Moving from left to right across a A row of elements in the periodic table., the A substance made of one type of atom only. become less metallic. This is related to the increase in the number of Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. in the outer shell of their All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons.. The atoms become more likely to gain or share electrons, rather than lose them when they form A substance formed by the chemical union of two or more elements..
