<u>Answer:</u> The mass of chlorine atom required to combine is 35.5 grams.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
 .....(1)
      .....(1)
Given mass of sodium = 23 g
Molar mass of sodium = 23 g/mol
Putting values in equation 1, we get:

According to mole concept:
1 mole of an atom contains  number of particles
 number of particles
So, 1 mole of sodium will contain =  number of atoms
 number of atoms
Number of atoms of chlorine = Number of atoms of sodium =  = 1 mole
 = 1 mole
Now, calculating the mass of chlorine required by using equation 1:
Moles of chlorine = 1 mole
Molar mass of chlorine = 35.5 g/mol
Putting values in equation 1, we get:

Hence, the mass of chlorine atom required to combine is 35.5 grams.