Complete the following passage choosing the terms among those listed below. There are three extra words, which you do not need to use.

Alkali are in group I of the periodic table.
They have electron in their shell.
Alkali metals are enough, so they can be cut and then they are and silvery.
They are conductors. They have melting points.
They become reactive down the group. The force of attraction between the nucleus and the single outer electron is .
They reacts with to form oxides.