# How many valence electrons does a Cl atom have?

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The electron configuration for chlorine, Cl is [Ne]3s23p5. How many valence electrons does a Cl atom have?

Write the symbol for the ion it forms to achieve a noble-gas configuration.

• Seven, it needs to gain one more to achieve noble gas configuration. So if Chlorine gains another electron it will become negative so the symbol would be Cl with a little negative one (-1) or sometimes when the charge is negative one you can just write the negative sign (-) on the upper right side of it (like a power).

Hope this helps.

• To find the valence electrons, find the highest energy level (in this case, 3), and count how many electrons are present in each orbital.

There are 2 in the 3s orbital.

There are 5 in the 3p orbital.

5+2 = 7.

You could also do this just by looking at the periodic table. Chlorine is in column 7 (immediately before the noble gases). This is the halogen group, and all of them have 7 valence electrons (hence the column: 7).

As for the symbol, remember that an atom wants 8 electrons in its outer ring if possible. To do this it will more likely gain 1 than lose 7, so it will be a Chlorine ion with an extra electron. Electrons have a -1 charge each, so we write Cl with a -1 superscript

• chlorine is a halogen or in group 7A meaning it has 7 valence electrons. a noble gas is in group 8A meaning it has 8 valence electrons thus satisfying the octet rule which states that an atom is stable when it achieves a noble gas configuration (full octet). so because chlorine only needs to gain one valence electron to achieve pseudo-noble gas configuration it would have to attain one additional electron giving it a -1 charge.

• Cl has 7 valence electrons

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