Question

What's the difference between a covalent compound and an ionic compound?

Which elements form each? Do they both form molecules?

Answer 1

An old chesnut….

Explanation:

An ionic compound, a salt, is a material that is conceived to be composed of positive and negative ions. Take a common salt...`NaCl(s)`. In the solid state this is composed of interpenetrating positive and negative ions. Now of course there is electrostatic repulsion between ions of like charge. And there is also electrostatic attraction between ions of unlike charge. Electrostatic attraction wins, and binds the ionic salt together in the solid state.

On the other hand, a covalent bond is a region of high electron density between two positively charged atomic nuclei. In general covalent bonds are a characteristic of MOLECULAR species, i.e. discrete molecules...such as `O_2`, `CO_2`, and `H_2O`. On the other, other hand, covalent bonding can persist non-molecularly in such species as graphite, and diamond, and silica.