<u>Explanation:</u>
Atomic number is defined as the number of protons or electrons that are present in a neutral atom.
Atomic number = number of protons = number of electrons
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons
The isotopic representation of an atom is: 
where,
Z = Atomic number of the atom
A = Mass number of the atom
X = Symbol of the atom
1) Fe
The atom given to us is iron. It is present in Group 8 and period 4 of the periodic table. The atomic number of iron is 26
2) Be
The atom given to us is beryllium. It is present in Group 2 and period 2 of the periodic table. The atomic number of beryllium is 4
3) Kr
The atom given to us is krypton. It is present in Group 18 and period 4 of the periodic table. The atomic number of iron is 36
1) 
Atomic number = Number of protons = Number of electrons = 24
Mass number = 53
Number of neutrons = 53 - 24 = 29
The number of protons, electrons and neutrons for the given element are 24, 24 and 29 respectively
2) 
Atomic number = Number of protons = Number of electrons = 44
Mass number = 103
Number of neutrons = 103 - 44 = 59
The number of protons, electrons and neutrons for the given element are 44, 44 and 59 respectively
3) 
Atomic number = Number of protons = Number of electrons = 30
Mass number = 67
Number of neutrons = 67 - 30 = 37
The number of protons, electrons and neutrons for the given element are 30, 30 and 37 respectively
1) Atomic number = 14; Mass number = 28
The element having atomic number '14' is Silicon
The isotopic symbol of the element is 
The symbol of the element is 'Si'
2) Atomic number = 18; Mass number = 40
The element having atomic number '18' is Argon
The isotopic symbol of the element is 
The symbol of the element is 'Ar'
3) Atomic number = 19; Mass number = 39
The element having atomic number '19' is Potassium
The isotopic symbol of the element is 
The symbol of the element is 'K'
