What was the issue with Newlands Ordering elements strictly according to atomic mass?
Ordering elements strictly according to atomic mass meant Newlands was forced to put some elements into groups which did not match their chemical properties.
Why was Mendeleev's periodic table more successful than Newlands'?
His method of arranging elements meant there were gaps in, which he thought meant that the elements which belonged in the gaps had not yet been discovered.
Why are group 1 metals called alkali metals?
Group 1 elements form alkaline solutions when they react with water, which is why they are called alkali metals.
Give 2 reasons why the reactivity of Group 1 elements increases as you go down the group:
The outer electron gets further from the nucleus as you go down the group.
The attraction between the nucleus and outer electron gets weaker as you go down the group - so the electron is more easily lost.
Why are group 7 metals called 'halogens' or 'salt formers'?
Group 7 elements form salts when they react with metals.
What happens the colour of 'halogens' as you go down the group?
The halogens become darker as you go down the group.
What is the balanced chemical equation for:
chlorine + sodium bromide → sodium chloride + bromine
(aq) + 2NaBr(aq) → 2NaCl(aq) + Br
What makes water hard?
The presence of calcium ions and magnesium ions in the water
Why is water in some parts of the country soft?
Water in some parts of the country is soft because it has low levels of dissolved calcium and magnesium compounds.
State one way of measuring water hardness: