Why would some atoms share more than one pair of electrons?

Answer 1

Atoms are always trying to get a full valence shell (outer shell of electrons) to make themselves stable. Hydrogen and Helium only need two electrons to do this, but the other elements need eight electrons in their valence shell. Atoms try to accomplish this in the easiest way possible, using single bonds. Sometimes, though, this doesn't work. A common example of double bonding is carbon dioxide. Carbon has four electrons in its valence shell and wants to have eight. That means it wants other atoms to share four electrons with it so it can fill its shell. The two oxygen atoms that it bonds to when it becomes carbon dioxide have six electrons in their valence shell and want eight. That means they want to share two electrons each with another atom so they can have eight electrons in their valence shell and be "full". The atoms work together, sharing electrons to fill each other's valence shells, and each of the two oxygens form a double bond with carbon. The carbon atom gets two electrons from each oxygen (four total) to add to its own four to make a total of eight electrons (a full valence shell). Each oxygen gets two electrons from the carbon atom to add to its own six, making a total of eight electrons (a full valence shell). Basically, atoms share more than one pair of electrons in double or triple bonds because it's the best way for them to fill their valence shell.

Answer 2

Atoms share pairs of electrons so as to gain stability. In most cases atoms will be unstable on their own and they have to bond with others and share electrons for stability.

Answer 3

Atoms share valence electrons in covalent bonds. The sharing of the electrons allows all the atoms to complete the octet rule and have 8 valence electrons each.