Science: Chemistry help

Hi all,

I was wondering if there was a way I could interpret how many charges each element had by looking at the periodic table? I know metals have positive charges and halogens negative, but any advice would be appreciated!

Reply 1

QuantumC

Original post by Veqz

Hi all,

I was wondering if there was a way I could interpret how many charges each element had by looking at the periodic table? I know metals have positive charges and halogens negative, but any advice would be appreciated!

Hi!

Yes, the Periodic Table is great for that. I think to begin with (in true persnickety chemistry style) we need to address the wording of the question. Halogens are not negatively charged. The ion formed by a halogen, a halide, will be negatively charged. Likewise, a metal ion will be positively charged. I'll assume you're familiar with how ions are formed?

To determine the size of the charge (+1, +2, -1, -2 etc) we look at the group each element is in. The group number tells you how many electrons are in the outer shell of an atom of an element. For example, fluorine and chlorine are in group 7, hence we know that an atom of chlorine or fluorine has 7 electrons in its outer shell.

Once we know the number of outer electrons, we look at whether it is a metal or a non-metal. The easiest way for metals to gain a full outer electron shell is by losing their outer electron(s), whereas it is easier to non-metals to gain electron(s). For example, it would be easier for a chlorine atom to gain 1 electron than to lose 7 electrons for a full outer shell of 8 electrons. Because chlorine now has gained an electron, it has 18 electrons and 17 protons, meaning it now (a chloride ion) has a net (overall) charge of 1-.

Likewise, this can be applied to other groups:

•

Group 1 metals lose one electron. Ions have a 1+ charge.

•

Group 2 metals lose two electrons. Ions have a 2+ charge.

•

Group 3 metals lose three electrons. Ions have a 3+ charge.

•

Group 6 non-metals gain two electrons. Ions have a 2- charge.

•

Group 7 non-metals gain one electron. Ions have a 1- charge.

I hope this has cleared it up a bit :smile:

it gets a little messy with the transition metals because they have variable valency (can form ions with different charges), so a question should give you the oxidation state of a transition metal for you to work out how many electrons it loses. So to summarize, look at group number, determine metal / non-metal, work out how it will form an ion and how the number of subatomic particles changes as a result.

I LOVE CHEMISTRY XD

Reply 2

Veqz

OP

4

Hi!

Yes, the Periodic Table is great for that. I think to begin with (in true persnickety chemistry style) we need to address the wording of the question. Halogens are not negatively charged. The ion formed by a halogen, a halide, will be negatively charged. Likewise, a metal ion will be positively charged. I'll assume you're familiar with how ions are formed?

To determine the size of the charge (+1, +2, -1, -2 etc) we look at the group each element is in. The group number tells you how many electrons are in the outer shell of an atom of an element. For example, fluorine and chlorine are in group 7, hence we know that an atom of chlorine or fluorine has 7 electrons in its outer shell.

Once we know the number of outer electrons, we look at whether it is a metal or a non-metal. The easiest way for metals to gain a full outer electron shell is by losing their outer electron(s), whereas it is easier to non-metals to gain electron(s). For example, it would be easier for a chlorine atom to gain 1 electron than to lose 7 electrons for a full outer shell of 8 electrons. Because chlorine now has gained an electron, it has 18 electrons and 17 protons, meaning it now (a chloride ion) has a net (overall) charge of 1-.

Likewise, this can be applied to other groups:

•

Group 1 metals lose one electron. Ions have a 1+ charge.

•

Group 2 metals lose two electrons. Ions have a 2+ charge.

•

Group 3 metals lose three electrons. Ions have a 3+ charge.

•

Group 6 non-metals gain two electrons. Ions have a 2- charge.

•

Group 7 non-metals gain one electron. Ions have a 1- charge.

I hope this has cleared it up a bit :smile:

it gets a little messy with the transition metals because they have variable valency (can form ions with different charges), so a question should give you the oxidation state of a transition metal for you to work out how many electrons it loses. So to summarize, look at group number, determine metal / non-metal, work out how it will form an ion and how the number of subatomic particles changes as a result.

Original post by QuantumC

I LOVE CHEMISTRY XD

Haha, yeah thanks. Really helped.

Science: Chemistry help

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