Electron configuration

Practice Question Solving
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Can anyone tell me please what’s the correct answer ? With explanation

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hi um what’s the answer that’s given ?

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Not sure if I’m missing something but I worked it out and only Mg2+ and Ne have the same electronic configuration.

Li+ and Na+

  • Li+ has an electronic configuration of 1s2 because the atomic number is 3 but it lost one electron (because of the + charge), so there are only 2 total electrons.
  • Na+ is 1s2 2s2 2p6 because the atomic number is 11 but it lost one electron, so there are only 10 total electrons

So this pair is incorrect.

Mg2+ and Ne

  • Mg2+ would have an electronic configuration of 1s2 2s2 2p6 because the atomic number of Mg is 12 but it lost 2 electrons, so 10 total electrons.
  • Ne has an atomic number of 10, meaning 10 total electrons, so the electronic configuration is also 1s2 2s2 2p6.

So this pair is correct.

Na2+ and Ne

  • we already know this pair is incorrect because even though Na has a 2+ charge this time, we’ve already worked out the Na and Ne electronic configurations above and they do not match.

So this pair is incorrect.

O2- and a carbon atom

  • O has an atomic number of 8, but O has gained 2 electrons here, for a total of 10 electrons, so the electronic configuration is 1s2, 2s2 2p6
  • Carbon has an atomic number of 6, meaning the electronic configuration is 1s2 2s2 2p2

So this pair is incorrect.

this was a long answer so I tried to make it as organised as possible, hope it helps :slight_smile:

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got the same ans but the options don’t correspond. I guess something wrong w the q

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yeah it must be some error!

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