When is an ionic bond formed?

Do ionic bonds occur between metals or non-metals?

How are the electrons transferred?
(from metal to non-metal or non-metal to metal)

Sodium 1s2 2s2 2p6 3s1
Chlorine 1s2 2s2 2p6 3s2 3p5
Which atom will gain an electron and which atom will lose an electron?

If Chlorine gains a negatively charged electron will Chlorine become Cl+ or Cl-

If Sodium has lost an negatively charged electron will it become Na+ or Na-?

Name 5 properties of ionic bonds.