted an experiment which identified the electron as a negatively charged subatomic particle, hence proving that atoms are divisible

Question 51

the plum pudding model deplicated

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negative electrons spread throughout soft globules of positively charged material

Question 52

Rutherford shot a beam of positively charged particles at a thin sheet of gold foil and based on the plum pudding model, expected the particles to pass through the

Answer 52

foil because the positive charge of the nucleus was thought to be evenly spread out

Question 53

The results of Rutherford’s scattering experiments

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did not support the idea that atoms were as described in the plum pudding model, so the model had to be changed

Question 54

In Rutherford’s model, the atom consists mainly of

Answer 54

empty space with the nucleus at the centre and the electrons orbiting in paths around the nucleus
This model was known as the nuclear model of the atom

Question 55

In the plum pudding model, atoms were described as being made from electrons embedded within a positive sphere, whereas in the nuclear model the nucleus is a

Answer 55

a positive structure at the centre of the atom, with negative (and much smaller) electrons ‘orbiting’ around the outside of it

Question 56

In 1913, Niels Bohr further developed the nuclear model by proposing that electrons

Answer 56

orbit the nucleus in fixed shells or orbitals located at set distances from the nucleus

Question 57

Each orbital has a different energy associated with it, with the higher energy orbitals being located

Answer 57

further away from the nucleus

Question 58

The Bohr Model solved the question of why the atom does not collapse inwards due to the

Answer 58

attraction between the positive nucleus and negative electrons circling the nucleus

Question 59

the subatomic particles that make up atoms

Answer 59

Protons, neutrons and electrons

Question 60

Atoms are extremely small with a radius of about

Answer 60

1 x 10-10 metres or 0.1 nanometres

Question 61

Electrons have a much smaller mass than

Answer 61

protons and neutrons (1 proton has the same mass of around 1840 electrons) and move in the space outside the nucleus in orbits

Question 62

Electrons can be

Answer 62

lost, gained, or shared during chemical processes but the proton number of an atom does not change in a chemical reaction

Question 63

Isotopes are atoms of the

Answer 63

same element that contain the same number of protons and electrons but a different number of neutrons

Question 64

Isotopes display the same

Answer 64

chemical characteristics

This is because they have the same number of electrons in their outer shells, and this is what determines their chemistry

Question 65

The difference between isotopes is

Answer 65

the neutrons which are neutral particles within the nucleus and add mass only