That depends on the wave, if you're talking about sound, it makes matter move in a similar wavelength as them, a mountainous shape. Light however would make whatever matter it hits start to move in the same direction as the light's angle of approach.
Sodium because according to the atomic size trend of the periodic table. Elements further to the left are bigger while elements tot he right are smaller. This is also do to their charges, Na has a +1 charge meaning it doesn’t pull the electrons as close as the Mg does with its +2 charge.
