How do figure out the ratios in which elements combine

[ryan001]

Hi All

 

I need help figuring out the ratio's in which the elements in period 2 combine with
chlorine and oxygen i.e a method to solve the problem.

Below is an attachment containing the informattion I was given and the question.

 

Thanks in advance I appreciate the help.

Information.zip

[hypervalent_iodine]

How familiar are you with determining charges / oxidation states of ions? As in, if I asked you what the charge on Na is in NaCl, would you know it or how to figure it out?

[ryan001]

As it is I wouldn't be able to provide an answer, but if I knew the value of the ions involved I could try.

[hypervalent_iodine]

What do you mean by the value?

[ryan001]

i.e How many ions each element has lost or gained e.g.Mg²⁺ and Cl^- the superscripts.

Edited July 17, 2014 by ryan001

[hypervalent_iodine]

I think you're confusing electrons with ions. An ion is an element or polyatomic species that is charged - I.e. Has a net loss or gain of electrons. Mg has two valence electrons and will typically lose both of those to give Mg2+. If you can work out the charge (the 2+ in the case of magnesium), working out the combination of that plus a halogen to give a neutral species (a compound where the combined charge equals 0) is relatively easy to do. Take Mg2+ and Cl- for example. To create a neutral species, you need two Cl- ions for every Mg2+ ion, giving MgCl2.

 

This is a very simplistic way of doing it, but since you seem to be dealing with simple compounds it should be fine.

As for working out the charges, there are some general rules for certain groups of elements and the rest you can work out from there.

 

- Elemental forms will always have an oxidation state / charge of 0. This is for things like O2, H2, Na (not Na+), etc.

- hydrogen, unless in elemental form, has a charge of +1, as do the group one elements.

- group two elements have a charge of +2, unless they are in elemental form.

- oxygen is always -2 unless it is in a peroxide, in which case it is -1, or elemental form.

- halogens are always -1 unless in elemental form.

[ryan001]

I am still a bit lost

 

1.One of the given examples in my textbook states that the chloride of Mg is MgCl₂ and that the chloride of P is PCl₅ or PCl_3. How did they come to this conclusion,

the examples are in the attachment in the first post.

I stil don't know how to work this out.

 

2 In the post above you said "- oxygen is always -2 unless it is in a peroxide, in which case it is -1, or elemental form" How do I know this by looking at the periodic table.

Edited July 17, 2014 by ryan001

[Fuzzwood]

How do I know this by looking at the periodic table. <-- notice anything about the columns they are in? Also read up about the octet rule.

[ryan001]

Thanks everyone I appreciate the help.

 

May someone please help with the Questions in post 7