Question

What type of oxides are formed by metals?

Answer 1

Metals usually form basic oxides e.g. sodium, potassium, calcium. Meaning, the pH of the oxides is greater than 7 on the pH scale. pH is calculated as the negative logarithm of concentration of hydronium ions. Metals form oxides because upon dissolution, they release oxide ions which in turn give hydroxide (basic) ions. However, a few metals form oxides which are both acidic and basic, called amphoteric oxides e.g. zinc, lead.
Generally, group $1$ and group $2$ metal hydroxides are soluble and rest are insoluble in nature.
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