What do all Group 1 elements have in common?

Answer 1

All the Group 1 elements are silvery-coloured metals. They are soft, and can be easily cut with a knife to expose a shiny surface which dulls on oxidation.

These elements are highly reactive metals. The reactivity increases on descending the Group from lithium to cesium. There is a closer similarity between the elements of this Group than in any other Group of the Periodic Table.

These elements are too reactive to be found free in nature. The alkali metals are so reactive they cannot be displaced by another element, so are isolated by electrolysis of their molten salts.

The alkali metals differ from other metals in several ways. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. They have low standard enthalpies of melting and vaporization. They show relatively weak metallic bonding as only one electron is available from each atom.

Alkali metals colour flames. When the element is placed in a flame the heat provides sufficient energy to promote the outermost electron to a higher energy level. On returning to ground level, energy is emitted and this energy has a wavelength in the visible region: Li red Na yellow K lilac Rb red Cs blue

The ionic radii of the alkali metals are all much smaller than the corresponding atomic radii. This is because the atom contains one electron in an s level relatively far from the nucleus in a new quantum shell, and when it is removed to form the ion the remaining electrons are in levels closer to the nucleus. In addition, the increased effective nuclear charge attracts the electrons towards the nucleus and decreases the size of the ion.

The alkali metals are strong reducing agents. The standard electrode potentials all lie between -2.7V and -3.0V, indicating a strong tendency to form cations in solution. They can reduce oxygen, chlorine, ammonia and hydrogen. The reaction with oxygen tarnishes the metals in air, so they are stored under oil. They cannot be stored under water because they react with it to produce hydrogen and alkali hydroxides:

Answer 2

All group one elements have a single valence electron, which means that they form ions by losing that electron. This event confers a +1 charge on the atom that has lost the electron. Because of the fact that these elements only need to lose a single electron to ionize, they are very reactive and are never found in their elemental state in nature.