Question

using the \criss - cross\ method and your oxidation number chart, choose the correct compound below
chart with oxidation numbers
sodium (na) bonding with oxygen (o)
a nao
b na₂o
c nao₂
d na₁o₁
using the \criss - cross\ method and your oxidation number chart, choose the correct compound below
chart with oxidation numbers
calcium (ca) bonding with nitrate=(no₃) oxidation = 3-
a ca₂(no₃)
b ca(no₃)
c ca₃(no₃)₂

Explanation:

Step1: Determine oxidation numbers

For sodium (\(Na\)) and oxygen (\(O\)): Sodium has an oxidation number of \(+1\) (\(Na^{+}\)), oxygen has an oxidation number of \(-2\) (\(O^{2 -}\)).
Using the criss - cross method, we swap the absolute values of the oxidation numbers. So for \(Na\) and \(O\), we get \(Na_{2}O\) (since we take \(2\) from \(O^{2 -}\) for \(Na\) and \(1\) from \(Na^{+}\) for \(O\), but we don't write the \(1\)).
For calcium (\(Ca\)) and nitrate (\(NO_{3}^{-}\)): Calcium has an oxidation number of \(+2\) (\(Ca^{2+}\)), nitrate (\(NO_{3}^{-}\)) has an oxidation number of \(-1\).
Using the criss - cross method, we swap the absolute values of the oxidation numbers. We get \(Ca(NO_{3})_{2}\) (swap \(2\) from \(Ca^{2+}\) to \(NO_{3}^{-}\) and \(1\) from \(NO_{3}^{-}\) to \(Ca^{2+}\), but we don't write the \(1\) for \(Ca\) and put parentheses around \(NO_{3}\) since it's a polyatomic ion).

Answer:

For sodium and oxygen: B. \(Na_{2}O\)
For calcium and nitrate: None of the options \(a\), \(b\), \(c\) are correct. The correct formula is \(Ca(NO_{3})_{2}\)