Question

which of these elements has an electron configuration of kr5s²?
barium
calcium
rubidium
strontium

Explanation:

• Barium: Its electron configuration is \([Xe]6s^{2}\).
• Calcium: Its electron configuration is \([Ar]4s^{2}\).
• Rubidium: Its electron configuration is \([Kr]5s^{1}\).
• Strontium: Its electron configuration is \([Kr]5s^{2}\).

Answer:

strontium