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Trends within the periodic table

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Elements within different groups within the periodic table have different physical and chemical properties. This determines the kinds of reactions these elements have. Different groups also show different trends, in terms of reactivity, as you move down a group. This can also determine how violently a reaction occurs - or whether it happens at all.

Group 1 Elements

The elements [element: A substance made of one type of atom only. in group 1 are called the alkali metals. They belong to the left-hand column in the periodic table. They are very reactive [reactive: The tendency of a substance to undergo chemical reaction. and must be stored in oil to avoid contact with air or water.

Periodic table with Group 1 highlighted

Periodic table Group 1

The alkali metals are soft, reactive metals. They react vigorously with water and become more reactive as you go down the group.

Common properties

The alkali metals have the following properties in common:

  • they are very soft and can be cut easily with a knife

  • they have low  [density: A measure of the quantity of some physical property (usually mass) per unit length, area, or volume (usually volume).densities (lithium, sodium and potassium will float on water)

  • they react quickly with water - producing hydroxides and hydrogen gas

  • their hydroxides dissolve in water to form alkaline solutions

In general:

group 1 metal + water → group 1 metal hydroxide + hydrogen

2M(s) + 2H2O(l) → 2MOH(aq) + H2(g)

(M stands for the symbol of a Group 1 metal)

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