Bonding, Structure and Properties of Matter

Question 1

What are cations and anions?

Answer 1

Cation - positive ion
Anion - negative ion

Question 2

What is the structure of ionic compounds?

Answer 2

A giant ionic lattice with strong electrostatic forces of attraction between the oppositely charged ions in all directions.

Question 3

What are the properties of ionic compounds?

Answer 3

-high melting and boiling points because of the strong bonds between the ions which take a lot of energy to break
-can’t conduct electricity when solid because the ions are held in place
-some dissolve in water

Question 4

How do you work out the empirical formula of ionic compound from a diagram?

Answer 4

Dot and cross diagram - count how many atoms of each element
3D diagram of lattice - work out what ions are in the compound and balance the charges of the ions so that the overall charge is 0.

Question 5

How does covalent bonding work?

Answer 5

-nuclei of atoms attracted to share electrons by electrostatic forces (very strong)
-only share electrons from outer shells
-each atom makes enough covalent bonds to fill their outer shell

Question 6

Where does covalent bonding happen?

Answer 6

In compounds of non-metals (e.g. H2O) and in non-metal elements (e.g. Cl2)

Question 7

What are the different ways of drawing covalent bonds?

Answer 7

-dot and cross diagrams with electrons in the overlaps to show which atoms the electrons come from
-displayed formulas with single lines as bonds to show how they’re connected
-3D formulas to show the arrangement of the atoms

Question 8

What are the seven main examples of simple molecular substances? What are their formulas?

Answer 8

-Hydrogen (H2)
-Chlorine (Cl2)
-Oxygen (O2)
-Nitrogen (N2)
-Methane (CH4)
-Water (H2O)
-Hydrogen Chloride (HCl)

Question 9

Describe the covalent bonding of Hydrogen (H2).

Answer 9

They only form single bonds because they have one outer electron in their outer shell and only need one more.

Question 10

Describe the covalent bonding of Chlorine (Cl2).

Answer 10

They only form single bonds because they have 7 electrons in their outer shell.

Question 11

Describe the covalent bonding of Oxygen (O2)

Answer 11

They form double bonds, which are stronger because they have 6 electrons in their outer shell and need two more to complete it.

Question 12

Describe the covalent bonding of Nitrogen (N2).

Answer 12

They form triple bonds because they have 5 electrons in their outer shells and need three more to complete it.

Question 13

Describe the covalent bonding of Methane (CH4).

Answer 13

Carbon has four outer electrons, which is half an outer shell. This means it can form 4 single covalent bonds with 4 hydrogen atoms to fill it up, making methane.

Question 14

Describe the covalent bonding of water (H2O).

Answer 14

The oxygen shares a pair of electrons with two H atoms to form two single covalent bonds.

Question 15

Describe the covalent bonding of Hydrogen Chloride (HCl).

Answer 15

Both Hydrogen and Chlorine atoms only need one electron to complete their outer shell so they form one single covalent bond.

Question 16

What are the properties of simple molecular substances?

Answer 16

-usually have very strong covalent bonds
-the forces between the molecules are very weak
-very low melting and boiling points
-mostly liquids or gases at room temperatures
-as the size of the molecules increases, so do the melting and boiling points
don’t conduct electricity because they have no charge because there’s no free electrons

Question 17

What is a polymer?

Answer 17

Lots of small units linked together to form a long molecule that has repeating units. All the atoms are joined by covalent bonds

Question 18

How do you find the molecular formula of a polymer from its diagram?

Answer 18

Write down the molecular formula of the repeating unit in brackets and put an n on the outside

Question 19

What are the properties of a polymer?

Answer 19

-larger intermolecular forces than simple covalent molecules
-higher melting and boiling points
-weaker intermolecular forces than ionic bonds
-lower melting and boiling points than ionic or giant molecular compounds

Question 20

What are the properties of giant covalent structures (macrocolecules)? What are some example of them?

Answer 20

-very high melting and boiling points
-don’t conduct electricity even when molten because they don’t contain charged particles
E.g. diamond, graphite and silicon dioxide

Question 21

What is the composition of diamond?

Answer 21

Giant covalent structure made up of carbon atoms that each form 4 covalent bonds

Question 22

What are the properties of diamond?

Answer 22

-very hard
-very high melting and boiling points
-no free ions or electrons so it doesn’t conduct electricity

Question 23

What is the composition of graphite?

Answer 23

Giant covalent structure made up of carbon atoms that only form 3 covalent bonds each, resulting in sheets of atoms, arranged in hexagons. There are no bonds between the layers so they slide over each other

Question 24

What are the properties of graphite?

Answer 24

-soft and slippery (ideal lubricating material)
-high melting point
-conducts heat and electricity (each atom has one delocalised electron that can move)

Question 25

What is graphene? What are its properties?

Answer 25

-One sheet of carbon atoms (that make up graphite)
-very strong and light (can be added to materials to strengthen them without adding weight)
-conducts heat and electricity (each atom has one delocalised electron that can move)

Question 26

What are fullerenes? What are their uses?

Answer 26

-molecules of carbon shaped like tubes or hollow balls
-made up of carbon atoms arranged in hexagons (mainly), pentagons or heptagons
-can be used to cage other molecules e.g. to deliver a drug
-catalyst (huge surface area)

Question 27

What are nanotubes? What are their properties?

Answer 27

Tiny carbon cylinder formed from fullerenes
-conduct heat and electricity
-high tensile strength (stretchy)
-used in electronic or to strengthen materials without adding weight (e.g. tennis rackets)

Question 28

What is the composition of the giant structures that make up metals?

Answer 28

-electron in the outer shell is delocalised
-strong forces of electrostatic attraction between the positive metal ions and shared negative electrons, known as metallic bonding which is very strong

Question 29

What are the properties of metals?

Answer 29

-very high melting and boiling points
-conduct heat and electricity (because of the delocalised electrons)
-Malleable - can be bent, hammered or rolled) because the layers of atoms can slide over each other

Question 30

What are alloys? Why do they work the way they do?

Answer 30

-mixtures of two or more metals or a metal and another metal which are harder and more useful than pure metals
-different types of atoms are different sizes so when mixed with a metal the other atoms distort the layers, making it harder for them to slide over each other

Question 31

What are the different categories of particles and what is each of their diametres?

Answer 31

-Coarse particles (PM10) - between 2500nm (2.5 x 10^-6 m) and 10000nm (1 x 10^-5 m)
-Fine particles (PM2.5) - between 100nm (1 x 10^-7 m) and 2500nm (2.5 x 10^-6 m)
-Nano particles - between 1nm (1 x 10^-9 m) and 100nm (1 x 10^-7 m)

Question 32

What is the formula for working out surface area to volume ratio?

Answer 32

Surface area to volume ratio = surface area / volume

Question 33

What is the surface area to volume ratio of a nano particle like? What does this mean?

Answer 33

-Very high
-means its properties vary greatly depending on whether it’s a nano particle or in bulk. E.g. you’ll need less of a catalyst if its made of nano particles

Question 34

What are some of the current uses of nano particles?

Answer 34

• catalysts
  -deliver drugs accurately to specific cells (absorbed more easily by the body)
  -electrical circuits for computer chips (conduct electricity)
  -silver ones are antibacterial - added to polymer fibres to make surgical masks and wound dressings
  -cosmetics (e.g. moisturisers)

Question 35

What are some of the arguments against nano particles being used in medicine and health? Give an example

Answer 35

-not fully tested
-affect and long-term impact on the human body unknown
-products containing them should be clearly labelled
E.g. they’re used in sun creams to protect from UV rays and they work really well but its unknown whether they’re being absorbed and damaging cells