How many valence electrons does gold have?

gold nugget

Gold nugget
(credit: pbkwee, cc-by, via flickr)

Gold (Au) is a d-block element and has 1 valence electron (sometimes 3 or even 11 depending on how “valence electron is defined.)

Unlike s-block and p-block elements, you can’t assume the number of valence electrons of d-block elements by counting from left to right. If you follow the periodic table from left to right, gold would have 11 valence electrons.

However Gold most often has chemical reactions with 1 or 3 valence electrons. Reactions with three valence electrons would be marked as gold(III.) If the formula doesn’t connote the usage of gold(III), then gold with one valence electron could be considered.

What is the number of 3s electrons in Mg?

There are two 3s electrons in Mg. You can tell this easily, by looking at the periodic table. Mg is in the third row (3) and second column (s=2.)

This trick works in the p-block as well, so if you look at Oxygen, it’s got the 2s^2 ( because it’s in the 2nd row and it has passed the 2s column), and then it’s the fourth element in on the p-block (p=4.)

So, oxygen’s noble gas configuration is [He] 2s^2 2p^4

1 6 7 8 9