Two Period 3 elements have the following successive ionization energies (in kJ·mol⁻¹):
• Element A: 1012, 1903, 2910, 4956, 6276, 21 000
• Element B: 578, 1817, 2745, 11 580, 14 820, 18 450
Identify Element A and Element B and justify your choices based on the data.