Alkali Metals
Applied Science: BTEC Level 3 National Extended Diploma, topic 1.2.8
Alkali Metals
Elements found in Group 1 (found on the left-hand side of the periodic table) are referred to as the alkali metals. Their outer shell has 1 electron in it, which is usually given away in chemical reactions.
Lithium (Li)
- Lithium has the electron structure (2,1).
- Lithium is the least reactive of the alkali metals.
- Lithium burns with a crimson flame when it reacts with oxygen.
- Lithium floats on the surface of water and will release bubbles of hydrogen gas (it effervesces).
Sodium (Na)
- Sodium has the electron structure (2,8,1).
- Sodium is more reactive than lithium because its outer electron is less strongly attracted to the positively charged nucleus. This is because it is a greater distance from the positive charge of the atom's nucleus.
- The metal floats on the surface of water, which releases enough heat to melt the sodium. The sodium moves quickly across the surface of the water.
- Sodium burns with a yellow/orange flame when it reacts with oxygen.
Potassium (K)
- Potassium has the electron structure (2,8,8,1).
- Potassium is more reactive than lithium and sodium because its outer electron is least strongly attracted to the nucleus.
- The metal floats on the surface of water, and has a similar, but more vigorous, reaction compared with sodium.
- Potassium burns with a lilac flame when it reacts with oxygen.
Alkali Metals (Group 1) - Properties
All of the elements in Group 1 have 1 electron in their outer shell. These metals are very reactive because they easily lose the electron in their outer shell. They have similar properties and usually react in similar ways.
Reacting with water
- The metal floats on the surface and melts to create a metal hydroxide (e.g. lithium hydroxide).
- When they react with water, the energy released is enough to melt the metal.
Reacting with chlorine
- A metal chloride is formed (e.g. sodium chloride), which dissolves in water to give a colourless solution.
Reacting with oxygen
- Rapidly turns from silvery shiny to dull as a metal oxide (e.g. potassium oxide) is produced.
Test yourself on Alkali Metals
Why is sodium more reactive than lithium?
Which alkali metal is not very reactive, burns with a crimson flame in oxygen and has the electron structure (2,1)?
What is the collective name for the elements in Group 1 of the periodic table?
How many electrons do atoms of alkali metals have in their outer shell?
Why are alkali metals very reactive?