Properties of the Group I Elements

  • The Group I metals are also called the alkali metals as they form alkaline solutions with high pH values when reacted with water.
  • The Group I metals are lithium, sodium, potassium, rubidium, caesium and francium.
  • They are soft metals and be easily cut with a knife.
  • They have relatively low densities and low melting points.
  • They are very reactive metals

Group 1 metals in Periodic Table, IGCSE & GCSE Chemistry revision notes

The alkali metals lie on the far left hand side of the Periodic table

Trends in Group I

  • The alkali metals are soft and easy to cut, getting softer as you move down the Group due to increasing density (except for potassium which fluctuates).
  • The first three alkali metals are less dense than water.
  • They all have relatively low melting points which decrease as you move down the Group due to decreasing electrostatic forces.

Graph MP Group 1, IGCSE & GCSE Chemistry revision notes

The melting point of the Group I metals decreases moving down the group

  • The reactivity of the Group I metals increases as you go down the group.
  • Each outer shell contains only one electron which is lost during the reaction.
  • The next shell down automatically becomes the outermost shell and since it is already full, the atom obtains noble gas configuration.
  • As you go down Group I, the number of shells of electrons increases by 1 (Period number increases down the Periodic table).
  • This means that the outer electron is further away from the nucleus so there are weaker forces of attraction between the electron and the nucleus.
  • Therefore less energy is required to overcome the forces of attraction between the negatively charged outermost electron and the positively charged nucleus.
  • This allows the electron to be lost more easily, making each alkali more reactive than the previous one as you go down the Group.

Electronic configuration of Li, Na and K, IGCSE & GCSE Chemistry revision notes

Electron shell diagrams of the first three elements in Group I

  • Rubidium, caesium and francium will thus react even more vigorously with air and water.
  • Of the alkali metals, lithium at the top of the group is the least reactive and francium which is at the bottom would be the most reactive.
  • Francium is extremely rare and radioactive so it is difficult to confirm predictions.

Trends in Group I, IGCSE & GCSE Chemistry revision notes

Reactions of the Group I Elements

  • They react readily with oxygen and water vapour in air so they are usually kept under oil to stop them from reacting.
  • They react vigorously in water to produce an alkaline metal hydroxide solution and hydrogen gas

  • All of the Group I metals react vigorously when heated with chlorine gas to form salts called metal chlorides.
  • This reaction becomes more vigorous moving down the Group as with the reaction between the metals and water.

Reactions of the Group I Elements 1, IGCSE & GCSE Chemistry revision notes

  • The metals also react with oxygen in the air forming metal oxides which is how the alkali metals tarnish when exposed to the air.
  • The metal oxide produced is a dull coating which covers the metals surface.

Reactions of the Group I Elements 2, IGCSE & GCSE Chemistry revision notes

AQA GCSE Chemistry Notes

Share with friends

Want to aim for a Level 9?

See if you’ve got what it takes. Test yourself with our topic questions.

Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.