How reactive is an atom of sodium (na) and why?

The water and sodium first combine, the sodium releases electrons — negatively charged particles — leaving the element in a positively charged state All those positive charges repel each other, tearing the sodium apart and creating more surface area for an even bigger reaction: ka-boom. 

Non metal is an element or substance that is not a metal metal is a solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivitymetalloid is an element (e.g., germanium or silicon) whose properties are intermediate between those of metals and solid nonmetals. they are electrical semiconductors.