The elements that have the same valence are, mainly, in the same principal groups (principal columns) of the periodic table.
The principal columns are 1, 2, 13, 14, 15, 16, 17 and 18.
For example:
1) the elements with valence 1+ are in the first column:H, Li, Na, K, Rb, Cs, Fr.
2) The elements with valence 2+ are in the second column: Be, Mg, Ca, Sr, Ba, Ra.
3) The elements with valence 2- are in the column 16: O, S, Se, Te, Pb
But also those elements may have other valences: S, Se and Te, have also valences 2, 4 and 6. And Pb have valences 2 and 4.
4) The elements with valences 1-, 1, 3, 5 and 7 are in the column 17: Cl, Br, I, At.
F, the first element of group 16, has valence 1- and 1+
Answer: I don't know if this helps you or not, but this is from study.com:
I'm so sorry if it doesn't:
Explanation: Iron(III) oxide reacts with carbon monoxide according to the balanced equation:
Fe₂O₃ + 3CO ➡️ 2Fe + 3CO₂
A reaction mixture initially contains 23.00g Fe₂O₃ and 15.40g CO.
