The periodic table is a way of organizing known elements into groups with
similar properties. Mendelev was a Russian scientist who was first to
recognise that elements can be grouped together according to atomic mass.
The modern periodic table has elements arranged in order of electronic
configuration. The table is divided into groups(columns) and periods(rows). Elements in the same group display similar chemical properties and trends emerge as we go along a period and down a group.
Click to see how size of atoms changes across a period and down a group.
Look at the electronic configuration of each atom. Can you explain the trend in atomic radius?
All elements in a particular group share similar properties. Elements in group 1 are very reactive metals, with the exception of hydrogen
gas. These metals react readily with water to produce hydrogen gas. View the videos below
Sodium reacts slowly with water to produce hydrogen gas. Hydrogen gas builds up and ignites.
Potassium reacts faster than sodium to produce hydrogen gas.
Cesium reacts more violently with water
Elements in group 2 also react with water to form hydrogen gas but are not as reactive as group 1 elements.