Week 9

Question 1

What is an ion

Answer 1

If protons don’t equal the amount of electrons then the atom is charged

Question 2

Isotopes

Answer 2

If the number of neutrons vary then it’s an isotope

Question 3

Periodic table

Answer 3

Elements are arranged in their increasing atomic number (z) / proton number

Question 4

How to get atomic weight

Answer 4

Times the protons by the elements abundance in the atmosphere E.G

12 x 0.989 = 11.868
13 x 0.011 = 0.143
11.868 + 0.143 = 12.011 = carbons atomic weight

Question 5

Ions

Answer 5

If electrons are gained or lost atoms become charged
+ve = cations
-ve = anions

Question 6

Ionic Compounds

Answer 6

When a non-metal reacts with a metal electron transfer occurs. Electrostatic attraction between +ve and -ve happens E.g. Na+ and Cl- = NaCl

Charges balance to produce a neutral compound E.g Ca2+ and 2Cl- = CaCl2

They tend to have high melting points and conduct electricity when a liquid

Question 7

Molecular compounds

Answer 7

Covalent compounds - atoms share electrons
Interactions within a molecule are strong but interactions between molecules are weak and they have low melting and boiling points

Question 8

Empirical formula

Answer 8

Gives elements the smallest possible ratio, usually used for ionic compounds
To obtain this divide the molecular formula by its lowest denominator
E.g. C2H6 ethane = CH3
Divided by 2

Question 9

Single and double bonds

Answer 9

If 2 electrons are shared between a pair of atoms it’s a single bond
If 4 electrons are shared it’s a double bond
Double bonds are stronger and short than single bonds
Single bonds can rotate whereas double bonds and even triple bonds can’t

Question 10

Isomers

Answer 10

Different molecules that have the same formula but different connectivity
Gives them different reactivity and properties

Structural isomers
Cis/trans isomers

Question 11

Molecular shape

Answer 11

Molecules have a 3D shape
Tetrahedral methane:
Carbon at the centre of tetrahedron
Hydrogen at vertices

Different from square planar:
Nickel at centre of square
CO at vertices of square
Planar

Octahedral:
SF6
S in the centre of the octahedron
F at the vertices

Planar:
Flat
All the atoms are in the same space
E.g. Benzene

Question 12

Sterics and electronics

Answer 12

Molecular shape is a product of steric and electronic effects

Sterics:
Atoms occupy space
Atoms bonded to the same central atom will want to be as far away as possible

Electronics:
Electrons interact with each other - like charges repel
Lots of electrons can interact in lots of different ways - each will have a different energy