Why are ionic compounds formed when a metal from the left side of the periodic table reacts with a nonmetal from the right side?

Answer 1

One of the ideas regarding the manner in which atoms bond to other atoms is that atoms want to achieve an electron configuration like that of an inert or noble gas. That is, atoms will borrow or loan out electrons to attain a full outer electron shell. If an atom has just one or two electrons in its outer or valence shell, it will tend to loan them out. And if an atom is one or two electrons short of having a full outer or valence shell, it will tend to borrow electrons to emulate an inert gas, which is an element that has a full outer electron shell. That said, let's look at another idea.

Atoms with just one or two electrons in their valence shells really want to get rid of them (loan them out), and atoms that are only one or two electrons away from having a full valence shell really want to borrow electrons to filll their outer shells. Sure, loaning out or borrowning electrons leaves the atom with an overall charge. You knew that. The overall charge is because of the imbalance that will result when the number of electrons in an atom does not equal the number of protons in its nucleus. And you already knew that an atom with an overall charge (because of the charge imbalance) is called an ion. But the atoms "don't care" about the charge imbalance as long as their valence shell is full. Those things said, let's look at the left and right sides of the Periodic Table and see what's going on.

The left side of the periodic table is where we find the Group 1 and Group 2 metals. These are the Alkali and Alkaline earth metals, respectively. They have only one (in the case of Group 1 elements) or two (in the case of the Group 2 elements) electrons in their valence shells. And these elements really want to get rid of those electrons. On the other side of the periodic table we find the Group 17 elements, which are the halogens. These elements are only one electron short of having a full valence shell, and they really want to borrow one.

When an element that really wants to loan out an electron or two meets an element that really wants to borrow an electron, an ionic bond will form. This is because the elements involved in bonding really want to loan or borrow electrons. These elements are said to be highly reactive. Reactivity is based on the "desire" of an atom to loan or borrow an electron or electrons. The more willing to loan or borrow electrons an element is, the more reactive it is. And when the elements that most want to loan electrons hook up with the elements that most want to borrow them, the strongest chemical bonds form, and these are the ionic bonds.

Answer 2

Metals lose electrons to the non-metals, which gain electrons, in order to achieve a noble gas configuration, and therefore become stable. Take for example, sodium and chlorine. A sodium atom will lose one electron to a chlorine atom, and become an ion with a 1+ charge. This causes the sodium ion to have the electron configuration of the noble gas neon. The chlorine atom becomes an ion with a 1- charge. This causes the chloride ion to have the noble gas configuration of argon. The oppositely charged ions form an electrostatic attraction between them called an ionic bond.

Answer 3

The metal gives up its electrons to the nonmetal, which causes the metal to form a positively charged ion and the nonmetal to form a negatively charged ion. They do this in order to achieve a noble gas configuration, or an octet, making them stable. The electrostatic attraction between the oppositely charged ions forms the ionic bond.