Group 1, Group 7 and Group 0

Group 1 Metals

The alkali metals, found in group 1 of the periodic table, are highly reactive metals with one electron in their outer shell. They have similar properties, such as being shiny and good conductors of electricity. Group 1 metals typically have lower melting and boiling points than other metals.

These are the trends of the group 1 metals as you move down the group:

  • Melting and boiling points decrease
  • Relative atomic mass increases
  • Reactivity increases

Reactions with water

Group 1 metals react with water to produce hydrogen gas and a metal hydroxide. The general equation for this is:

Metal + WaterMetal hydroxide + Hydrogen

For example, lithium reacts with water to form lithium hydroxide and hydrogen:

Lithium + Water → Lithium hydroxide + Hydrogen

2Li + 2H2O2LiOH + H2

Reactions with halogens

Group 1 metals react with halogens to produce a salt and the general equation for this is:

Metal + HalogenSalt

For example, the reaction between the alkali metal, sodium, and the halogen, chlorine, forms sodium chloride.

Sodium + Chlorine → Sodium chloride

2Na + Cl22NaCl

Reactions with oxygen

Group 1 metals react with oxygen to form oxides and the general equation for this is:

Metal + OxygenMetal oxide

An example of this is the reaction between sodium and oxygen to form sodium oxide:

Sodium + Oxygen → Sodium Oxide

4Na + O22Na2O

Group 7

The elements in group 7 of the periodic table are called halogens. They are all non-metals and have similar properties. The table below shows the properties of the first five halogens at room temperature.

HalogenColourState
FluorineYellowGas
ChlorineGreenGas
BromineRed-brownLiquid
IodinePurple/blackSolid

These are the trends of the halogens as you go down the group:

  • Melting and boiling points increase
  • Relative atomic mass increases
  • Reactivity decreases
  • Colour becomes darker

Displacement reactions

Halogens are involved in displacement reactions, in which a more reactive halogen replaces a less reactive halogen. For example, fluorine reacts with sodium chloride to form sodium fluoride and chlorine:

Fluorine + Sodium chloride → Sodium fluoride + Chlorine

As fluorine is higher than chlorine on the periodic table, it is more reactive. This means that fluorine displaces chlorine. Another example is:

Chlorine + Sodium bromide → Sodium chloride + Bromine

As chlorine is more reactive than bromine, it replaces bromine.

Group 0

Group 0, also known as the noble gases, have a full outer shell of electrons, making them stable and unreactive. Helium has 2 electrons in its outer shell, while the other noble gases have 8. Under normal conditions, all noble gases are colourless, odourless and tasteless.

When transporting reactive substances, it is important to avoid exposing them to air. This is because they may react with the oxygen present in the atmosphere. To prevent this, a common practice is to package the substance with a noble gas, as these gases will not react with the substance being transported.

These are the trends of group 0 elements as you go down the group:

  • Melting and boiling point increase
  • Relative atomic mass increases