# If the electron configuration of an element is 1s2 2s2 2p5…

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CHEMISTRY

**If the electron configuration of an element is 1s2 2s2 2p5, how many unpaired electrons are there?**

**A. 2**

**B. 5**

**C. 1**

**D. 4**

**QUICK ANSWER…**

**C**

**SOLUTION…**

**According to Hund's rule one electron must fill each degenerate orbital for each energy level before pairing up.**

**This means the 1S orbital is completely filled, 2S orbital is also completely filled. For the 2P orbital, there are 3 degenerate sub-orbitals which are singly filled so that 2 electrons will be remaining. The remaining two electrons will pair up two of the three sub-orbitals and the remaining sub-orbital will be unpaired.**

**Now for the right answer to the above question:**

**Option A is incorrect.****Option B is incorrect.****C is correct.****D is not the correct answer.**

**QUICK TIPS…**

**You may please note these/this:**

**Always remember that each sub-orbital ought to be singly filled before pairing up.****S orbital has only one sub-orbital.****P orbital has 3 sub-orbitals.****Filling up 5 electrons into these 3 sub-orbitals, two will be paired and one will be unpaired.**

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**/ culled from 2017 JAMB-UTME Chemistry question 18 /**

### Random Question:

2023-01-17 9:16:47 pm by QuizTabletIf the electron configuration of an element is 1s2 2s2 2p5, how many unpaired electrons are there?

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2023-03-16 7:17:00 am by**QuizTablet**

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