anbuitachi

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Hi can someone please explain this to me?


which of the following species has an unpaired electron in its ground-state electronic configuration?
A) Ne
b) Ca+
C.) Na+
D.) O2-

I chose C cause Na in it's ground state has 1 valence electron in the s orbital so its unpaired. But the answer is B.

But since it's wrong ground state obviously mean including the charge in this case? I thought ground state e. configuration is for chargeless elements?
 

Geekchick921

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I can see what you were thinking when you chose B, but they mean ground state as in the atom/ion is not excited, and all of the electrons are in their lowest possible energy level.

In this case, everything but Ca+ has a completed outermost energy shell/noble gas configuration/no unpaired electrons. Ca needs to become Ca 2+ to achieve noble gas configuration, so that Ca+ ion is probably pretty pissed about it and desperately wants to shake off that last, unpaired electron.
 

wagmanager

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you can just count the number of electrons the atom would normally have and add or subtract electrons as needed(depending on the charge) for cations or anions, this leaves na+ with 10, ca+ with 19 , o2- with 18, ne with 10, the one with the odd number of electrons will have unpaired electrons. so answer is ca+