What is a measure of how closely packed particles of matter are in q certain amount of space

Idon’t understand this page, can someone ?

Acompound contains c, h, and o atoms. when 1.130 g of the compound is burned in oxygen, 1.064 g co2 and 0.3631 g h2o are produced. what is the empirical formula of this compound?

Which element would mostly likely have an electron affinity measuring closest to zero