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This all depends on the element's atomic number (number of protons). Since atoms have the same number of protons as they do electrons, the atomic number is essentially equal to the number of electrons as well. For example Aluminum atomic There are lists, but you can just tell anyway according to which group they are in. Eg, elements in the same column as Ca have 2 outer electrons (and a valency of +2), elements in the same column as Na have 1 outer electron (and a valency of +1). At the other end of the table, elements in the same column as Cl have 7 outer electrons, and a valency of -1 (8-7=1). work it out- you don't need a list.

the number of electrons is equal to the atomic number

Valence electrons are the electrons in the outer shell of the atom, just figure out which subshell is the outershell and then you will be able to work out the valence electrons.

s shell holds 2

p shell holds 6

d shell holds 10

f shell holds 14 See the Related Questions. Also, see the related links to download a .pdf version of a periodic table that lists the electron configuration for each element.

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16y ago

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