# Number of rotons, neutrons and electrons

When I am filling out a table for atomic no, mass no, no of protons, no of neutrons, no of electrons how do I find out the no of protons, neutrons and electrons when it is Mg2+, s2- and n3-?? How do you know the elctron configuraion?

Posted Tue 5th June, 2012 @ 11:12 by Josie Wilders

## 1 Answer

Well this is actually quite easy. Ill tell u why!! Also i have made a recent comment on this on a similar post :

http://getrevising.co.uk/forums/topics/ionic_charges

Now if was not an ion then it wuld be just Mg which is neutral. Wot does that mean, it means that there is equal number of protons and electrons as there is no charge!!

Now if it is Mg2+ then that means that there are more protons then electrons. This means that the Mg had lost two electrons because there are two more protons then electrons.

Now wot does this mean about its electron configuration.

Mg has an electron configuration of 2,8,2

Mg2+ has lost two electrons therefore has 2 less then the configuration above meaning its new electron configuration is 2,8  ===> see how they have a full outer shell now (look at the previous post for this!!).

Now let me tell u a fact n it is easy to remember!!!!!

The proton number or the number of protons always stays the same in a atom!!!!! So that makes life easier!!

Now wot they may ask u is the no. of electrons in Mg2+, then u know that the protons stay the same so u know Mg2+ will have 12 protons and u know becuz it is a 2+ that it has lost 2 electrons then it will have 2 less electron then protons meaning it will have 10 electrons.

Negative ions is the same principal except they have gained electrons

Anyway sorry for not being much help but my other post has most of the answers to your questions. the link is above!!!

Any other questions feel free to post!!!

Answered Tue 5th June, 2012 @ 16:08 by Braniac