C3 - Atoms, elements and compounds

Question 1

Define an element [1]

Answer 1

Made of one type of atom

Question 2

Define a compound [1]

Answer 2

Made of more than one type of atom chemically bonded together

Question 2

Describe general physical properties of metals [4]

Answer 2

High melting and boiling points, mallleable, ductile, good conductors of heat and electricity

Question 2

Define a mixture [1]

Answer 2

Two or more elements / compounds mixed together that can be separated by physical means

Question 2

What is the difference between a physical change and chemical change? [2]

Answer 2

Physical changes involve a change in state / separation of a mixture. Chemical changes involve atleast one new substance being made

Question 3

What does the symbol ⇌ mean? [1]

Answer 3

Reversible reaction

Question 4

What is the difference in colour between the anhydrous and hydrated forms of copper (II) sulphate? [2]

Answer 4

Anhydrous copper sulphate = white, hydrated copper sulphate = blue

Question 5

What is the difference in colour between the anhydrous and hydrated forms of cobalt (II) chloride? [2]

Answer 5

Anhydrous cobalt chloride = blue, hydrated cobalt chloride = pink

Question 6

Describe the structure of an atom [2]

Answer 6

Central nucleus containing protons and neutrons, ‘shells’ of electrons

Question 7

Describe the relative charge and mass of protons [2]

Answer 7

Relative charge = +1, relative mass = 1

Question 8

Describe the relative charge and mass of neutrons [2]

Answer 8

Relative charge = 0, relative mass = 1

Question 9

Describe the relative charge and mass of electrons [2]

Answer 9

Relative charge = -1, relative mass = 1/2000

Question 10

Describe the maximum number of electrons that can fit on the first 3 shells [1]

Answer 10

1st shell = 2 electrons, 2nd shell = 8 electrons, 3rd shell = 8 electrons

Question 11

Why are elements in group 0 (the noble gases) unreactive? [1]

Answer 11

They have a full outer shell of electrons

Question 12

How is group number in the periodic table related to electronic structure? [1]

Answer 12

The group number = the number of electrons in the outer shell

Question 13

How is period (row) number in the periodic table related to electronic structure? [1]

Answer 13

The row number = the number of occupied electron shells

Question 14

What is the atomic number of an element? [1]

Answer 14

The number of protons in an atom

Question 15

What is the mass number or an element? [1]

Answer 15

The number of nucleons (protons + neutrons) in an atom

Question 16

How are elements arranged in the periodic table? [2]

Answer 16

In ascending atomic number, elements with similar properties arranged in groups

Question 17

Define an isotope [2]

Answer 17

Atoms of the same element with the same number of protons and electrons but a different number of neutrons

Question 18

Why do isotopes have the same chemical properties? [1]

Answer 18

Because they have the same number of electrons in their outer shell

Question 19

Describe how metal atoms form ions [2]

Answer 19

Metals lose electrons to form positive ions

Question 20

Describe how non-metal atoms form ions [2]

Answer 20

Non-metals gain electrons to form negative ions

Question 21

Describe a ionic bond [2]

Answer 21

The electrostatic attraction between positive metal ions and negative non-metal ions

Question 22

Describe the properties of ionic substances [4]

Answer 22

Low volatility, high solubility, high melting and boiling point, conducts when molten or aqueous

Question 22

What type of structure do ionic substances form? [1]

Answer 22

Giant ionic lattice

Question 23

Explain the high melting / boiling point of ionic substances [2]

Answer 23

High melting point because of strong electrostatic force of attraction between ions that requires a lot of energy to overcome

Question 24

Explain the electrical conductivity of ionic substances [2]

Answer 24

Able to conduct when molten or aqueous because the ions are free to move and carry charge

Question 25

Describe a covalent bond [1]

Answer 25

A shared pair of electrons between non-metal atoms

Question 26

Describe the properties of covalent substances [4]

Answer 26

High volatility, low solubility, low melting and boiling point, does not conduct electricity

Question 27

Explain the low melting / boiling point of covalent substances [2]

Answer 27

Weak intermolecular forces that require a small amount of energy to overcome

Question 28

Explain why simple covalent substances don’t conduct electricity [2]

Answer 28

No free mobile charge carriers (electrons or ions) to carry charge through the structure

Question 29

Name three (covalent) macromolecules [3]

Answer 29

Diamond, graphite, silicon (IV) oxide (silica / silicon dioxide)

Question 29

Describe the structure of diamond [3]

Answer 29

Giant structure, made of carbon atoms, each carbon forms 4 bonds with another carbon

Question 29

Describe the structure of graphite [4]

Answer 29

Giant structure, made of carbon atoms, each carbon forms 3 bonds with another carbon, layered structure

Question 30

Explain why diamond, graphite and silica have a high melting / boiling point [2]

Answer 30

Lots of strong covalent bonds that require a lot of energy to overcome

Question 30

Describe the structure of silicon (IV) oxide [2]

Answer 30

Giant structure, one silicon atom for every two oxygen atoms

Question 31

Explain why graphite is able to conduct electricity [3]

Answer 31

Carbon atoms only form 3 bonds so one valence electron is free and delocalised and can carry charge through the structure

Question 32

Explain why graphite is slippery [2]

Answer 32

Weak intermolecular forces between layers so the layers can slide off each other

Question 33

What is graphite used for? [2]

Answer 33

A lubricant and a conductor

Question 34

What is diamond used for? [1]

Answer 34

Cutting tools