Question

How to give the expected charges on ions? When do you know it is a positive or negative?

Answer 1

You can partly use the periodic table. The elements in the s block like to create positive ions while the elements to the right in the p block like to create negative ions. You can say that the tendency to create negative ions increase as you move closer to F in the periodic table.
so some examples Na and K are far away from F so they like to make positive changes (also in the s block). While oxygen is next to F and therefor like to create negative ions.

Answer 2

Is there a more simpler way to remember this :( ?

Answer 3

Hmmmm.... maybe.
In the attachment, we can in most cases (I can't address the importance of that there are exceptions) say that the blu elements create negative ions... except H and He.

Answer 4

When you are on the line between blu and gray you just have to know.

Answer 5

how do you just know? :(

Answer 6

I mean H and group 18.

Answer 7

It is the electronegativity that determines it. Heard about electronegativity before?

Answer 8

yes... but I am not sure how I would know from electronegativity, can you please explain?

Answer 9

Sure. The electronegativity is a measure of how good the elements "pull" in their electrons. For example F is having a high electronegativity, meaning that it won't get rid of them and if it can, it want more... creating a F-
Na is having a very low electronegativity meaning that it does not pull that good in it's electron in the 2s orbital. So it is very easy to remove.
Get the idea? :)

Answer 10

so Na would be Na+? and for the other elements? I understand what you wrote but I don't know how I would know for the other elements...

Answer 11

We can make a little guessing game?
The electronegativity gets higher when we approach F, so I'm gonna write some elements and you are going to guess if they create negative or positive ions.

Answer 12

Potassium (K):
Cholorine (Cl):
Hydrogen (H):
Magnesium (Mg):

Answer 13

K+, Cl-, H- and Mg + ?

Answer 14

Hydrogen is a little special and usually make H+ but else that is totally right! Mg also make 2+ ions, as it got 2 electrons to give away.

Answer 15

Oh yea another good rule:
The most likely ion an element would create (for period 2 and 3) is such that the element most easily obey the octet principle.

Answer 16

so how do you know exactly how many ions? for example Mg, how do you know that is 2+?

Answer 17

Can you please help

Answer 18

Beacuase it is in group two: I'm gonna go over it in your other question.