Page 55 - NCERT Science Class 10 English Medium

K state. For example, gold, silver, platinum and copper are found in the
free state. Copper and silver are also found in the combined state as
Na
their sulphide or oxide ores. The metals at the top of the activity series
Electrolysis
Ca (K, Na, Ca, Mg and Al) are so reactive that they are never found in
nature as free elements. The metals in the middle of the activity series
Mg
(Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s
Al crust mainly as oxides, sulphides or carbonates. You will find that
the ores of many metals are oxides. This is because oxygen is a very
Zn reactive element and is very abundant on the earth.
Thus on the basis of reactivity, we can group the metals into the
Fe
Reduction using following three categories (Fig. 3.9) – (i) Metals of low reactivity; (ii) Metals
carbon
Pb of medium reactivity; (iii) Metals of high reactivity. Different techniques
are to be used for obtaining the metals falling in each category.
Cu
Several steps are involved in the extraction of pure metal from
Ag ores. A summary of these steps is given in Fig.3.10. Each step is
Found in native explained in detail in the following sections.
Au state

Figure 3.9
Figure 3.9
Figure 3.9
Figure 3.9
Figure 3.9
Activity series and
related metallurgy

Figure 3.10
Figure 3.10
Figure 3.10
Figure 3.10
Figure 3.10 Steps involved in the extraction of metals from ores
3.4.2 Enrichment of Ores
Ores mined from the earth are usually contaminated with large amounts
of impurities such as soil, sand, etc., called gangue. The impurities must
be removed from the ore prior to the extraction of the metal. The processes

50 Science

2024-25