IB · IB Chemistry
IB Chemistry: The nuclear atom — Practice Questions & Answers
304 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
What is the relative charge of a neutron?
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WhyProtons carry a relative charge of $+1$, electrons $-1$, and neutrons are neutral with a relative charge of $0$.
2
Multiple choice · Easy
How many protons are present in an atom of $^{23}_{11}\text{Na}$?
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WhyThe atomic number (bottom number) gives the number of protons. For $^{23}_{11}\text{Na}$ the atomic number is 11, so there are 11 protons.
3
Multiple choice · Medium
How many neutrons are in an atom of $^{37}_{17}\text{Cl}$?
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WhyNumber of neutrons = mass number $-$ atomic number $= 37 - 17 = 20$.
4
Multiple choice · Medium
Two isotopes of the same element always differ in their number of:
- Protons
- Electrons
- Neutrons
- Charge
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WhyIsotopes are atoms of the same element (same number of protons) with different numbers of neutrons, giving different mass numbers.
5
Multiple choice · Medium
Chlorine consists of $75\%$ $^{35}\text{Cl}$ and $25\%$ $^{37}\text{Cl}$. What is its relative atomic mass?
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Why$A_{r} = (0.75 \times 35) + (0.25 \times 37) = 26.25 + 9.25 = 35.5$.
6
Multiple choice · Hard
How many electrons are present in the ion $^{40}_{20}\text{Ca}^{2+}$?
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WhyA neutral Ca atom has 20 electrons. The $2+$ charge means it has lost 2 electrons, leaving $20 - 2 = 18$ electrons.
7
Fill in the blank · Easy
An atom of $^{19}_{9}\text{F}$ contains protons.
Answer:
9 / nine
WhyThe atomic number of fluorine is 9, so a neutral fluorine atom contains 9 protons (and 9 electrons).
8
Fill in the blank · Medium
Bromine exists as $50\%$ $^{79}\text{Br}$ and $50\%$ $^{81}\text{Br}$. Its relative atomic mass is .
Answer:
80 / 80.0
Why$A_{r} = (0.50 \times 79) + (0.50 \times 81) = 39.5 + 40.5 = 80$.
9
Multiple choice · Medium
What is the full electron configuration of a ground-state manganese atom (Z = 25)?
- 1s2 2s2 2p6 3s2 3p6 4s2 3d5
- 1s2 2s2 2p6 3s2 3p6 4s2 3d3
- 1s2 2s2 2p6 3s2 3p6 3d7
- 1s2 2s2 2p6 3s2 3p6 4s1 3d6
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WhyApplying the Aufbau principle gives 1s2 2s2 2p6 3s2 3p6 4s2 3d5.
10
Multiple choice · Medium
In forming the Mn2+ ion, which electrons are removed from the manganese atom?
- The two 4s electrons
- Two of the 3d electrons
- Two of the 3p electrons
- One 4s and one 3d electron
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WhyThe 4s electrons are removed before any 3d electrons when a transition metal is ionized.
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