Question 1

Which of the following statements best explains why the first ionisation energy decreases as you move down a group in the periodic table?

Accepted Answer

The outer electrons are further from the nucleus and experience more shielding from inner electrons.

Question 2

Given the following electronic configuration for a neutral magnesium atom: $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$, what is the electronic configuration for the $$\mathrm{Mg$$^{2+}$$}$$ ion?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$

Question 3

Which block of the periodic table do the transition metals belong to?

Accepted Answer

d block

Question 4

Why does sulfur have a lower first ionisation energy than phosphorus, despite having more protons?

Accepted Answer

Sulfur's outer electron is paired in a 3p orbital, causing electron-electron repulsion.

Question 5

A mass spectrum of chlorine gas ($$\mathrm{Cl_2$}) $$shows three main peaks at $$m/z$$ values of 70, 72, and 74. Which isotopic combinations correspond to these peaks?

Accepted Answer

Cl-35/Cl-35, Cl-35/Cl-37, Cl-37/Cl-37

Question 6

Which of the following best describes the trend in atomic radius across a period from sodium to argon?

Accepted Answer

Atomic radius decreases due to increased nuclear charge pulling electrons closer.

Question 7

Which of the following is the correct order of filling for the sublevels in an atom according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p$$

Question 8

A mass spectrometer is used to analyze a sample of magnesium. The spectrum shows peaks at $$m/z$$ values of 24, 25, and 26 with relative abundances of 78.7%, 10.13%, and 11.17% respectively. Calculate the relative atomic mass (RAM) of magnesium. (Give your answer to one decimal place.)

Accepted Answer

24.3

Question 9

Which of the following best explains why the first ionisation energy of sodium is much lower than that of neon?

Accepted Answer

Sodium's outer electron is in a higher energy shell and more shielded from the nucleus.

Question 10

Which of the following is the correct definition of first ionisation energy?

Accepted Answer

The energy required to remove one electron from one mole of gaseous atoms.

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 12

Which of the following best describes the use of mass spectrometry in planetary science?

Accepted Answer

To identify the isotopic composition of elements on other planets.

Question 13

Which of the following elements is classified as an s-block element?

Accepted Answer

Sodium (Na)

Question 14

Why is the second ionisation energy of an element always higher than the first?

Accepted Answer

The remaining electrons experience a greater attraction to the nucleus after the first electron is removed.

Question 15

Which of the following best explains the high melting point of silicon compared to phosphorus?

Accepted Answer

Silicon forms a macromolecular structure with strong covalent bonds.

Question 16

Which of the following is the correct formula for calculating the relative atomic mass (RAM) using percentage abundance?

Accepted Answer

$$\mathrm{RAM} = \frac{\sum (	ext{isotopic mass} 	imes \% 	ext{abundance})}{100}$$

Question 17

Which of the following best describes the trend in first ionisation energy across a period?

Accepted Answer

It generally increases due to increasing nuclear charge with similar shielding.

Question 18

Which of the following is a correct statement about the filling of orbitals in the electronic structure of atoms?

Accepted Answer

Each orbital can hold up to two electrons with opposite spins.

Question 19

Which of the following is a real-world application of mass spectrometry?

Accepted Answer

Identifying breakdown products from drugs in the body for drug testing in sports.

Atomic Structure and Periodicity: Study Notes for Introduction to Chemistry

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