Question

Match the element with its oxidation number (charge).

1. +1 O
2. -1 Ca
3. -3 Si
4. -2 Al
5. +2 N
6. +3 Na
7. +/- 4 F

Answer 1

The answer is in the problem

Step-by-step explanation:

As general rule of number of oxygen is -2:

O → -2

Alkali metals (Li, Na, K) are always +1

Na → +1

Alkali earth methals (Be, Mg, Ca...) are always +2

Ca → +2

The halogen group (F, Cl, Br...) is always -1

F → -1

The oxidation number of Si (+/- 4)

Aluminium is, usually +3

And to complete the octet rule in nitrogen, 3 electrons are required. That means:

N → -3