# Exercise 4 | Chemical Reactivity

Determine the oxidation number of the metals in the following compounds:

CrO3, KH, CuCl2 and Pb(NO3)2.

CrO3 ⇒ neutral compound and O = -2 ⇒ 0 = x + 3 (-2) ⇒ x = 6
Oxidation state of Cr = +6

KH ⇒ neutral compound and H bonded to a metal = -1 ⇒ 0 = x – 1 ⇒ x = 1
Oxidation state of K = +1

CuCl2 ⇒ neutral compound and Cl = -1 ⇒ 0 = x – 2 ⇒ x = 2
Oxidation state of Cu = +2

Pb(NO3)2 ⇒ neutral compound and NO3 = -1 (corresponding anion is NO3-) ⇒ 0 = x – 2
Oxidation state of Pb = +2