101. Two statements about the proton are given.
Statement I: A proton carries one positive elementary charge.
Statement II: A proton has the same mass as an electron.
ⓐ. Both Statement I and Statement II are true
ⓑ. Statement I is false, but Statement II is true
ⓒ. Statement I is true, but Statement II is false
ⓓ. Both Statement I and Statement II are false
Correct Answer: Statement I is true, but Statement II is false
Explanation: A proton carries charge \(+e\), so Statement I is true. However, the proton mass is far greater than the electron mass. The electron has mass \(9.109\times10^{-31}\,\text{kg}\), while the proton has mass about \(1.6726\times10^{-27}\,\text{kg}\). Equal charge magnitude between proton and electron does not imply equal mass. The false statement comes from mixing up charge comparison with mass comparison.
102. If a neutral hydrogen atom loses its only electron, the remaining ion has charge
ⓐ. \(-e\)
ⓑ. \(+e\)
ⓒ. \(0\)
ⓓ. \(-2e\)
Correct Answer: \(+e\)
Explanation: A neutral hydrogen atom contains one proton and one electron. The proton contributes \(+e\), and the electron contributes \(-e\), so the neutral atom has net charge \(0\). If the electron is removed, the positive proton remains unbalanced. The resulting hydrogen ion is \(\mathrm{H^+}\), with charge \(+e\). Losing a negatively charged electron makes a species more positive, not more negative.
103. Chadwick's experiment is most closely connected with the discovery of the
ⓐ. electron
ⓑ. proton
ⓒ. photon
ⓓ. neutron
Correct Answer: neutron
Explanation: Chadwick is associated with the discovery of the neutron. The neutron is a neutral subatomic particle present in the nucleus. Its discovery helped explain why atomic mass could be greater than the mass expected from protons alone. Earlier cathode-ray and positive-ray studies were connected with electrons and positive particles, but Chadwick's work completed the basic proton-neutron-electron picture. The neutron became essential for explaining mass number and isotopes.
104. A subatomic particle is described as neutral, nuclear, and having mass close to that of a proton. The particle is
ⓐ. neutron
ⓑ. electron
ⓒ. photon
ⓓ. cathode-ray particle
Correct Answer: neutron
Explanation: A neutron has no electrical charge and is present in the nucleus. Its mass is close to the mass of a proton, so it contributes significantly to atomic mass. An electron is negatively charged and much lighter than a proton or neutron. A photon is not a nuclear subatomic particle in the same sense. The clues "neutral" and "mass close to proton" together identify the neutron.
105. A beam of particles passes through an electric field without bending toward either charged plate. If magnetic and other effects are ignored, this observation most strongly suggests that the particles are
ⓐ. positively charged
ⓑ. electrically neutral
ⓒ. negatively charged
ⓓ. electrons with very small mass
Correct Answer: electrically neutral
Explanation: A charged particle is deflected by an electric field because the field exerts force on charge. A positively charged particle bends toward the negative plate, while a negatively charged particle bends toward the positive plate. If a particle beam does not bend toward either plate under the stated condition, it suggests absence of net charge. Neutrons show this kind of behaviour because they are neutral particles. Lack of electric deflection is a charge clue, not a proof of zero mass.
106. The notation \(n^0\) is used for a neutron. The superscript \(0\) mainly represents
ⓐ. zero charge
ⓑ. zero mass
ⓒ. zero size
ⓓ. zero role in the nucleus
Correct Answer: zero charge
Explanation: In \(n^0\), the superscript \(0\) indicates that the neutron has no electrical charge. It does not mean the neutron has zero mass; neutron mass is close to proton mass. The neutron is a nuclear particle and plays an important role in mass number. The notation is parallel to \(e^-\) for electron and \(p^+\) for proton. Reading the superscript as charge sign avoids confusing neutrality with absence of mass.
107. A comparison of proton and neutron properties is given below.
| Particle | Charge | Approximate relative mass |
|---|
| P | \(+1\) | \(1\) |
| Q | \(0\) | \(1\) |
| R | \(-1\) | nearly \(0\) |
The neutron is represented by
ⓐ. P
ⓑ. R
ⓒ. Q
ⓓ. both P and R
Correct Answer: Q
Explanation: A neutron has relative charge \(0\) and relative mass close to \(1\). Row \(Q\) matches both of these properties. Row \(P\) represents a proton because it has relative charge \(+1\) and relative mass close to \(1\). Row \(R\) represents an electron on the simple relative scale because it has charge \(-1\) and much smaller mass. The neutron is identified by combining its neutral charge with its nuclear-scale mass.
108. Neutrons are important in explaining isotopes because isotopes of an element have
ⓐ. different numbers of protons only in the notation
ⓑ. no electrons in any neutral atom in the notation
ⓒ. identical mass numbers in all cases
ⓓ. different neutron numbers with the same \(Z\)
Correct Answer: different neutron numbers with the same \(Z\)
Explanation: Isotopes are atoms of the same element, so they have the same number of protons and the same atomic number. They differ in neutron number, which changes the mass number. This is why neutrons are essential for explaining how atoms of the same element can have different masses. Changing proton number would change the element itself. Isotopic difference is mainly a neutron-number difference, not an electron-removal idea.
109. Assertion: A neutron does not bend toward either plate in an electric field.
Reason: A neutron has no net electrical charge.
ⓐ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓑ. Assertion is true, but Reason is false
ⓒ. Both Assertion and Reason are true, and Reason explains Assertion
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason explains Assertion
Explanation: A particle bends in an electric field when it carries charge. A neutron has zero net electrical charge, so the electric field does not pull it toward the positive or negative plate in the way it pulls charged particles. The Assertion is true because a neutron is neutral. The Reason is also true and directly explains the observation. The absence of electric deflection should not be misread as absence of mass.
110. A data card for a nuclear particle says:
Symbol: \(n^0\)
Charge: \(0\)
Mass: close to proton mass
The card describes a particle that contributes mainly to
ⓐ. negative charge outside the nucleus
ⓑ. nuclear mass but not nuclear charge
ⓒ. the positive charge of the nucleus
ⓓ. fluorescence in a cathode-ray tube
Correct Answer: nuclear mass but not nuclear charge
Explanation: The particle described is a neutron. Since it is present in the nucleus and has mass close to a proton, it contributes to the mass of the nucleus. Since its charge is \(0\), it does not contribute to nuclear charge. Nuclear positive charge comes from protons, not neutrons. This is why mass number counts neutrons, but atomic number does not.
111. The row that contains a mismatched particle property is
| Row | Particle | Property stated |
|---|
| P | Electron | Charge \(-1\) |
| Q | Proton | Charge \(+1\) |
| R | Neutron | Charge \(+1\) |
| S | Neutron | Mass close to proton mass |
ⓐ. R
ⓑ. P
ⓒ. Q
ⓓ. S
Correct Answer: R
Explanation: A neutron has charge \(0\), not \(+1\). Row \(R\) therefore gives a wrong property for the neutron. An electron has relative charge \(-1\), and a proton has relative charge \(+1\), so rows \(P\) and \(Q\) are consistent. The neutron's mass is close to proton mass, so row \(S\) is also consistent. The common confusion is to group proton and neutron together by mass and then accidentally give both a positive charge.
112. In the notation of atomic structure, atomic number \(Z\) represents the number of
ⓐ. protons in the nucleus
ⓑ. neutrons only
ⓒ. protons plus neutrons
ⓓ. electrons lost by an atom
Correct Answer: protons in the nucleus
Explanation: Atomic number \(Z\) is defined as the number of protons in the nucleus of an atom. It identifies the element because different elements have different proton numbers. Protons plus neutrons give mass number, not atomic number. In a neutral atom, the number of electrons equals \(Z\), but that is a result of neutrality rather than the definition of \(Z\). The definition of \(Z\) must always be tied first to proton count.
113. An atom has atomic number \(Z=13\). The nuclear charge of this atom is
ⓐ. \(-13e\)
ⓑ. \(0\)
ⓒ. \(+26e\)
ⓓ. \(+13e\)
Correct Answer: \(+13e\)
Explanation: \( \textbf{Given data:} \) Atomic number \(Z=13\).
\( \textbf{Meaning of } Z\textbf{:} \) \(Z\) gives the number of protons in the nucleus.
\( \textbf{Proton count:} \) Number of protons \(=13\).
\( \textbf{Charge of one proton:} \) \(+e\).
\( \textbf{Nuclear charge relation:} \)
\[
\text{nuclear charge}=+Ze
\]
\( \textbf{Substitution:} \)
\[
\text{nuclear charge}=+13e
\]
\( \textbf{Final answer:} \) The nuclear charge is \(+13e\). The sign is positive because the nucleus contains protons, not electrons.
114. A neutral atom has \(Z=20\). The number of protons and electrons are respectively
ⓐ. \(20\) and \(18\)
ⓑ. \(18\) and \(20\)
ⓒ. \(40\) and \(20\)
ⓓ. \(20\) and \(20\)
Correct Answer: \(20\) and \(20\)
Explanation: Atomic number \(Z\) gives the number of protons, so the atom has \(20\) protons. In a neutral atom, total positive charge from protons must balance total negative charge from electrons. Therefore, the number of electrons is also \(20\). Neutrons are not needed to decide the charge balance in this question. The equality of protons and electrons applies because the atom is specified as neutral.
115. A species \(X^{2+}\) has atomic number \(Z=12\). The number of electrons in this species is
ⓐ. \(12\)
ⓑ. \(10\)
ⓒ. \(14\)
ⓓ. \(24\)
Correct Answer: \(10\)
Explanation: \( \textbf{Given data:} \) Atomic number \(Z=12\).
\( \textbf{Proton count:} \) Number of protons \(=12\).
\( \textbf{Neutral atom electrons:} \) A neutral atom with \(Z=12\) has \(12\) electrons.
\( \textbf{Meaning of } X^{2+}\textbf{:} \) The \(2+\) charge means the species has lost \(2\) electrons.
\( \textbf{Electron count:} \)
\[
12-2=10
\]
\( \textbf{Charge check:} \) \(12\) protons and \(10\) electrons give net relative charge \(+2\).
\( \textbf{Final answer:} \) \(X^{2+}\) contains \(10\) electrons. A cation has fewer electrons than the corresponding neutral atom.
116. A species \(Y^{3-}\) has atomic number \(Z=15\). Its electron count is
ⓐ. \(18\)
ⓑ. \(12\)
ⓒ. \(15\)
ⓓ. \(30\)
Correct Answer: \(18\)
Explanation: \( \textbf{Given data:} \) Atomic number \(Z=15\).
\( \textbf{Proton count:} \) Number of protons \(=15\).
\( \textbf{Neutral atom electrons:} \) A neutral atom of \(Y\) has \(15\) electrons.
\( \textbf{Meaning of } Y^{3-}\textbf{:} \) The \(3-\) charge means the species has gained \(3\) electrons.
\( \textbf{Electron count:} \)
\[
15+3=18
\]
\( \textbf{Charge check:} \) \(15\) protons and \(18\) electrons give net relative charge \(-3\).
\( \textbf{Final answer:} \) \(Y^{3-}\) contains \(18\) electrons. An anion has more electrons than its corresponding neutral atom.
117. A table lists species of the same element with \(Z=16\).
| Species | Electron count claimed |
|---|
| P. \(X\) | \(16\) |
| Q. \(X^{2-}\) | \(18\) |
| R. \(X^{2+}\) | \(18\) |
| S. \(X^+\) | \(15\) |
The wrong electron-count claim is
ⓐ. P
ⓑ. Q
ⓒ. R
ⓓ. S
Correct Answer: R
Explanation: For \(Z=16\), the neutral atom \(X\) has \(16\) electrons. The anion \(X^{2-}\) has gained \(2\) electrons, so it has \(18\) electrons. The cation \(X^+\) has lost \(1\) electron, so it has \(15\) electrons. The species \(X^{2+}\) should have lost \(2\) electrons and therefore should contain \(14\) electrons, not \(18\). Row \(R\) reverses the cation rule by adding electrons instead of subtracting them.
118. The expression \(+Ze\) for nuclear charge means that
ⓐ. each neutron contributes \(+e\) in the notation
ⓑ. \(Z\) protons, each contributing \(+e\)
ⓒ. each electron contributes \(+e\)
ⓓ. the nucleus has charge \(-Ze\) in the notation
Correct Answer: \(Z\) protons, each contributing \(+e\)
Explanation: Nuclear charge is positive because the nucleus contains protons. Atomic number \(Z\) gives the number of protons, and each proton carries charge \(+e\). Therefore, the total nuclear charge is \(+Ze\). Neutrons do not contribute to nuclear charge because their charge is \(0\). Electrons are outside the nucleus in the basic atomic picture and carry negative charge.
119. A neutral atom is changed into \(M^+\). The change must involve
ⓐ. gain of one electron
ⓑ. gain of one proton from the nucleus
ⓒ. loss of one neutron from the nucleus
ⓓ. loss of one electron
Correct Answer: loss of one electron
Explanation: A positive ion forms when a neutral atom loses one or more electrons. For \(M^+\), the charge is \(+1\), so the atom has lost one electron. Removing a negatively charged electron leaves one extra unit of positive charge from the protons. Changing proton number would change the element, not simply form the ion \(M^+\). Neutron loss would affect mass-related properties but would not directly give the \(+1\) ionic charge.
120. Two species have the same atomic number \(Z=11\). Species P is neutral, while species Q has charge \(+1\). The electron counts of P and Q are
ⓐ. P: \(10\), Q: \(11\)
ⓑ. P: \(11\), Q: \(12\)
ⓒ. P: \(11\), Q: \(10\)
ⓓ. P: \(22\), Q: \(11\)
Correct Answer: P: \(11\), Q: \(10\)
Explanation: \( \textbf{Given data:} \) Both species have \(Z=11\).
\( \textbf{Proton count:} \) Each species has \(11\) protons.
\( \textbf{For neutral P:} \) Electron count equals proton count.
\[
\text{electrons in P}=11
\]
\( \textbf{For Q with } +1\textbf{ charge:} \) Q has lost \(1\) electron compared with the neutral atom.
\[
\text{electrons in Q}=11-1=10
\]
\( \textbf{Charge check for Q:} \) \(11\) protons and \(10\) electrons give net charge \(+1\).
\( \textbf{Final answer:} \) P has \(11\) electrons and Q has \(10\) electrons. A positive ion has fewer electrons, not more electrons.
