Answer:
When a sodium atom that has lost an electron comes near a chlorine atom that has gained an electron, an ionic bond is formed.
Step-by-step explanation:
The bonds which are produced between a metal ion and a non-metal ion are termed as ionic bonds. Sodium is metal while chlorine is a non-metallic element, ionic bonds are formed in between them.
Sodium has one electron in its outer most shell whereas a chlorine atom has seven electrons in its outermost shell. To become stable, sodium donates its electron to the chlorine atom and hence ionic bond is formed between them.