I'm stuck on valencies i don't know how to work them out its really hard whats the easiest solution?

Question

Magnesium Pho
sphate?
mg Po4
2 3 How did you get the numbers 2 and 3 i am confused
3 2

I'm revising so please explain really easily

Answer 1

Group number 1 = Valency 1
group number 2 = valency 2
group number 3 = valency 3
group number 4 = valency 4
group number 5 = valency 3
group number 6 = valency 2
group number 7 = valency 1
group number 8 = valency 0 (noble gases, unreactive)
There is no easy way to work out the valency of transition metals (they can have different valencies). I'm guessing you are in high school, in which case I would hope they would tell you in the question.
Roman numerals in the names of the compound tell you the valency of the transition metal.
Complex ions (like phosphate), unfortunately you just have to learn. The valency is the same as the number of charges on the ion.
Phosphate (PO4)3- has a valency of 3
sulphate (SO4)2- has a valency of 2
ammonium (NH4)+ has a valency of 1
nitrate (NO3)- has a valency of 1

Not sure if you know this or not from your question, but just in case......
to work out formulae -
elements/ions Mg PO4
valencies 2 3
swap 3 2
divide if possible (not in this case)
Formula Mg3(PO4)2

Hope that helps

Answer 2

Magnesium is Mg2+ and phosphate is PO4 3-. The formula is Mg3(PO4)2, because it takes 3 x 2+ = 6+ to counter 2 x 3- = 6- for an overall charge of 0.

As for how to know the valences or oxidation numbers of the elements and ions, the bottom answer is that you just have to memorize them. Once you know the numbers, it's possible to reinforce your memory and come to some understanding of the numbers by looking at a Periodic Table. But really, there's no substitute for doing the work.

Answer 3

Memorizing the valences of elements in compounds is an important start. You must also memorize the charges on the compound ions.
The periodic table is organized into families of elements that generally react in a similar fashion so that elements in a vertical column will generally have the same valence. Make a blank copy of the periodic table and enter the symbols of the elements into the table along with their valance(s). A pattern should arise in the table.

Answer 4

Valency Of Nitrate

Answer 5

metals have a valency acoording to how may electrons they lose
so Na would be +1
and Mg 2+
an Al 3+
non metals have a valency depeding on how many elecrtons they gain generally
so o would be o2-
n 2- or 3 -
its the ones like c that need learning
as co3 is 2-
Cl-
SO4 2-
PO4 2-
it has to be 2- as Mg we know is 2+

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Answer 7

1

Answer 8

You can refer to the periodic table then you need to memorize these