How do you find the charge of an atom?

Question

How do you find out the charge of an atom and what are the steps of doing it? Please give me some examples.

If you need a periodic table here is one: http://en.wikipedia.org/wiki/Periodic_Table

Thank You!

Answer 1

(Atomic number) - (Number of electrons present) = (overall electrical charge of atom)

Answer 2

basically what the guy above me said.

The first line of the periodic table (H, Li, Na) all has a +1 charge

the next column has +2 charge (Be, Mg, Ca)

on the other side of the transition elements column 3 (B, Al, Ga...) has a +3 charge

next column has -4 charge (or a plus four charge some say. It doesn't matter cause it still means it can make four bonds, Carbon, silicon, etc.) nex has -3, then -2, then -1, and the noble gases in the last column have a zero charge and are "perfect".

thats the "quick way to do it if you really wanna just look at the table and be like, "know that charge, know that charge." Now the way its suppsed to be done is as follows:

lets look at Magnesium, second element in column two. it has 12 protons, as we can see from the table, and it therefor has 12 electrons. Since electrons are negatively charged any "extra" electrons give the element a -1 charge. So if i have a magnesium sample and it has two more electrons than it would by itself (12+2=14) then it would have a -2 charge. If it had only ten electrons it would have two more positive electrons than there are negative electrons, so you would have a Mg sample with a +2 charge. Thats all tere is too it, just don't try to overcomplicate it.  

Answer 3

Just so I'm certain, you want to know how to find the common charge of an element or do you want to know how to find all the possible charges?

Well lets start with common charges. So lets say we want to react Sodium(Na) with Chlorine gas(Cl2).

Na + Cl2→

How do we figure out what the product will be? Well you might think NaCl is the product because this is a very commonly known reaction but why NaCl, why not Na2Cl or NaCl3?

Well first we must know the charge of the ion formed by Na, looking at the periodic table you provided, we see that Na is in group 1. This means Na has 1 valence electron. Elements tend to want to have 8 valence electrons so that they can have a stable noble gas configuration. Now Na could have 8 valence electrons by loosing a the one valence electron it has to form Na+. Now you might be saying "How can it have 8 valence after losing 1 valence electron, you just said it only has 1 valence electron so hows that possible?" And that would be a good question. Valence electrons are the outermost s and p electrons. Do you know about electron configurations?

The electron configuration for Na is 1s2, 2s2 2p6 3s1

When we write 1s2 this the 1 is the energy level meaning it's the first energy level, the s is the type of orbital and the 2 is the number of electrons in those types of orbitals in that energy level. So 1s2 means there's 2 electrons in s orbitals in the first energy level. Now when we remove one electron from Na to form Na+ we change it's electron configuration from 1s2, 2s2 2p6 3s1 to 1s2 2s2 2p6. Notice what's different? The 3s1 is now gone because we just removed the 1 electron in that 3s shell so now we're left with 1s2 2s2 2p6 and now the outermost electrons or valence electrons are those in the second energy level, which is the 2s2 and 2p6 part so that's 2+6=8 valence electrons now. Now remember that I previously stated that elements want to have 8 valence electrons to gain a noble gas configuration? Well Now that Sodium has gone from Na to Na+ it now has 8 valence electrons and it has the same electron configuration as the noble gas Neon(Ne) because both Na+ and Ne have 10 electrons. So now that Sodium has a noble gas configuration it is "happy."

You might notice that Na could also gain a noble gas configuration by gaining 7 electrons to form Na^7-. Note: I use the carrot symbol "^" to show that 7- is a superscript which means the charge is -7. I didn't use the "^" symbol for Na+ because I figured you'd be able to figure out that the + sign is a superscript in Na+. Sorry if that causes confusion. Anyways, as I was saying, Na could also gain a noble gas configuration by gaining 7 electrons to from Na^7-. If it gained 7 electrons it would have 18 electrons and have the same configuration as Argon(Ar) so therefore it could be "happy" by gaining 7 electrons but which do you think is easier? Is it easier to gain 7 electrons and form Na^7- or is it easier to lose one electron and form Na+? The answer is, it's much easier to lose 1 electron and form Na+ than it is to gain 7 electrons and form Na^7- so that's why Sodium forms the Na+ ion instead of the Na^7- ion.

Did we really need to write out electron configuration and all that complicated stuff to figure out that Sodium would form Na+? No, it's actually quite simple to figure out what charge elements will have.

The reason Sodium goes from Na to Na+ is because it's in group 1(see periodic table) so it has one valence electron and it gains a noble gas configuration by losing that one valence electron. By losing one electron, Sodium becomes Na+ because now it has one more proton than electron. Originally it had 11 protons and electrons but after losing that one electron it has 11 protons and 10 electrons and since protons are positive it has 1 more positive charge than negative charge so it is now Na+.

Look at where Cl is. See that Cl is in group 17? We ignore the 1 in 17 and only focus on the 7. Cl has 7 valence electrons because it's in group 17. So Now Cl only needs to gain one more electrons to have 8 valence electrons and have a noble gas configuration. Cl will gain one electron so that it can have the same amount of electrons as the noble gas Ar, it forms Cl- because it has gained one electron.

So now, looking at the reaction we were talking about at the start.

Na + Cl2→NaCl

The reason it is NaCl instead of Na2Cl or NaCl3 is because Na has a +1 charge and Cl has a -1 charge so you only need one of each for the charges to cancel out, -1+1=0, so since we only need 1 Na and 1 Cl for the charges to cancel out, the formula is NaCl which means 1 Na and 1 Cl and that is why it is NaCl instead of Na2Cl or NaCl3.

I'll give you a few question with the answer explained.

What charge does the Nitrogen ion have?

N will have a -3 charge because it's in group 15 which means it has 5 valence electrons so it only needs to gain 3 electrons to have 8 valence electrons and the same configuration as Neon(Ne).

What charge will Magnesium ion have?

Mg will have a +2 charge because it's in group 2 so it has 2 valence electrons. It has a +2 charge because it's easier to lose those 2 valence electrons than to gain 6 more electrons and by losing the two electrons it has the same configuration as the noble gas Neon(Ne).

What charge would the Carbon ion have?

Well Carbon is in group 14 so it has 4 valence electrons. Carbon can lose 4 electrons to gain the configuration of the noble gas Helium(He) but it could gain 4 electrons to gain the configuration of the noble gas Neon(Ne). So which do we go with? Will Carbon gain 4 electrons to form Na^4- or will it lose 4 electrons to form Na^4+? Either one is equally likely so Carbon can have a +4 or -4 charge. You have to chose between +4 or -4 for Carbon based on the information you're given.

The same thing goes for Silicon(Si) because it's in the same group, it can have a +4 or -4 charge.

You might be wondering why I skipped over the elements in the middle of the periodic table. The elements in the middle of the periodic table are called transition metals. There's charge is much harder to figure out and they can have many different charges. For example, Vanadium(V) can have a +2, +3, +4 or +5 charge. Basically you have to memorize the charges for the elements in the middle though some periodic tables have numbers above them to show the most common charge in that group. There are a few things you should know about transition metals though, Zinc(Zn) always form an ion with a +2 charge, silver always forms an ion with a +1 charge and the Mercury(I) ion is Hg2^2+, that is Hg2 with a +2 charge. Other than those few exceptions, all the elements in the middle have multiple charges.

That's it for common charges however note that nonmetals such as Nitrogen(N) can have other charges than what you might expect. We expect N to have a -3 charge because it's in group 15 and has 5 valence electrons so it only needs to gain 3 electrons forming N^3- however N can have other charges as well but -3 is the most common one.

I suppose when you learn about oxidation numbers instead of charges you'll start to get this more.

Something you should know: Atoms don't have a charge. A charged atom is called an ion. When we use the term atom in chemistry we're usually referring to neutral substances. For example if I say an atom of Nitrogen that would be interpreted as N without a charge. If I say an ion of Nitrogen that would be interpreted as N with a charge.

And the last thing is how to figure out the charge of an element in a compound.

Example: FeCl2

Well you know Fe has a -1 charge because it's in group 17 so it has 7 valence electrons and only needs to gain 1 electron to have 8 and to have to same configuration as the noble gas Argon(Ar). So Cl has a -1 charge, knowing this we can figure out the charge of Fe in FeCl2. If Cl is -1 and there's 2 Cl's in FeCl2 then that must mean that Fe has a +2 charge because 2 Cl's would have a total of -2 charge so Fe must have a +2 charge for the compound to be neutral.

I couldn't quite tell what you were asking about so if that's not what you wanted to know, feel free to email me and rephrase the question. Perhaps elaborate more and give some example of what you're trying to figure out. I'd be happy to help you out if I can.