The atomicity of K2Cr2O7 is

1. 9
2. 11
3. 10
4. 12

Explanation: The number of atoms in the molecules of an element is known as its atomicity. In the case of K₂Cr₂O₇, there are 2 atoms of potassium(K), atoms of chromium(Cr) and 7 atoms of oxygen (O). So the atomicity of this compound is the sum of all the atoms present in this compound i.e 2+2+7=11.