Cations and Anions

A Cation is formed after an Atom loses one or more electrons, gaining a positive charge.

An Anion is formed after an Atom gains one or more electrons, gaining a negetive charge

The two elements that bond in an Ionic bond are metals and nonmetals, transferring valence electrons between them.

You can find what the Ionic charge of an element will be by looking at the group number of the element, an Ion formed by metal is equal to the group number of that metal.

Two examples of an Ionic bond are NaCl (Sodium Chloride) and LiF (Lithium Flouride). each of these bonds are transferring electrons between each atom in the bond. 

COvalent bonding 

Only nonmetals will bond in a covalent bond, and as they share their electrons with each other. In a covalent bond, electrons are shared equally between themselves.

In a polar covalent bond, the electrons are unequally shared, in a covalent bond, the electrons are shared equally.

Electronegativity is a way to describe the strength that specific atoms attract electrons. the weaker the electronegativity level, the stronger the flow of electrons, which, is conductivity, the flow of electrons through a surface.

Two examples of this are H2O (water) and C12H22O11 (sugar) which are both covalent bonds that share electrons.

Valence electrons

The reason that atoms tend to favor losing or gaining electrons is because atoms are most stable at either zero or 8 valence electrons, so any atoms with 4 or fewer valence electrons will favor losing electrons and any atoms with 5 or more will favor gaining electrons to become stable.

For example, hydrogen will favor losing its single valence electron to become zero, while fluorine will prefer to take that single electron from hydrogen to get 8 electrons.