Answer:
The reason for covering the container is to make sure that the atmosphere in the beaker is saturated with solvent vapour. Saturating the atmosphere in the beaker with vapour stops the solvent from evaporating as it rises up the paper.
Due to it's electronic configuration w/c is 1s2 2s2 2ps 3s1 considering the last w/c is 3s1, sodium should be in row 3 period a1.