When atoms lose or gain electrons to achieve a stable electron configuration, they form ions. Ions are atoms that have a net positive or negative charge. These ions are held together by electrostatic forces to form ionic compounds.

To understand how electrons interact when forming an ionic bond, let's consider the example of sodium (Na) and chlorine (Cl) atoms. Sodium has one valence electron, which is loosely bound to the nucleus, while chlorine has seven valence electrons. The electron configurations of Na and Cl can be represented as:

Na: 1s²2s²2p⁶3s¹

Cl: 1s²2s²2p⁶3s²3p⁵

For sodium to achieve a stable configuration (like neon), it needs to lose one valence electron. Chlorine, on the other hand, needs to gain one electron to complete its valence shell and become like argon. When these atoms come close together, the sodium atom transfers its loosely held valence electron to the chlorine atom.

The loss of an electron from sodium results in the formation of a positively charged sodium ion (Na+), while the gain of an electron by chlorine results in the formation of a negatively charged chloride ion (Cl-). These oppositely charged ions are strongly attracted to each other, forming an ionic bond.

In an ionic bond, the electrostatic forces between the positively and negatively charged ions are relatively strong, resulting in a stable compound. The strength of an ionic bond depends on the charges of the ions involved and the distance between them. The greater the charges and the shorter the distance, the stronger the ionic bond.