Explanation:
It is more difficult to remove electrons from the second shell or energy level because of the imbalance between the positive nuclear charge and the remaining electrons.
- The amount of energy required to remove electrons in ground state of an atom is the ionization energy.
- The first ionization energy is the energy needed to remove the most loosely bound electron of an atom in the gas phase in ground state.
- The second energy has a greater nuclear pull as it is closer to the nucleus.
- Both potassium and silicon have the same number of energy levels.
The balanced equation between the 
and 
is:
Formula of molarity is:
Substituting the values,
So, number of moles of is 
.
From the balanced equation it is clear that for 1 mole of , 2 moles of are required.
Hence, 0.21 mole of = 
Molar mass of = 
So, the mass of = 
2.2 moles of O2 will be produced by the decomposition of 4.4 moles of water.
There are 3 different elements
C) They have a large number of rods and small number of cones.
