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The Group 1 elements are called the alkali metals. They are placed in the vertical column on the left-hand side of the periodic table.

All the Group 1 elements are very reactive. They must be stored under oil to keep air and water away from them. When they react with water, Group 1 elements form metal hydroxides which are alkaline (with a pH above 7). This is why they are called alkali metals. These metals also have unusual physical properties for metals:

• they have low melting points (increasing up the group from 28°C for Cs to 180°C for Li, whereas typical metals have much higher melting points, such as iron which melts at 1,540°C)
• they are very soft and so can easily be cut with a knife
• they have low densities (Li, Na and K float on water and so must have a density that is less than 1 g/cm³)