C3 Revision Answers

1: The Periodic Table

Why is it called the ‘Periodic Table’?
Similar properties occur at regular intervals

How did John Newlands order the periodic table and what did he find?
Atomic weights – found similar properties among every eighth element

How many elements were known at this time?
63

Why did ordering in atomic weights have problems?
Some elements were in the wrong group

What did Dimitri Mendeleev discover?
Some elements were yet to be discovered

What did he do?
Leave gaps to allow for their discovery

When were sub-atomic particles discovered?
Early 20^th Century

What happened after these we discovered?
The table was arranged in order of atomic numbers

How are elements arranged in the periodic table?
Periods (rows) according to number of electrons in the outer energy level. Elements with the same number of electrons are in the same group (column)

Name 3 features of the Alkali Metals
Low melting and boiling points which decrease, low density and become more reactive as you go down the group

Why are Alkali Metals stored under oil?
Because they react very vigorously with oxygen and water

What happens when a metal hydroxide is dissolved in water?
An Alkaline solution is produced

What do alkali metals react with to form ionic compounds?
Non-Metals

What are the products formed from the above reaction?
White solids that dissolve in water to form colourless solutions

What are the 5 elements in group 7 called?
Halogens

Name 4 properties of the halogens
Melting and boiling points increase as you go down the group, coloured vapours, exist as molecules made up of pairs of atoms, become less reactive as you go down the group

Why do halogens have similar properties?
All have the same number of electrons in outer energy level?

Why do they become less reactive?
Outer energy level gets further away from the nucleus so electrons are gained less easily

What do halogens react with to make ionic salts?
Metals

What will a more reactive halogen do to a less reactive one?
Displace it

Name 3 properties of transition metals
Form colourless compounds have ions with different charges and can be used as catalysts

What is the difference between transition and group 1 metals?
Higher densities in transition and are harder and more mechanically strong

2: Water

What does water naturally contain?
Microorganisms and dissolved salts

How is good quality water produced?
Water is passed through a filter bed – remove solid particles
Chlorine gas is added – kill harmful microorganisms
Fluoride is added – reduce tooth decay

How do you improve the taste and quality of tap water?
Pass the water through a filter containing carbon, silver and ion exchange resins

How do you produce pure water?
Distil it by boiling it to produce steam then condense by cooling

What is the disadvantage of this process?
Uses lots of energy which makes it expensive

What determines whether it is hard or soft water?
Amount of compounds

Why does soft water form…