Answer:
a) [tex]_{31}^{71}\textrm {P^{3+}}[/tex]
b) [tex]_{35}^{80}\textrm {Br^{-}}[/tex]
c) [tex]_{90}^{232}\textrm {Th^{4+}}[/tex]
d) [tex]_{38}^{87}\textrm {Sr^{2+}}[/tex]
Explanation:
For neutral atoms:
Atomic Number (Z)= number of protons = number of electrons
Mass number (A) = number of protons + number of neutrons
For ions with positive net charge:
Number of protons = Z + net charge
For ions with negative net charge:
Number of protons= Z - net charge
a) A = 71, Charge = +3
Number of electrons = 28
Number of protons = 28 +3 =31
[tex]_{31}^{71}\textrm {P^{3+}}[/tex]
b) A = 35, Z = 45+35=80, Charge = -1
Number of protons =35
Number of neutrons = 45
Number of electrons = 36
Charge = Number of protons- Number of electrons =35-36 = -1
[tex]_{35}^{80}\textrm {Br^{-}}[/tex]
c) Charge = +4
Number of electrons = 86
Number of protons = Z = 86+4 = 90
mass number = A = 90+142 = 232
[tex]_{90}^{232}\textrm {Th^{4+}}[/tex]
d) Charge = +2
Atomic number = Number of protons = Z = 38
mass number = A = 87
[tex]_{38}^{87}\textrm {Sr^{2+}}[/tex]