Sunday, March 1, 2009

igcsechemistry free -notes The periodic table

Elements are placed in order of increasing atomic number so hydrogen atomic number 1 is firsthelium atomic number 2 is second etc.


A group is a column of elements with similar properties in the periodic table. See figure1. e.g all of the following are in the same group and are silver in colour, soft and good conductors of electricity.

The position of groups in the periodic tableThe positions of the alkali metals (group 1), the halogens (group 7), the noble gases (group 0) and the transition metals are shown in figure 1 above.

Task :Label a copy of the periodic table to show a group, a period, the alkali metals, halogens, noble gases, transition metals, metals, and non-metals.

Reactions and electron arrangements

Group 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.

Group 0 elements all have atoms with complete outer shells

e.g. helium 2, neon 2,8. None of these elements react with anything.

Task - 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.

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