An atom wants 8 valence electrons. It is sometimes referred to as "the magic 8" in chemistry. Except for hydrogen, which wants 2.
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It depends on the atom. List what element the atom is from.
A stable atom has 8 electrons in its outer most valence shell. A simple way to remember this is that all atoms want to be like the noble gases which all have 8 electrons (except helium but the reason is complicated and not necessary here)
Phosphorous has 5 valence electrons. So, you need 3 more to complete it.
CH3CO-OH (acetic acid) has 10 valence electrons. The carbon atom contributes 4 valence electrons, each hydrogen atom contributes 1 valence electron, and the oxygen atom contributes 6 valence electrons.
The molecular formula for phosphoric acid is H3PO4. I'll assume you can count.
Indium has 3 valence electrons.
8 valence electrons- 1s22s2p63s2p6
Zinc has two valence electrons.
5 valence electrons.
Aluminum has 3 valence electrons.
Beryllium has two valence electrons.
3 valence electrons
There are 3 valence electrons in an atom of aluminium.
There are no valence electrons.
Lead has 4 valence electrons.