📝 Subatomic particles protons neutrons electrons (13 MCQs)

📖 From Campbell Biology • 2. The Chemistry of Life • 13 questions available

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What is Subatomic particles protons neutrons electrons?

Definition:
Subatomic particles are the smaller constituents of an atom: protons are positively charged particles found in the nucleus, neutrons are neutral particles also in the nucleus, and electrons are negatively charged particles that orbit the nucleus in energy shells; protons and neutrons contribute to the atomic mass, while electrons determine the atom's chemical behavior and reactivity, and the balance of protons and electrons gives the atom its net charge.

Working:
Protons and neutrons reside in the nucleus, and their numbers define the atom's mass number ( $\text{Mass Number} = \text{Protons} + \text{Neutrons}$ ), while electrons occupy orbitals around the nucleus and are involved in chemical bonding; the number of protons (atomic number) identifies the element, and in a neutral atom, the number of electrons equals the number of protons; electrons are arranged in shells, and their interactions determine chemical properties, with the electrostatic force described by Coulomb's law $F = k \frac{q_1 q_2}{r^2}$ .

Example:
A simple example is carbon-12, which has 6 protons, 6 neutrons, and 6 electrons, with the electrons arranged in two shells (2, 4), making carbon tetravalent and able to form four bonds; another example is sodium-23, with 11 protons, 12 neutrons, and 11 electrons, with the electron configuration 2, 8, 1, explaining its reactivity.

Reason:
Understanding subatomic particles is fundamental to chemistry and biology because it explains the structure of atoms, the nature of isotopes, the formation of ions and bonds, and the basis of radioactivity, which is used in medicine and research.

Easy

Medium

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📝 All Subatomic particles protons neutrons electrons MCQs

Q1. An atom has 17 protons and 18 electrons. A student claims it must be a neutral chlorine atom because chlorine has 17 protons. What is the best evaluation of the claim?

A.The claim is correct because electrons do not affect charge

B.The atom is a chlorine ion with a

1-

charge because it has one more electron than proton ✅

C.The atom is a different element because its electron number is 18

D.The atom is neutral because protons and electrons have equal masses

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The number of protons determines the element, so 17 protons identifies chlorine. Because there are 18 electrons, one more negative charge exists than positive charge, giving the particle an overall $1-$ charge.

Q2. Two particles have the following compositions: Particle X contains 8 protons, 8 neutrons, and 8 electrons; Particle Y contains 8 protons, 10 neutrons, and 8 electrons. Which conclusion best explains their relationship?

A.They are different elements because their neutron numbers differ

B.They have different charges because their neutron numbers differ

C.They are isotopes of the same element because they have the same proton number but different neutron numbers ✅

D.They are ions because their neutron numbers are unequal

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: Both particles contain eight protons, which means both belong to the same element. Their different neutron numbers change their masses but not their elemental identity, so they represent isotopes of that element.

Q3. A researcher removes two electrons from a neutral atom without changing its nucleus. Which sequence correctly predicts the changes?

A.Atomic number decreases by 2, mass number stays constant, and charge becomes

2-

B.Atomic number stays constant, mass number stays constant, and charge becomes

2+

✅

C.Atomic number increases by 2, mass number increases by 2, and charge becomes neutral

D.Atomic number stays constant, mass number decreases by 2, and charge becomes

2+

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Removing electrons does not alter the nucleus, so proton number and neutron number remain unchanged. Therefore, atomic number and mass number stay constant, while the loss of two negative charges produces a $2+$ ion.

Q4. An unknown particle has a mass number of 31 and an overall charge of $3-$ . Its nucleus contains 15 protons. How many neutrons and electrons does it contain?

A.16 neutrons and 12 electrons

B.15 neutrons and 18 electrons

C.16 neutrons and 18 electrons ✅

D.31 neutrons and 18 electrons

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Mass number equals protons plus neutrons, so $31-15=16$ neutrons. A $3-$ charge means the particle has gained three electrons relative to 15 protons, giving $15+3=18$ electrons.

Q5. A student says, “If an atom gains an electron, its mass number increases because an electron is a particle with mass.” Which correction is most scientifically appropriate?

A.The mass number increases by exactly one

B.The atomic number increases by one

C.The mass number and atomic number remain unchanged because both depend on the nucleus ✅

D.Both mass number and proton number decrease

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: Mass number counts protons and neutrons in the nucleus, while atomic number counts protons. Gaining an electron changes the atom's charge but does not change either nuclear count, so both values remain unchanged.

Q6. A sample contains three kinds of particles: A has 11 protons, 12 neutrons, and 11 electrons; B has 11 protons, 12 neutrons, and 10 electrons; C has 12 protons, 12 neutrons, and 12 electrons. Which pair represents particles of the same element?

A.A and B ✅

B.A and C

C.B and C

D.All three

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Particles A and B both contain 11 protons, so they are forms of the same element. They differ in electron number and therefore charge. Particle C has 12 protons, so it belongs to a different element.

Q7. A detector records the following relationship between particle count and net charge: 10 protons with 10 electrons gives charge 0; 10 protons with 11 electrons gives charge $-1$ ; 10 protons with 12 electrons gives charge $-2$ . What model best predicts the charge for 10 protons and 9 electrons?

-3

-1

+1

✅

+2

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The data show that each electron contributes one negative charge relative to the fixed ten positive proton charges. With nine electrons, there is one fewer negative charge than positive charge, producing a net $+1$ charge.

Q8. A student compares two atoms and writes: Atom P has 6 protons, 6 neutrons, 6 electrons. Atom Q has 6 protons, 8 neutrons, 6 electrons. The student concludes that Q must have a different atomic number. What is the error?

A.Atomic number depends on electrons, not protons

B.Atomic number depends on neutrons and protons equally

C.Atomic number is determined only by proton number, which is 6 for both atoms ✅

D.Atomic number always equals mass number

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Atomic number is defined by the number of protons in the nucleus. Since both atoms contain six protons, both have atomic number 6. The additional neutrons in Q change its isotope and mass number, not its atomic number.

Q9. A laboratory graph shows net charge on the vertical axis and the number of electrons on the horizontal axis for particles containing 12 protons. The plotted trend decreases by one charge unit whenever one electron is added. Which particle would lie at net charge $-2$ ?

A.A particle with 10 electrons

B.A particle with 11 electrons

C.A particle with 12 electrons

D.A particle with 14 electrons ✅

💡 Difficulty: hard | ✅ Correct: D

📖 Explanation: With 12 protons, a neutral particle contains 12 electrons. Each additional electron decreases net charge by one unit. Therefore, two additional electrons give 14 electrons and a net charge of $2-$ .

Q10. An atom contains 19 protons and 20 neutrons. It loses one electron and then gains two electrons. Compared with the original neutral atom, what is its final state?

A.It has 19 protons, 20 neutrons, and a

1-

charge ✅

B.It has 19 protons, 20 neutrons, and a

1+

charge

C.It has 18 protons, 20 neutrons, and a neutral charge

D.It has 19 protons, 21 neutrons, and a

1-

charge

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The nucleus remains unchanged throughout the electron transfers, so there are still 19 protons and 20 neutrons. Starting neutral, losing one electron gives $1+$ , then gaining two produces a final $1-$ charge.

Q11. A graph compares the relative masses of protons, neutrons, and electrons and shows electrons as having a much smaller mass. A student concludes that electrons therefore have no effect on electrical charge. Which response is best?

A.Correct, because only massive particles can carry charge

B.Incorrect, because electron mass and electron charge are separate properties ✅

C.Correct, because electrons have no physical properties

D.Incorrect, because electrons determine the number of neutrons

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Mass and electric charge are independent properties. Although an electron has far less mass than a proton or neutron, it carries a negative elementary charge and therefore strongly affects the net charge of an atom.

Q12. Particle R contains 13 protons, 14 neutrons, and 10 electrons. Particle S contains 13 protons, 14 neutrons, and 13 electrons. A scientist wants to determine whether the particles differ because of nuclear composition or electron arrangement. What is the strongest conclusion?

A.They have different nuclei because their proton numbers differ

B.They have identical nuclear composition but different electron arrangements ✅

C.They are different elements because their electron numbers differ

D.They must have different neutron numbers

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Both particles have the same 13 protons and 14 neutrons, so their nuclei are identical in composition. Their electron counts differ, meaning they have different charges but the same elemental identity and isotope.

Q13. A hypothetical atom has $Z=9$ and $A=19$ . It is converted into an ion with three more electrons than the neutral atom. Which description correctly models the resulting particle?

A.9 protons, 10 neutrons, 12 electrons, charge

3-

✅

B.9 protons, 19 neutrons, 12 electrons, charge

3+

C.19 protons, 9 neutrons, 12 electrons, charge

3-

D.9 protons, 10 neutrons, 6 electrons, charge

3+

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: The atomic number $Z=9$ gives 9 protons, while $A=19$ gives $19-9=10$ neutrons. A neutral atom has 9 electrons, so adding three gives 12 electrons and a $3-$ charge.

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