Answer :
(i) The number of atoms present in 7 g of lithium are, 
(ii) The number of atoms present in 7 g of lithium are, 
(iii) The number of moles of
is, 1 mole
The number of moles of
is, 0.5 mole
The number of moles of
is, 1 mole
Explanation :
<u>Part (i) :</u>
First we have to calculate the moles of lithium.

Molar mass of Li = 6.94 g/mole

Now we have to calculate the number of atoms present.
As, 1 mole of lithium contains
number of atoms
So, 1.008 mole of lithium contains
number of atoms
Thus, the number of atoms present in 7 g of lithium are, 
<u>Part (ii) :</u>
First we have to calculate the moles of carbon.

Molar mass of C = 12 g/mole

Now we have to calculate the number of atoms present.
As, 1 mole of carbon contains
number of atoms
So, 2 mole of carbon contains
number of atoms
Thus, the number of atoms present in 7 g of lithium are, 
<u>Part (iii) :</u>
<u>To calculate the moles of </u>
<u> :</u>

Molar mass of
= 38 g/mole

Thus, the number of moles of
is, 1 mole
<u>To calculate the moles of </u>
<u> :</u>

Molar mass of
= 44 g/mole

Thus, the number of moles of
is, 0.5 mole
<u>To calculate the moles of </u>
<u> ions :</u>

Molar mass of
= 17 g/mole

Thus, the number of moles of
is, 1 mole