How do you count the valence electrons of an atom?

Answer 1

Take the atomic number then subtract the amount of valence electrons.

Example:

Number of non valence (inner) electrons in Sulfur:

16 (atomic number) - 6 (valence electrons) = 10 (valence or inner electrons)

Answer 2

The number of valence electrons is just how many electrons an atom has in its outer shell. It's easy to figure out if you've got a Periodic Table.

(See the link below this answer for a good periodic table).

All the elements in each column have the same number of electrons in their outer shells. All the elements in the first column all have a single valence electron (H, Li, Na, K, etc.).

The second column elements all have 2 valence electrons (Be, Mg, Ca, Sr, etc.).

Skipping over the gap, go to the Group 3 elements, which all have 3 valence electrons (B, Al, Ga, etc.).

The elements in the next column (C, Si, Ge, etc.) all have 4 valence electrons.

The elements in the next column (N, P, As, etc.) all have, yes, you guessed it, 5 valence electrons.

O, S, Se, and the others in this column have 6 valence electrons.

The halogens in the next-to-last column (F, Cl, Br, etc.) have 7 valence electrons.

The noble gases in the right-most column (Ne, Ar, Kr, etc.) all have 8 electrons in their out except for He, which only has 2 electrons.

In column 1 all of those elements have 1 valence electron.

In column 2 there are 2 valence electrons. He(Helium) is included here.

Skip columns 3 to 12 because their valence electrons vary.

Column 13 has 3 valence electrons.

Column 14 has 4 valence electrons.

Column 15 has 5 valence electrons.

Column 16 has 6 valence electrons.

Column 17 has 7 valence electrons.

Column 18,except for He(Helium), has 8 valence electrons.

Answer 3

The number of valence electrons in an atom (ion) could easily be found by looking at the group number of that element. Nitrogen (N) has five valence electrons, and is in group 5A. Radium has two valence electrons and is in group 2A. The elements in the d and f block of the periodic table (the transition metals and inner transition metals) technically have two valence electrons, but this is usually changed when they are involved in bonding.

Answer 4

For the main group elements, you can use the group number to determine the number of valence electrons.

group 1 - 1 valence electron

group 2 - 2 valence electrons

group 13 - 3 valence electrons (13 - 10)

group 14 - 4 valence electrons (14 - 10)

group 15 - 5 valence electrons (15 - 10)

group 16 - 6 valence electrons (16 - 10)

group 17 - 7 valence electrons (17 - 10)

group 18 - 8 valence electrons (18 - 10)

Answer 5

For the main group elements (s and p blocks), valence electrons are the electrons in the outermost (highest energy) s and p sublevels. The number of valence electrons for the main group elements are as follows:

Group 1 - 1 valence electron

Group 2 - 2 valence electrons

Group 13 - 3 valence electrons (13-10)

Group 14 - 4 valence electrons (14-10)

Group 15 - 5 valence electrons (15-10)

Group 16 - 6 valence electrons (16-10)

Group 17 - 7 valence electrons (17-10)

Group 18 - 8 valence electrons (18-10)

In transition metals, some inner-shell electrons are also valence electrons, so the number of valence electrons is not as easy to predict.

Answer 6

The number of valence electrons is the number in its outer shell. Understanding how shells fill is key to this. For instance, silicon has an atomic number of 14 and it shells are filled 1s2 2s2 2p6 3s2 3p2, so it has four valence electrons.

Answer 7

To find the no. of valence electrons in an atom, write its electronic configuration such that all the shells are completely filled. The last shell will be incomplete i.e., it will have less than 8 electrons.

The no. of electrons in that shell is the no. of valence electrons.

For example:-

Sodium has a configuration of 2,8,1. It has 1 valence electrons.

Chlorine has a configuration of 2,8,7. It has 7 valence electrons.

Answer 8

Group 1 has 1 valence electron.

Group 2 has 2.

Take the group number and subtract 10 from the rest of the groups following the transition metals.

In Group 13, they have 3 valence electrons.

In 14, 4

In 15,5

In 16, 6

In 17, 7

But, in group 18, there is already 8 valence electrons. Thus, making the elements in group 18 stable.