chemistry 12th class cbse notes


These are naturally occurring chemical substances in the in the earth crust obtainable by mining.


Only a few minerals are used as sources of that metal. Such minerals are known as ores.


Ores are usually contaminated with earthly or undersides materials known as gangue.


The entire scientific and technological process used for isolation of the metal from its ores is known as metallurgy.

Modes of Occurrence of elements

Metals occur in two forms in nature (i) in native state (ii) in combined state, depending upon their chemical reactivities.

  1. Native State: Elements which have low chemical reactivity or noble metals having least electropositive character are not attacked by oxygen, moisture and CO2 of the air. These elements, therefore, occur in the free state or in the native state, e.g., Au, Ag, Pt, S, O, N, noble gases, etc.
  2. Combined State: Highly reactive elements such as F, CI, Na, K, etc., occur in nature combined form as their compounds such as oxides, carbonates sulphides, halides, etc.

Hydrogen is the only non-metal which exists in oxidized form only.

The occurrence of Metals: Minerals and Ores

  • Minerals: The naturally occurring substances in the form of which the metals occur in the earth crust are called minerals.
  • Ore: Every mineral is not suitable for the extraction of the metal. The mineral form which the metal is economically and conveniently extracted is called an ore.

Thus, all ores are minerals but all minerals are not ores.


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