Pls answer and btw I use BJU

Explanation:

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.

Isotopic notation:       Protons            Neutrons          Electrons

        ¹⁹⁷₇₉Au                  79                      118                    79

Solution:

p+n = atomic mass = 79+118 = 197

e = 79  (atomic number)               so the element with atomic number Au.

Isotopic notation:       Protons            Neutrons          Electrons

        ⁷⁹₃₅Br                    35                        44                    35

Solution:

Number of neutrons = atomic mass - number of protons=  79-35 = 44

Number of protons and electrons are equal so number of electrons are 35.

Isotopic notation:       Protons            Neutrons          Electrons

        ¹²⁷₅₃I                          53                    74                      53

Solution:

The atomic number of iodine is 53.

Number of neutrons = atomic mass - number of protons= 127-53 = 74

Number of protons and electrons are equal so number of electrons are 53.

Isotopic notation:       Protons            Neutrons          Electrons

        ⁵⁶₂₆Fe                        26                       30                    26

Solution:

The atomic number of iron is 26.

atomic mass = n+p= 26+30= 56

Number of protons and electrons are equal so number of electrons are 26.