# Homework Help: Chemistry, cations and anions

1. Jul 28, 2011

### gmianosi

1. The problem statement, all variables and given/known data
When does an atom become a cation and an anion?

2. Relevant equations

3. The attempt at a solution

Cations have a positive charge because they lose electrons, and anions have a negative charge because they gain ions. The atom would always want to do what requires the least energy, like if it has 1 electron in its valence shell, it will give it away, becoming a cation, while if it has 6 electrons in it valence shell, it will gain 2, becoming an anion. So basically, if an atom has over 4 electrons in its outer shell, it will become an anion, and if it has under 4, it will become a cation. Now my confusion is, what if it has 4 electrons in it's valence shell.. Like Silicon, does it lose them or gain 4?

I am only referring to when there are 8 electrons in the valence shell.

2. Jul 28, 2011

### pmsrw3

Atoms like carbon and silicon are pretty difficult to ionize. Even nitrogen and boron don't ionize very easily.

3. Jul 28, 2011

### gmianosi

But still, how does silicon ionize? the question is asking me to ionize silicon and lead.. both have 4 electrons in their valence shell

4. Jul 29, 2011

### pmsrw3

Well, reality is a little more complicated than your chemistry text. I think lead usually goes +2 or + 4. Silicon, I don't know. I don't know of any ionic silicon materials. The most common form in nature is silicon dioxide, which suggests +4, but I believe it's actually covalent, not ionic.

5. Jul 30, 2011

### zaldar

The chemistry text is probably wanting you to show that they can do both. Carbon can go to positive or negative depending on what it is with. However in reality it does mostly form covalent compounds as opposed to ionic ones. Oh and it is electrons that it gains or looses not ions. It BECOMES and ion when it has a charge by loosing or gaining ELECTRONS important distinction. I wouldn't give you full credit for the explanation you use.