Question

the condition for the formation of ionic bond between two atoms

Answer 1

The condition for the formation of ionic bonds between 2 atoms is
one atom should gain electron
and other atom should loose electron

Answer 2

The condition for the formation of ionic bond between two elements:
1. One element must be of low ionization potential
2. Another element must be of high electron affinity.
3. The electronegativity difference should be high.

Hope this helps you.