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Monoatomic Diatomic Polyatomic

Table 5.6
In the table given below, write the number of molecules and the
total number of atoms.
Substance Number of molecules Total number of atoms

O
2
2N
2
6Cl
2
2He
5Na
O
3
P
4
Table 5.7
Compounds

We have seen how molecules are formed from the same type of
atoms. Millions of English words are formed from the letters of
the English alphabet. Similarly, the compounds contain molecules
formed from atoms of different elements (Figure 5.4).

Compound Molecules and Atoms

Molecules Atoms present
Carbon dioxide Carbon, Oxygen

Hydrogen chloride Hydrogen, Chlorine
Water ..........................................
Sugar ..........................................
Mercuric oxide Mercury, Oxygen

Table 5.8
Carbon dioxide is a compound. Carbon dioxide is formed when
carbon burns in oxygen. Carbon dioxide is also formed by the
decomposition of calcium carbonate.
Whatever be the source of a compound, a fixed ratio is maintained
between the atoms of the different elements present in it. In carbon

Basic Science VIII
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