Question

Which ion in the ground state has the same electron configuration as an atom of neon in the ground state?

Answer 1

• Cl-

Lets see how

• Z for Cl is 9
• One electron is added so new Z=10

Electronic configuration

• 1s²2s²2p⁶

Or

• [Ne]

option B is correct

Answer 2

Answer:

Option 4, $O^{2-}$

Explanation:

Step 1:  Determine which option is correct

We know that Ne has 10 electrons therefore we need to find a different ion that has the same amount.  

Option 1 → Ca has 20 electrons and with 2+ we would remove 2 of those which would leave us with 18.

Option 2 → Cl has 17 electrons and with a - we would add 1 of those which would leave us with 18.

Option 3 → Li has 3 electrons and with a + we would remove 1 of those which would leave us with 2.

Option 4 → O has 8 electrons and with a 2- we would add 2 of those which would leave us with 10.  

Since the only one that matches up in the number of electrons is $O^{2-}$ we can conclude that option 4 is correct.

Answer:  Option 4, $O^{2-}$