Tuesday, October 14, 2008

periodic table - groups -notes


The elements in the periodic table are arranged according ti the increasing atomic number. In the peridoic table there are eight main groups and seven periods.
The elements in the same groups have similar properties because they have the same number of electrons in their outer shell.
The group number of the elements is the same as the number of the outer electrons. 3/4 of the periodic table is filled with metals.

There are other elements called the semi metals whos hare both the properties of metals and non metals.They conduct like metals and are brittle like non-metals.

Reactions and electron arrangementsGroup 1 elements all have atoms with 1 outer electron. e.g. sodium 2,8,1All of these atoms try to lose 1 electron so all react in the same way.

They all form a positive ion and form ionic compounds. E.g. sodium Na form sodium ion Na+.Group 1 elements all react with oxygen (that is burn) to form oxides. The products like sodium oxide, are all ionic.

sodium burn

Group 0 elements all have atoms with complete outer shells e.g. helium 2, neon 2,8. None of these elements react with anything.

Name other elements in group 1 and say how they react with oxygen giving a reason. State how argon reacts with oxygen and give a reason.

Trends in group propertiesGroup 1 elements get more reactive with water as you go down the group. e.g.Lithium (gentle fizz) is less reactive than potassium (violent lilac flame).Group 7 elements get more reactive with iron as you go up the group.Iodine darkens iron when it is heated but chlorine makes iron burst into flames.


They are called alkali metals because they react with water to form strong alkali. The increase in number of shells and atomic size causes increase ub the reactivity down the group because bigger the atom, the less its attractive force towards the nucleus.

Group 1 metals have one electron in the outermost shell which is why they are called group 1.

They are less dense than group 2 metals because they have only one electron in the outermost shell and they're stored under oil to prevent them from reacting iwth oxygen and water vapour form at the atnoshpere as it is dangerous.

Reaction with water

Sodium is a strong alkali, when it reacts with water :

1) It floats and melts.
2) Hydrogen gas is produced.
3) It forms sodium hydroxide.

Sodium + water ---------------> Sodium hydroxide + hydrogen
Na + H2O ---------------------> NaOH + H2
Na + HOH -------------> NaOH + H2

Potassium when reacting with water :

1) It floats.
2) It catches fire and burns with a lilac flame.
3) It forms potassium hydroxide and hydrogen.

Potassium + water --------------------> Potassium hydroxide + hydrogen
K + H2O --------------------------------> KOH + H2
K + HOH -------------------------------> KOH + H2


Lithium forms Lithium hydroxide and hydrogen gas when reacting with water.

Li + H2O ----------------> LiOH + H2

Rubedium (Rb)

Rb + H2O -----------> Rb (OH) + H2

When rubedium reacts with water :

1) Heat is produced.
2) Explosion takes place.
3) It forms Rubedium hydroxide and hydrogen gas.

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chemistry notes / igcse-gcse- Olevel