Problem

According to Table 17.3, the oxide coating that forms on silver should be nonprotective, a...

According to Table 17.3, the oxide coating that forms on silver should be nonprotective, and yet Ag does not oxidize appreciably at room temperature and in air. How do you explain this apparent discrepancy?

Table 17.3 Pilling–Bedworth Ratios for a Number of Metals/Metal Oxidesa

	Protective			Nonprotective
Metal	Oxide	P–B Ratio	Metal	Oxide	P–B Ratio
Al	Al2O3	1.29	K	K2O	0.46
Cu	Cu2O	1.68	Li	Li2O	0.57
Ni	NiO	1.69	Na	Na2O	0.58
Fe	FeO	1.69	Ca	CaO	0.65
Be	BeO	1.71	Ag	AgO	1.61
Co	CoO	1.75	Ti	TiO2	1.78
Mn	MnO	1.76	U	UO2	1.98
Cr	Cr2O3	2.00	Mo	MoO2	2.10
Si	SiO2	2.14	W	WO2	2.10
			Ta	Ta2O5	2.44
			Nb	Nb2O5	2.67