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 \(Z\) (subscript in \(_{55}^{133}Cs\)) represents the number of protons. So, the number of protons \(= 55\).

Step2: Calculate the number of neutrons

The mass number \(A\) (superscript in \(_{55}^{133}Cs\)) is related to the number of neutrons \(N\) and protons \(Z\) by the formula \(A=Z + N\). Given \(A = 133\) and \(Z=55\), we can solve for \(N\): \(N=A - Z\). Substituting the values, \(N = 133-55=78\).

Step3: Find the number of electrons

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

Answer:

E. \(55;78;54\)