Question

a _{55}^{133}cs^{+} ion has ______ protons, ____ neutrons, and ______ electrons.
a) 54; 133; 55
b) 55; 133; 54
c) 54; 78; 55
d) 55; 78; 55
e) 55; 78; 54

Explanation:

Step1: Determine the number of protons

The atomic number of an element is equal to the number of protons. For \(_{55}^{133}Cs^{+}\), the atomic number is \(55\), so the number of protons is \(55\).

Step2: Calculate the number of neutrons

The mass number \(A = 133\), and the formula for the number of neutrons \(N\) is \(N=A - Z\), where \(Z\) is the atomic number. Substituting \(A = 133\) and \(Z = 55\), we get \(N=133 - 55=78\).

Step3: Find the number of electrons

For a neutral atom, the number of electrons is equal to the number of protons. But for \(Cs^{+}\), it has lost one electron. So the number of electrons is \(55 - 1=54\).

Answer:

E. \(55;78;54\)