Atomic Structure and the Periodic Table: Practice Questions

Which of the following atoms contains the highest number of neutrons in its nucleus?

The successive ionisation energies ( \(I_E\)) for an element are given below in \(\text{kJ mol}^{-1}\):

\(I_E1: 578\)
\(I_E2: 1817\)
\(I_E3: 2745\)
\(I_E4: 11577\)
\(I_E5: 14830\)

In which group of the Periodic Table is this element located?

The first ionisation energies of the elements in Period 3 show a general increase. However, the first ionisation energy of sulfur (\(Z=16\)) is lower than that of phosphorus (\(Z=15\)).
Which statement provides the best electronic explanation for this evidence of sub-shells?

The first ionisation energies of elements generally increase across Period 3. However, there is a slight decrease in first ionisation energy between magnesium (\(Z=12\)) and aluminium (\(Z=13\)).
Which of the following is the best explanation for this observation?

Chlorine exists as two isotopes, \(^{35}Cl\) and \(^{37}Cl\), in an approximate abundance ratio of 3:1. When a sample of chlorine gas is analysed in a mass spectrometer, peaks corresponding to the molecular ion \(Cl_2^+\) are observed.
What is the expected relative ratio of the peak heights for the ions at \(m/z\) 70, 72, and 74?

State the mass number of an atom that contains 14 protons and 15 neutrons, and identify the element using its chemical symbol.

Define the term first ionisation energy and explain why the second ionisation energy of sodium (\(Z=11\)) is significantly higher than its first ionisation energy.

Successive ionisation energies for an unknown element X are (in \(\text{kJ mol}^{-1}\)): \(I_1=1012\), \(I_2=1903\), \(I_3=2912\), \(I_4=4957\), \(I_5=6274\), \(I_6=21269\), \(I_7=25398\).
Identify the group element X belongs to and explain how this data provides evidence for the existence of quantum shells.

Chlorine exists naturally as two main isotopes, chlorine-35 and chlorine-37.

(a) State what is meant by the term isotope.

(b) The relative atomic mass of chlorine is 35.5. Calculate the relative abundances of the two isotopes, chlorine-35 ( \(^{35}\text{Cl}\) ) and chlorine-37 ( \(^{37}\text{Cl}\) ).

(c) Chlorine forms a chloride ion, \(\text{Cl}^{-}\) . Determine the number of protons, neutrons, and electrons present in the \(^{37}\text{Cl}^{-}\) ion.

A sample of an element X in Period 3 of the Periodic Table is analyzed using a mass spectrometer. The successive ionization energies (\(I_E\)) for X, in \(\text{kJ mol}^{-1}\), are provided below:

\(I_E1: 738\)
\(I_E2: 1451\)
\(I_E3: 7733\)
\(I_E4: 10541\)
\(I_E5: 13630\)

(a) Identify element X and justify your answer by referring to the data provided. (2 points)
(b) Write the full electronic configuration of the ion formed after the second ionization of X. (1 point)
(c) Explain why the third ionization energy is significantly higher than the second ionization energy. (2 points)
(d) Predict whether the first ionization energy of the element immediately to the right of X in the Periodic Table would be higher or lower than \(738 \text{ kJ mol}^{-1}\). Explain your reasoning. (2 points)