C2.1/2 - Structure and Bonding

Question 1

What is a compound?

Answer 1

Compounds are substances in which atoms of two or more elements are chemically combined.

Question 2

Why do atoms take part in chemical bonding?

Answer 2

Atoms take part in chemical bonding in order to achieve the electronic structure of a noble gas (full outer energy level).

Question 3

When an atom loses an electron, what charge does the remaining ion have?

Answer 3

When an atom loses an electron, the remaining ion has a positive charge.

Question 4

When an atom gains an electron, what charge does the remaining ion have?

Answer 4

When an atom gains an electron, the remaining ion has a negative charge.

Question 5

What is the electronic structure of an ion?

Answer 5

Ions have the electronic structure of a noble gas (Group 0).

Question 6

What do we call the elements in Group 1?

Answer 6

The elements in Group 1 are called the Alkali metals.

Question 7

When Group 1 metals react with non-metal elements, what type of ion is formed?

Answer 7

When Group 1 metals react with non-metal elements, the Group 1 element forms an in with a single positive charge.

Question 8

What do we call the elements in Group 7?

Answer 8

The elements in Group 7 are called the Halogens.

Question 9

When Group 7 elements react with the alkali metals, what charge does the halide ion gain?

Answer 9

When Group 7 elements react with alkali metals, the halide ion has a negative charge.

Question 10

What type of bonding happens when atoms share pairs of electrons?

Answer 10

When atoms share pairs of electrons, this is called covalent bonding.

Question 11

What do we call covalent molecules with only a small number of atoms, such as H2, Cl2, O2, HCl, H20, NH3 and CH4?

Answer 11

Covalent molecules with only a small number of atoms are called simple molecules.

Question 12

What are the melting and boiling points of simple molecules and why?

Answer 12

Simple molecules have low melting and boiling points due to the weak intermolecular forces between the molecules.

Question 13

Why do simple molecules not conduct electricity?

Answer 13

Simple molecules do not conduct electricity as the molecules do not have an overall electric charge.

Question 14

Why do ionic compounds have high melting and boiling points?

Answer 14

Ionic compounds have high melting and boiling points as there are strong electrostatic forces between oppositely charged ions.

Question 15

Why do solid ionic compounds not conduct electricity?

Answer 15

Solid ionic compounds cannot conduct electricity because the ions are not free to move.

Question 16

Why do ionic compounds conduct electricity when they are melted or dissolved in water?

Answer 16

Ionic compounds can conduct electricity when melted or dissolved in water because now the ions are free to move.

Question 17

What type of molecules are diamond, graphite and silicon dioxide?

Answer 17

Diamond, graphite, and silicon dioxide are giant covalent lattices (macromolecules).

Question 18

Why do giant covalent structures have very high melting points?

Answer 18

Giant covalent structures have very high melting points as all the atoms are linked to other atoms by strong covalent bonds.

Question 19

Diamond and graphite are formed from which element?

Answer 19

Diamond and graphite are formed from carbon.

Question 20

What is the structure of silicon dioxide?

Answer 20

Each silicon atom is covalently bonded to four oxygen atoms.

Each oxygen atom is covalently bonded to two silicon atoms.

Question 21

What is the structure of diamond?

Answer 21

Each carbon atom forms four covalent bonds.

Question 22

What is the structure of graphite?

Answer 22

Each carbon atom forms three covalent bonds.

Question 23

Why is diamond very hard?

Answer 23

Diamond is very hard because each carbon atom forms four strong covalent bonds.

Question 24

Why is graphite soft and slippery?

Answer 24

Graphite is soft and slippery because it consists of layers.

There are no covalent bonds/weak intermolecular forces between the layers so they are free to slide.

Question 25

Why is graphite a good conductor of heat and electricity?

Answer 25

In graphite, one electron from each carbon atom is delocalised. The free electrons allow graphite to conduct heat and electricity as they can move and carry energy.

Question 26

What is the structure of fullerenes?

Answer 26

Fullerenes consist of hexagonal rings of carbon atoms.

Question 27

What are fullerenes used in?

Answer 27

Fullerenes have uses such as lubricants and in nanotubes.

Question 28

Why are metals good conductors of heat and electricity?

Answer 28

Metals are good conductors of heat and electricity because they have delocalised electrons that can move.

Question 29

Why can metals be bent and shaped?

Answer 29

Metals can be bent and shaped because the layers of atoms in metals are able to slide over each other. The atoms are of the same size.

Question 30

What are alloys?

Answer 30

Alloys are usually made from two or more metals or other elements joined to metals to make them stronger.

Question 31

Why are alloys harder than pure metals?

Answer 31

Alloys are harder than pure metals because the different sized atoms distort the layers so it is difficult for them to slide over each other.

Question 32

What are shape memory alloys?

Answer 32

Shape memory alloys can return to their original shape after being deformed, usually by heating (nitinol/dental braces)

Question 33

What conditions can we change to alter the properties of a polymer?

Answer 33

To alter the properties of a polymer, we can change the temperature of the reaction or use a different catalyst (to produce high-density poly(ethene) or low-density poly(ethene).

Question 34

What is a thermosoftening polymer?

Answer 34

Thermosoftening polymers consist of individual tanlged polymer chains. When we heat them, these polymers melt and can be reshaped.

Question 35

What is meant by a thermosetting polymer?

Answer 35

Thermosetting polymersconsist of polymer chains with covalent cross-links between them. They do not melt when they are heated.

Question 36

In terms of intermolecular forces, why can thermosoftening polymers melt when heated?

Answer 36

Thermosoftening polymers have weak intermolecular forces between the chains. They are easily broken, hence the polymer can melt easily.

Question 37

What are nanoparticles?

Answer 37

Nanoparticles are between 1-100nm in size. They consist of a few hundred atoms.

Question 38

Why are nanoparticles useful?

Answer 38

Nanoparticles are useful because they have a high surface area to volume ratio.