bonding, structure and properties of matter

Question 1

What are ions?

Answer 1

They are charged particles, formed when electrons are transferred. They can be single atoms, or groups of atoms

Question 2

what groups are most likely to form cations?

Answer 2

Group 1 and 2 elements because they form positive ions as they lose electrons easily

Question 3

what groups are most likely to form anions?

Answer 3

Group 6 and 7 elements because they form negative ions as they gain electrons easily

Question 4

What is covalent bonding?

Answer 4

A chemical bond formed when two atoms share one or more pairs of electrons to achieve a full outer energy level.

Question 5

what is metallic bonding?

Answer 5

A type of chemical bonding in metals where a cloud of delocalized electrons, known as an “electron sea”, surrounds a lattice of positive metal ions, allowing for free movement of electrons and strong electrostatic attraction.

Question 6

what is ionic bonding?

Answer 6

a type of bonding where a metal and non-metal react together. The metal atom loses electrons and the non-metal gains the electrons . They are strongly attracted to each other by electrostatic forces.

Question 7

what are simple molecular substances made up of?

Answer 7

molecules containing a few atoms joined together by covalent bonds:
- hydrogen
- oxygen
- methane
- chlorine
- nitrogen
- water
- hydrogen chloride
- methane

Question 7

what do ionic compounds have?

Answer 7

• a giant ionic lattice
• the ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositely charged ions, in all directions in the lattice

Question 7

what properties do ionic compounds have?

Answer 7

• they have high melting points and high boiling points due to the many strong bonds between the ions. it takes a lot of energy to overcome this attraction
• when they are solid, the ions are held in place so the compounds cannot conduct electricity. When they melt, the ions are free to move and they’ll carry electric current
• some ionic compounds also dissolve in water. The ions separate and are all free to move in the solution, so they carry electric current

Question 8

what properties do simple molecular substances have?

Answer 8

1) substances that have covalent bonds usually have simple molecular structures.
2) the atoms within the molecules are held together by very strong covalent bonds. By contrast, the forces of attraction between these molecules are very weak
3) to melt or boil a simple molecular compound, you only need to break the intermolecular forces and not the covalent bonds. So the melting and boiling points are very low, because the molecules are easily parted from each other.
4) Most molecular substances are gases or liquids at room temperature
5) as molecules get bigger, the strength of the intermolecular forces increases, so more energy is needed to break the bonds (melting/boiling points increase)
6) molecular compounds don’t conduct electricity. this is because they are not charged so there are no free electrons

Question 9

What are polymers?

Answer 9

Polymers are long chains of repeating units. They are lots of small units that link together to form a long molecule that has repeating sections. All the atoms in a polymer are joined by strong covalent bonds.

Question 10

what are the properties of polymers?

Answer 10

The intermolecular forces between polymer molecules are larger than between the simple covalent molecules, so more energy is needed to break them. This means they are solids at room temperature. The intermolecular forces are still weaker than ionic or covalent bonds, so they usually have lower boiling points.

Question 11

What are giant covalent structures?

Answer 11

• they are made of macromolecules
  1) in giant covalent structures, all the atoms are bonded to each other by strong covalent bonds
  2) they do not contain charged particles, so they do not conduct electricity - not even when molten (excluding graphite)
  Examples you need to know are: Diamond, Graphite, Silicon dioxide

Question 12

What is the structure of diamond?

Answer 12

Each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure

Question 13

What is the structure of graphite?

Answer 13

Each carbon atom forms 3 covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised (free to move) electron

Question 14

What is the structure of silicon dioxide?

Answer 14

Also known as silica, this is what sand is made of. Each grain of sand is one giant structure of silicon and oxygen

Question 15

What is an allotrope?

Answer 15

Allotropes are different structural forms of the same element in the same physical state.

Question 16

What are the properties of diamond?

Answer 16

• it is really hard - each carbon atom forms 4 bonds
• it has a very high melting point - strong covalent bonds
• it does not conduct electricity - no free electrons or ions

Question 17

What are the properties of graphite?

Answer 17

• Soft and slippery - no bonds between layers, held together weakly so they slide
• high melting point - strong bonds to break
• conducts electricity and thermal energy - has delocalised electrons

Question 18

What is graphene?

Answer 18

Graphene is one layer of graphite. It is one atom thick and is strong + light

Question 19

What are fullerenes formed from?

Answer 19

• fullerene molecules are molecules of carbon, shaped like closed tubes or hollow balls
• they are mainly carbon atoms in hexagons but can also contain pentagons (5 carbons) or heptagons (7 carbons)
• Fullerenes are used to cage other molecules. The fullerene structure is formed around another atom or molecule
• the first fullerene discovered was the buckminsterfullerene. It forms a hollow sphere

Question 20

What are fullerenes used for?

Answer 20

• delivering drugs around the body
• industrial catalysts
• used as a lubricant
• they can form nanotubes

Question 21

Describe nanotubes and their properties:

Answer 21

• they are tiny carbon cylinders
• the ratio between length and diameter is very high
• conduct electricity and heat energy
• high tensile strength (don’t break if stretched)
• can be used in electronics or strengthen materials

Question 22

Why are alloys used instead of pure metals?

Answer 22

Alloys are a mix of 2 or more metals or a metal with an element. They are much stronger than pure metals. This is because the different elements have different sized atoms. This means that when the elements are mixed, the atoms will distort the layers, so it is harder for the layers to slide over each other.

Question 23

why do ionic compounds usually have high density?

Answer 23

Ionic compounds tend to have high densities due to the strong electrostatic attractions between the ions.

Question 24

What is the arrangement of particles in solids?

Answer 24

1) they are in fixed positions
2) particles do not move, so the solid keeps a definite shape
3) particles vibrate to pass energy along
there is a strong force of attraction

Question 25

What is the arrangement of particles in liquids?

Answer 25

1) there is a weak force of attraction
2) particles can move past each other but stick near each other
3) the liquid has a definite volume but can change shape
4) particles are constantly moving with random motion

Question 26

What is the arrangement of particles in gases?

Answer 26

1) there is a very little force of attraction
2) the particles move constantly with random motion
3) gases do not have a fixed shape or volume

Question 27

what are the state symbols for the different states of matter?

Answer 27

solid - s
liquid - l
gas - g
aqueous - aq

(aqueous means dissolved in water)

Question 28

What are nanoparticle diameters between?

Answer 28

coarse particles (dust) - 2500nm and 10000nm
fine particles - 100nm and 2500nm
nanoparticles - 1nm and 100nm