EasyChemistryHigh School (9–10)GeneralCarbon and Its Compounds › Covalent Bonding and AllotropesConceptual
Two chlorine atoms, each 2, 8, 7, join to make Cl₂.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two chlorine atoms, each , join to make . Why do they share a pair of electrons, rather than one atom giving an electron to the other? How many electrons does each atom count in its outer shell afterwards?
Need a reminder? The key ideaShow
A covalent bond is a pair of electrons shared by two atoms. One pair is a single bond, two pairs a double bond, three pairs a triple bond. Valency: H , O , N , C , Cl . Number of bonds, counting a double bond as two, = (sum of the valencies) .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Both want to gain. Each atom needs one more electron. Neither is willing to lose one.
Step 2. Giving would fail. If one gave an electron, it would be left with six outer electrons, further from a full shell.
Step 3. Sharing works. They share one pair. Each counts its own six unshared electrons and both shared ones: electrons.
Answer: both atoms need to gain an electron, so they share one pair, and each then counts outer electrons.
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