Use a copy of the Periodic Table where you need one.
A student compared these four particles, Mg2+, Ne, O2− and Al3+. Which conclusion about these four particles is correct?
Source: 2026 XMS Sec 3 WA1 Q4
An ion, X2+, has 10 electrons and 14 neutrons. What is the nucleon number of X?
Source: 2026 XMS Sec 3 WA1 Q5, adapted
An isotope of element Z has 20 neutrons and 17 protons. Which is the correct symbol for an ion of the isotope of element Z?
Source: 2024 CGS Sec 4 Prelim P1 Q4
An atom of one isotope of chlorine is represented by the symbol 37Cl. Particle R has one more neutron, two more protons and one more electron than this isotope of chlorine. Which symbol represents R?
Source: 2025 CHIJ Sec 4 Prelim P1 Q4
Which ion has the most number of shells that contain electrons?
Source: BLSS 2024 Sec 4 Prelim P1 Q5
An ion X2+ contains 19 neutrons and 18 electrons. Which row shows the proton number and nucleon number of X correctly?
| proton number | nucleon number | |
|---|---|---|
| A | 16 | 35 |
| B | 18 | 37 |
| C | 19 | 38 |
| D | 20 | 39 |
Source: 2020 SJI Year 3 End-of-Year P1 Q10
The table gives the number of protons, neutrons and electrons in some particles. The letters do not represent the symbols of the elements.
| particle | protons | neutrons | electrons |
|---|---|---|---|
| A | 17 | 18 | 18 |
| B | 17 | 20 | 17 |
| C | 17 | 18 | 17 |
| D | 16 | 16 | 16 |
| E | 16 | 16 | 18 |
Source: 2020 XMS Sec 3 WA1 B1(a), adapted
The table shows some information about atoms of the elements P, Q, R and S. The letters do not represent the symbols of the elements.
| element | protons | neutrons | nucleon number | electronic configuration |
|---|---|---|---|---|
| P | 16 | 16 | 32 | 2.8.6 |
| Q | 12 | 12 | 24 | 2.8.2 |
| R | 18 | 22 | ||
| S | 17 | 18 | 35 | 2.8.7 |
Source: 2020 SJI Year 3 End-of-Year P2 A3, adapted
Uranium exists as isotopes, uranium-235 and uranium-238. Uranium has proton number 92.
Source: 2024 SMSS Sec 3 End-of-Year P2 Q3(a), adapted
There are three isotopes of hydrogen, shown in Table 10.1. Heavy water, D2O, is water in which the hydrogen atoms are replaced by deuterium. Heavy water is used as a scientific tracer to monitor biological and chemical processes. Heavy water is chemically similar to ordinary water, and scientists can detect atoms of different masses using a technique called mass spectrometry.
| isotope | protons | neutrons | electrons | nuclide notation |
|---|---|---|---|---|
| hydrogen | 1 | 0 | 1 | 11H |
| deuterium | 1 | 1 | 1 | |
| tritium | 1 | 2 | 1 |
| name of ion | chemical symbol | number of electrons |
|---|---|---|
| hydrogen ion | H+ | |
| hydride ion | H− |
Source: 2026 XMS Sec 3 WA1 Q8, adapted
Argon is used as a filler gas in light bulbs as it provides an inert environment and prevents unwanted reactions from happening.
Source: 2026 XMS Sec 3 WA1 Q7(d)
Flerovium, Fl, has proton number 114. To make flerovium, atoms of plutonium (proton number 94) are bombarded with ions of element X. The nucleus of one atom of plutonium combines with the nucleus of one atom of element X to form the nucleus of one atom of flerovium.
Source: 2024 AMKSS Sec 4 Prelim P2 Q4(a), adapted
CThey have the same number of electrons.[1]
Mg2+, Ne, O2− and Al3+ each have 10 electrons, arranged as 2.8.
D26[1]
X2+ has 2 fewer electrons than protons, so protons = 10 + 2 = 12. Nucleon number = 12 + 14 = 26.
C3717Z−[1]
The nucleon number is 17 + 20 = 37 and the proton number is 17. Only a negative ion fits the options with these numbers.
D40K+[1]
Chlorine-37 has 17 protons, 20 neutrons and 17 electrons. R has 19 protons (potassium), 21 neutrons and 18 electrons. The nucleon number is 19 + 21 = 40 and the charge is 19 − 18 = +1.
DS2−[1]
Dproton number 20 and nucleon number 39[1]
X2+ has 18 electrons, so the atom has 18 + 2 = 20 electrons and 20 protons. Nucleon number = 20 + 19 = 39.
A and E[1]
Both have more electrons than protons.
B and C[1]
Both have 17 protons but different numbers of neutrons (20 and 18).
17 + 20 = 37[1]
Sulfur (proton number 16)[1]
2− or −2[1]
It has 16 protons and 18 electrons.
Nucleon number 40 and electronic configuration 2.8.8[1]
R has a stable electronic configuration, with eight electrons in its valence shell (an octet), so it is unreactive.[1]
Atoms of the same element with the same number of protons but different numbers of neutrons.[1]
Isotopes of the same element have the same number of valence electrons.[1]
They have the same number of protons but different numbers of neutrons.[1]
Both have 92 protons.[1]
Uranium-235 has 143 neutrons (235 − 92) while uranium-238 has 146 neutrons (238 − 92).[1]
orSame proton number but different nucleon numbers.
Deuterium 21H and tritium 31H (D and T are accepted as symbols)[1]
Hydrogen, deuterium and tritium atoms each contain one proton.[1]
A deuterium atom has one more neutron than a hydrogen atom, while a tritium atom has two more neutrons than a hydrogen atom (use of data).[1]
They all have one positively charged proton and one negatively charged electron, so they have equal numbers of positive and negative charges.[1]
Heavy water has similar chemical properties to ordinary water, so it will not disrupt biological processes and can be used in the same way in the body.[1]
Deuterium atoms are twice as heavy as hydrogen atoms, so they can be detected using techniques such as mass spectrometry.[1]
| name of ion | chemical symbol | number of electrons |
|---|---|---|
| hydrogen ion | H+ | 0 |
| hydride ion | H− | 2 |
Both correct[1]
Argon has the electronic configuration 2.8.8.[1]
It is unreactive because it has a fully filled valence shell.[1]
Calcium[1]
The proton numbers add up: 94 + 20 = 114.