Introduction:
In the year 1800, only ………elements were known.
a) 34
b) 118
c) 105
d) 84
In the year 1974, only ……… elements were known.
a) 118
b) 105
c) 38
d) 76
At present ………. elements are known.
a) 118
b) 76
c) 38
d) 116
Out of 118 elements……elements are natural.
a) 38
b) 84
c) 114
d) 94
Explanation:At present, 118 elements are known to us. All these have different properties. Out of these 118, only 94 are naturally occurring. As different elements were being discovered, scientists gathered more and more information about the properties of these elements.
….…….elements are artificially prepared.
a) 28
b) 24
c) 24
d) 92
