The number of electrons in an atom's outermost valence shell governs its bonding behavior.
In N₂, three electrons are being shared by each nitrogen atom, making a total of 6 shared electrons.
In CCl₄, 4 electrons are being shared by each carbon atom and 1 electron is being shared by each chlorine atom
In SiO₂, 4 electrons are being shared by each silicon atom and 2 electrons are being shared by each oxygen atom.
In AlCl₃, 3 electrons are being shared by each aluminum atom and 1 electron is being shared by each Cl atom
In CaCl₂, 2 electrons are lost by the calcium atom and 1 electron is gained by each chlorine atom
In LiBr, 1 electron is lost by the lithium atom and 1 electron is gained by the bromine atom