Chemistry

Newlands tried to arrange the periodic table in 1864, when only 63 elements were known. He arranged them according to their atomic weights, and found similar properties in every 8th element in the series. These elements are now known as the Noble Gases, Group 8 on the periodic table.

Mendeleev realised that some elements had not been discovered, and left gaps in his version of the table in 1869. He used his table to predict the properties of elements which had not been discovered yet.

The 6 elements in group 1 are Lithium, Sodium, Potassium, Rubidium, Caesium and Francium. They all have one electron in their outer shell, meaning that they are very reactive. Their properties are:

low melting and boiling points (which decrease as you move down the group)

low density (lithium, sodium and potassium are all less dense than water)

very reactive (reactivity increases as you move down the group)

elements get softer as you move down the group

They are reactive because they want to lose the electron in their outer shell to make them more stable. The further the electron is from the nucleus, the more reactive it becomes, and the more easier it is to lose.

They are stored in oil because they react vigorously with both oxygen and water. When they react with water, a metal hydroxide is formed and hydrogen is given off. If a metal hydroxide is dissolved in water, an alkaline solution is made. Alkali metals fom ionic compounds when they react with non metals. When this happens, the metal atom loses/donates one electron to another atom. The metal ion created will have a positive charge (+1). The products are white solids which dissolve in water to create colourless solutions.