Respuesta :
Answer :
(1) Number of neutrons: 44
Number of protons: 34
Number of electrons: 36
(2) Element symbol: Ni
Number of protons: 29
Number of electrons: 28
(3) Element symbol: Kr
Mass number: 78
Charge: 0
Explanation :
Atomic number : It is defined as the number of protons or number of electrons.
Atomic number = number of protons
Mass number : It is defined as the sum of number of protons and number of neutrons.
Number of neutrons = Mass number - Atomic number
Part 1:
Element = Se (selenium)
Mass number = 78
Atomic number = 34
Charge on Se = -2
Atomic number = Number of protons = 34
Number of electrons = Number of protons - charge = 34 - (-2) = 36
Number of neutrons = Mass number - Atomic number = 78 - 34 = 44
Part 2:
Mass number = 65
Number of neutrons = 36
Charge on Se = +1
Number of neutrons = Mass number - Atomic number
36 = 65 - Atomic number
Atomic number = 65 - 36 = 29
Atomic number = Number of protons = 29
Number of electrons = Number of protons - charge = 29 - (+1) = 28
The symbol of element is, Nickel (Ni)
Part 3:
Number of neutrons = 42
Number of protons = 36
Number of electrons = 36
Atomic number = Number of protons = 36
Number of neutrons = Mass number - Atomic number
42 = Mass number - 36
Mass number = 42 + 36 = 78
Number of electrons = Number of protons - charge
36 = 36 - charge
Charge = 0
The symbol of element is, Krypton (Kr)