The periodic table

Chemistry

The periodic table

- The periodic table is a list of all the elements, in order of increasing atomic number.
- The columns are called groups, and numbered to 0 to 7
- The rows arecalled periods, they are numbered to 1 to 7
- There are metals and non-metals. Inside that there are: alkali metals, the halogens, the noble gases and the transition metals

More about the groups- The group number tells you how many electrons there are in the outer shell of atoms
- The outer shell electron is also called valency electrons. And their number dictates how the elements behave.- So all the elements in a group have similar properties.
- The atoms of Group 0 (noble gases) have a full outer shell. This makes them unreactive.
- Some of the Groups have special names:
Group1: Alkali metals
Group 2: Alkali earth metals
Group 7: Halogens
Group 0: Noble gases

More about the periods
- The period number tells you how many electron shells the atom has.
(The shellstructure gets ore complex from period 4 onwards)

Trends in the Periodic Table
The elements in each numbered group show trends in their properties. For example as you go down Group 1, the elementsbecome more reactive. As you go down Group 7, they become less reactive.

Halogens
• Group 7 à 7 electrons in the outer shell
• Non-metal
• Trends: Size-mass Density Reactivity
•Bonding à Covalent à Metals (Especially with Group 1 metals)
à Ionic à Non-metals
• à F
à Cl Form diatomic molecules
à Br F2; Cl2; Br2; I2à I
• Physical Properties
- Brittle
- Form coloured gases
- Poisonous
- Don’t conduct electricity

• They have similar properties because their atoms have the same number of valency(outer shell) electrons: 7
• They are so reactive because their atoms are only one electron short of a full outer shell.

Noble Gases
• Group 0 à Full outer shell à Seldom React
• Non-metal
•...