2. 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 3

Define a mixture [1]

Answer 3

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

Question 4

Describe general physical properties of metals [4]

Answer 4

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

Question 5

Describe the structure of an atom [2]

Answer 5

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

Question 6

Describe the relative charge and mass of protons [2]

Answer 6

Relative charge = +1, relative mass = 1

Question 7

Describe the relative charge and mass of neutrons [2]

Answer 7

Relative charge = 0, relative mass = 1

Question 8

Describe the relative charge and mass of electrons [2]

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

They have a full outer shell of electrons

Question 11

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

Answer 11

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

Question 12

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

Answer 12

The row number = the number of occupied electron shells

Question 13

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

Answer 13

The number of protons in an atom

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

Define an isotope [2]

Answer 16

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

Question 17

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

Answer 17

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

Question 18

Describe how metal atoms form ions [2]

Answer 18

Metals lose electrons to form positive ions

Question 19

Describe how non-metal atoms form ions [2]

Answer 19

Non-metals gain electrons to form negative ions

Question 20

Describe a ionic bond [2]

Answer 20

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

Question 21

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

Answer 21

Giant ionic lattice

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 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 30

Describe the structure of diamond [3]

Answer 30

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

Question 31

Describe the structure of graphite [4]

Answer 31

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

Question 32

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

Answer 32

Giant structure, one silicon atom for every two oxygen atoms

Question 33

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

Answer 33

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

Question 34

Explain why graphite is able to conduct electricity [3]

Answer 34

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

Question 35

Explain why graphite is slippery [2]

Answer 35

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

Question 36

What is graphite used for? [2]

Answer 36

A lubricant and a conductor

Question 37

What is diamond used for? [1]

Answer 37

Cutting tools

Question 38

Describe metallic bonding [3]

Answer 38

Electrostatic force of attraction between positive metal ions in a ‘sea’ of delocalised electrons

Question 39

Describe and explain the conductivity of metals [4]

Answer 39

High conductivity / delocalised electrons / can move / carry charge (transfer energy) through the structure

Question 40

Describe and explain the malleability of metals [2]

Answer 40

High malleability (can be bent / hammered into shape) / the layers can slide off each other

Question 41

Describe and explain the melting / boiling point of metals [2]

Answer 41

High melting / boiling point / strong electrostatic force of attraction between positive metal ions and delocalised electrons