Valence Electrons

[AliceBarrington4c]

How do you determine how many valence electrons an element has?

[Miya Eberlein 1J]

The first orbital, the s orbital, can hold two electrons at most. Every shell after the first can hold up to eight electrons. One can tell how many valence electrons an element has by taking its atomic number and seeing how many electrons are left over from the first 2 electrons plus 8 each shell thereafter. For example, Sodium has an atomic number 11, so it has 11 electrons. Since the first orbital is filled first, 2 electrons are taken, leaving nine electrons waiting to be placed. Eight of those nine can go in the next shell, leaving just one valence electron. Hope this is correct + makes sense!

[Victor Qiu 1C]

Valence electrons are the electrons in the outer shell. If we use element carbon as an example. Carbon has the electron configuration [He]2s²2p². We can see that its outer shell is n=2, which is 2s and 2p. Thus, its valence electrons are 2+2=4.

[Simran Bains 2C]

Valence electrons are the number of electrons in the outer orbital. The number of electrons in orbitals go 2, and then 8 from there on. So, if you take P, with 15 electrons, you subtract 2, which gives you 13, then subtract 8, which gives you 5. That's how many valence electrons P has.

[Heidi Buri 2I]

Hi! To determine how many valence electrons and element has, it is helpful to look at the period table, specifically the column number. For groups 1-2 and 13-18, there are specific numbers of valence electrons. Group 1 has one valence electron and group 2 has two valence electrons. Group 13 has 3 valence electrons, group 14 has 4 valence electrons, group 15 has 5 valence electrons, group 16 has 6 valence electrons, and group 17 has 7 valence electrons. Group 18 contains the noble gasses. These all have 8 valence electrons and are very stable.

[Brandon Carris]

All you have to do is write out the electron configuration of the element. The last subshell value will determine the number of valence electrons.

[Audrey Banzali-Marks 1A]

Hi! To add onto the posts above, when you have a positively or negatively charged atom with extra/less-than-usual electrons, you can add (negative) or subtract (positive) the charge from the atomic number to get total amount of electrons in the atom. From there, fill up each shell (2 for the first, 8 for all after) until you have one shell that is incomplete. For example, if you have Ca2+, the neutral Ca atom would usually have 20 electrons and (2+8+8+2=20) 2 valence electrons. However, this Ca2+ ion lost its two valence electrons and now only has 18 electrons. Since every shell is filled completely (1st shell has 2, 2nd and 3rd have 8 each = 18 total electrons), the Ca2+ cation has no valence electrons.

[Rebecca Preusch 2C]

The easiest way to figure out valence electrons is just to look at where the element is on the periodic table. Column 8 has 8 valence electrons, 1 has 1 etc. For transition metals write out the electron configuration and then the valence electrons will be the outermost shell's configuration.

[Desiree Eshraghi 3A]

The last shell of the electron configuration helps you figure out how many valence electrons there are. Just look at the periodic table :)

[Neeti Indiresan 3I]

Valence electrons are the electrons in the outermost shell (largest n value). When you are writing your electron configuration, the number of electrons in your highest n-value energy level should be your valence electrons.

[Dillon Taing 3H]

You can find the number of valence electrons that an element has by looking at what group it is in. The number of valence electrons would correspond to the group number, such as oxygen having 6 valence electrons and being in group 6.

[Gabriel Wolf 3I]

From what I understand, valence electrons are the electrons in the furthermost electron shell, so all you would have to do is figure out what that shell is and count the electrons. For example, carbon and silicon have the same amount of valence electrons, despite silicon having significantly more electrons.

[Shannon Lau 14B - 1H]

Considering how valence electrons are the electrons on the outer most shell of the atom, I usually look at its atomic number to figure it out, then I subtract by 2 considering how the inner most shell right after the nucleus is an s-shell that can hold a maximum of 2 and from the number that I get I divide by 8 and the remainder is the number of valence electrons. If it divides evenly by 8, then that means that the final shell is completely filled and there are 8 valence electrons.

For instance, Carbon's atomic number is 6 so I subtract by 2 and only 4 are left so that is how many valence electrons r left.

Another example, with a greater atomic number would be Lead - Pb with an atomic number of 82. I subtract by 2 giving me 80. Then I divide by 8 and I get 10 which is a whole number revealing that the shells are full so there are 8 valence electrons.