how to find valency of an element

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Question:Okay, so I know that the valency of S in SO4 is 6. And I know that the valency of S in SO3 is 4. But my question is, how to I calculate the valency of an element? I can't figure out why it's 6, or 4 or whatever it may be.

Answers:S has 2 valencies for the reaction with Oxygen: 4 and 6. for the other elements, it depends on the number of electrons on their last layer... for example: Na(sodium) has the number of protons equal with 11 which means the number of electrons is equal with 11. which means layer 1 has 2 electrons, layer 2 has 8 electrons,and the last layer has the last electron ... which gives sodium the valence 1 S has valency 6 and requires 3 atoms of oxygen to result a SO3, and valency 4 because it needs 4 atoms of oxygen to result SO4 and S also has valency 2 for the reaction with metals.

Question:uhh, Let the Element be Chlorine. How do I find it's Valency? uhh but why it needs 8 electrons to become stable? Take Magnesium for instance. its electronic configuration is 2,8,2. Its valency is 2. But why doesnt it need 8 electrons to become stable?

Answers:take the electronic configuration of chlorine...its easy....if the atomic number of Cl is 17 then the electronic configuration of Cl is 2,8,7....so the valency of chlorine is 1...coz chlorine needs 1 eletron to fulfil its octate structure.....so the valency of Cl is 1

Question:I don't get it at all. Like for BrF3. if every single element already has 7 valence electrons, how am I supposed to bond them together so that they follow the octet rule without leaving some bonds out? Also, how do I find the Lewis structure for an element that contains a noble gas (except for He)? Like XeF2 ....Chemistry is so confusing =.=;;

Answers:I don't know the answer to your first question because that confuses me too. But I think I can answer your second question. I think that you can't draw a Lewis structure for something like XeF2 because noble gases are inert; they do not readily react with other elements and thus can't bond. Correct me if I'm wrong but I hope I helped a little bit!

Question:we recently started chemistry in school and our teacher gave us a list of things he called valencies that were like O-2 or iron+1,2or3 or something like that......is there anywhere i can find a list of all the valencies for the periodic table or is there a way to predict the valencies of some elements if your know some?? thanks and any help would be appreciated =) oh and could you say wich ones are posotive valecies and wich ones are negative beacause i dont know how to tell the difference thanks (i realy suck at this stuff lol)

Answers:I will give you a link to a periodic table that will help with "valencies" called oxidation states. Just click on the element and page down the window that comes up. The information will appear under the heading of oxidation states. Happy reading. :)