Describe Newland’s contributions to the periodic table.
Ordered elements in increasing atomic mass
Noticed every 8th element had similar properties
(noble gases not been discovered yet).
Put similar properties into columns called groups.
By strictly ordering elements in order of atomic mass some elements did not match properties of the others in the group. E.g. iron put with oxygen and sulphur
Describe Mendeleev’s contributions to the periodic table.
Ordered elements in increasing atomic mass
Put similar properties into columns called groups
Element were put into groups if their properties were similar even if this meant swapping element around breaking the increasing atomic mass order.
Gaps for elements create - he thought had not been discovered
Describe the Modern Periodic table.
When electrons, protons and neutrons were discovered the periodic table was ordered in atomic (proton) number.
Elements of the same group have the same number of electrons in the outer shell
Elements of the same group have similar chemical properties.
Group 1 metal Properties & reactions
- Low density (first 3 less than water so float)
- React with non-metals to form ionic compounds and form metal ions with a +1 charge.
- Group 1 compounds are white and dissolve in water to form colourless solution.
- Reacts with water to form hydrogen and an alkaline solution:
Metal + Water → Metal hydroxide + Hydrogen
2M + 2H2O → 2MOH + H2
Where M = any group 1 metal symbol e.g. Li
Describe the trend of properties down group 1
- Lower melting and boiling point
* More reactive
Explain why reactivity increase down group 1
Because electron on the outer shell is more easily lost as you go down the group.
As you go down the group the electron is further from the nucleus (and inner shell repel the outer electron hence increased shielding).
Hence a lower electrostatic attraction between nucleus and electron.
Transition metals
• Middle large group of metals
Many transition elements have ions with different charges e.g. iron – Fe2+ and Fe3+.
- Form coloured compound
- Useful as catalysts
Transition metals compared to Group 1 metals
- Have higher melting points and densities.
- Are stronger and harder.
- Much less reactive – don’t react as vigorously with water and oxygen.
Group 7 properties
• melting point increase down the group
Colour gets darker:
(Green/yellow = chlorine)
(Brown = Bromine)
(Dark Grey = iodine)
React with metals to form ionic compounds and forms a halide ion with a charge of -1.
Explain the why the reactivity down group 7 decrease.
Less reactive -
Because electron is less easily gained to the outer shell as you go down the group.
As you go down the group electron is further from the nucleus and (and inner shell repel the outer electron hence increased shielding).
Lower electrostatic attraction between nucleus and gained electron means it harder to keep electron.
Describe the trends in Group 7 Displacement reactions
Give an example
More reactive halogen displaces less reactive halogen to form an aqueous solution of its salt
E.g.
chlorine + sodium bromide → bromine + sodium chloride
Chlorine is more reactive than bromide hence chlorine displaces the bromide.
