Topic 2: Atoms, elements and compounds

Question 1

What are elements?

Answer 1

Elements are pure substances, containing only one type of atom.
They cannot be separated.
Some exist as single atoms (e.g. helium, neon and argon)
Some exist as molecules (e.g. oxygen)

Question 2

What are compounds?

Answer 2

Compounds are substances containing different elements chemically combined.
They cannot be separated without a chemical reaction.
E.g. H2O, CO2

Question 3

What are mixtures?

Answer 3

Mixture are impure substances that contain more than one substance not chemically bonded.
They can be separated without a chemical reaction.

Question 4

What is an atom?

Answer 4

The smallest piece of an element that can exist.

Question 5

State the subatomic particles of atoms.

Answer 5

Protons
Neutrons
Electrons.

Question 6

Where are the protons located?

Answer 6

In the nucleus

Question 7

Where are the neutrons located?

Answer 7

In the nucleus

Question 8

Where are the electrons located?

Answer 8

In energy levels around the nucleus.

Question 9

State the relative mass of a proton.

Answer 9

1

Question 10

State the relative charge of a proton

Answer 10

+1

Question 11

State the relative mass of a neutron.

Answer 11

1

Question 12

State the relative charge of a neutron

Answer 12

0

Question 13

State the relative mass of an electron.

Answer 13

Negligible/Almost zero

Question 14

State the relative charge of an electron.

Answer 14

-1

Question 15

What is the proton number?

Answer 15

The number of protons/electrons

Question 16

What is the nucleon number?

Answer 16

The number of protons + neutrons.
Also known as mass number

Question 17

How many electrons can the first energy level/shell hold?

Answer 17

2 electrons.

Question 18

What does the period number tell you?

Answer 18

The number of electron shells in the atoms.

Question 19

What does the number of electrons in the outer most shell tell us?

Answer 19

Which group the atom can be found in.

Question 20

What are isotopes?

Answer 20

Atoms of an element with different numbers of neutrons but the same proton number.

Question 21

Do isotopes have the same electronic configuration?

Answer 21

Yes. This means that the reactivity also remains the same.

Question 22

How are isotopes used in medicine?

Answer 22

Tracers - to map a path through different body systems
Sterilising equipment
Diagnosing diseases (e.g. cancer)
Radiotherapy - treating cancer.

Question 23

How are isotopes used in industry?

Answer 23

Tracers - to find out what is happening inside an object without opening it.
Somke alarms
Dating rocks (carbon dating)
Nuclear power stations

Question 24

What are the two types of isotopes.

Answer 24

Radioactive
Non-radioactive

Question 25

What are radioactive isotopes?

Answer 25

An isotope with an unstable nucleus.

Question 26

Write the formula to find the relative atomic mass of an element.

Answer 26

Question 27

How are ions formed?

Answer 27

When an atom loses or gains electrons from their outermost electron shell.

Question 28

What are metal ions?

Answer 28

Cations

Question 29

What are non-metal ions?

Answer 29

Anions

Question 30

Describe the structure of an ionic compound.

Answer 30

An ionic compound is a giant structure of ions. The ions have a regular, repeating arrangement called an ionic lattice. The lattice is formed because the ions attract each other and forma regular patter with oppositely charged ions next to each other.

Question 31

How are ionic compounds formed?

Answer 31

When metal atoms react with non-metal atoms. They lose their outer electrons which the non-metal atoms gain to form positive and negative ions. The positive and negative ions are held together by strong electrostatic forces of attraction between opposite charges. This force of attraction is known as an ionic bond, which hold ionic compounds together.

Question 32

State the physical properties of ionic compounds.

Answer 32

1. They are hard to break due to the presence of the strong force of attraction between the positive and negative ions. 2. They are considered brittle. They generally break into pieces when pressure is applied. 3. They have high melting and boiling points 4. They are soluble in polar solvents 5. They do not conduct electricity in the solid state but only in the molten state.

Question 33

When does covalent bonding occur?

Answer 33

When two non-metal atoms share a pair of electrons

Question 34

State the properties of covalent compounds.

Answer 34

1. Low melting and boiling points because the intermolecular forces are much weaker than the strong covalent bonds in molecules. 2. Poor conductors of electricity.

Question 35

State the properties of giant covalent structures.

Answer 35

1. Extremely strong as they contain many bonds. 2. Arranged into giant regular lattices.

Question 36

Name the allotropes of carbon

Answer 36

Graphite Diamond

Question 37

State the uses of graphite.

Answer 37

stationary lubricants industries nuclear reactors

Question 38

State the uses of diamonds.

Answer 38

Jewelery making construction minor industrial applications surgeries cutting tools.

Question 39

State the properties of graphite.

Answer 39

Question 40

State the properties of diamond

Answer 40

Question 41

State the properties of silicon (IV) dioxide.

Answer 41