# Homework Help: [Chemistry] How many electrons an element will gain or lose?

1. Oct 15, 2017

### PhyiscsisNeat

1. The problem statement, all variables and given/known data

Predict how many electrons will most likely be gained or lost by each element:

In this case, Gallium

2. Relevant equations

None (that I know of)

3. The attempt at a solution

I know that Gallium is a metal, and metals tend to lose electrons to become cations, so I will assume that Ga will be losing electrons. At the top of the column in which Ga resides sits the term 3A, which I understand to be the number of valence electrons each element in the column has. Beyond this, I have no idea what I am doing. Can someone explain how to predict how many electrons a given element will gain or lose? Thank you in advance.

2. Oct 15, 2017

### I like Serena

Hi PhyiscsisNeat! :)

So it's in group 3A out of 8 groups in total (in the 'A' system).
That means it has 3 electrons in its outer shell that it can release (up to Ga3+).
Or alternatively it can complete its outer shell by attracting up to 5 electrons (up to Ga5-).
Wiki (link) says that the oxidation states of Ga are 3,2,1,-1,-2,-4,-5.

3. Oct 15, 2017

### PhyiscsisNeat

Thank you! The electron lose and gain was confusing me... I guess I wasn't there that day. Finished the assignment with a 99.5%. Thanks again.

4. Oct 15, 2017

### Staff: Mentor

You are most likely expected to assume the element will "fill the octet" - that is, it will either lose or gain electrons till it has an octet on the outermost shell.

That's only an approximation, and a poor one, of what can really happen in reality.

5. Oct 15, 2017

### I like Serena

If I'm not mistaken it only really holds true for elements in group 1, which only seem to have the +1 valency.
Elements in 7A (or 15B) will have -1, but can still have various positive valencies.
It's only oxygen that seems to be pretty consistent at -2 isn't it?

6. Oct 15, 2017

### Staff: Mentor

It works a bit better when we try to predict the most stable configuration only (-1 for all halogens), plus in most cases it is a "natural" (whatever it means) valence for many other elements. Or, to put it differently: for each element the octet rule predicts one of its valencies, the lighter the element, the more common/basic this valence is.

H2O2, OF2

7. Oct 24, 2017

### SciencewithDrJ

Well, Gallium electron shell configuration is Argon 3d10 4s2 4p1. This means that the first 18 electrons are configured in shells just like Argon (Noble Gas). That leaves 13 more electrons to account for. On the third shell level (which is d) are 10 electrons. That leaves 3 electrons left at the 4th shell level. Those last 3 electrons are therefore the valence of Gallium (exactly like the valence of Aluminum, which is also 3). This means that Gallium, like Aluminum will be ready to lose 3 electrons and have a +3 charge, therefore it is a cation.

That's why you would expect Gallium, like Aluminum, to react with three chlorine atoms to form Gallium Trichloride, just like Aluminum would (GaCl3).

This is a simplified explanation, I hope it helps.

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