Discovery and Properties of anode, cathode rays neutron and Nuclear structure Questions in English

(D) neutral atom consists of a central nucleus containing protons and neutrons,surrounded by electrons in the extranuclear region. Since the atomic number $Z > 1$,the atom contains at least one proton,one neutron (except for protium),and one electron.

(A) The nucleus of an atom consists of protons and neutrons. These particles are collectively known as nucleons.

(C) The radius of the nucleus is approximately $10^{-15} \ m$ (or $1 \ fm$).
Therefore,the correct option is $(C)$.

(A) The neutron was discovered by $James \ Chadwick$ in $1932$. The reaction is represented as: $_4^9Be + _2^4He \rightarrow _6^{12}C + _0^1n$.

(B) The specific charge ($e/m$ ratio) is calculated as follows:
$1$. For an electron $(e)$: Charge = $-1$,Mass $\approx \frac{1}{1837} \ amu$. Ratio $\approx 1837$.
$2$. For a proton $(p)$: Charge = $+1$,Mass $\approx 1 \ amu$. Ratio = $1$.
$3$. For an alpha particle $(\alpha)$: Charge = $+2$,Mass $\approx 4 \ amu$. Ratio = $0.5$.
$4$. For a neutron $(n)$: Charge = $0$,Mass $\approx 1 \ amu$. Ratio = $0$.
Comparing these values,the electron has the highest $e/m$ ratio.

(D) The density of a neutron is calculated by dividing its mass by its volume.
Given the mass of a neutron is approximately $1.67 \times 10^{-27} \ kg$ and its radius is approximately $10^{-15} \ m$.
Using the volume formula for a sphere $V = \frac{4}{3} \pi r^3$,the volume is approximately $4.18 \times 10^{-45} \ m^3$.
The density is $\rho = \frac{m}{V} \approx 4 \times 10^{17} \ kg/m^3$.
Converting $m^3$ to $cc$ $(1 \ m^3 = 10^6 \ cc)$,the density becomes $4 \times 10^{11} \ kg/cc$.
Thus,the order of magnitude is $10^{11} \ kg/cc$.

(C) This is because chargeless particles do not undergo any deflection in an electric or magnetic field,making them difficult to detect using traditional particle detection methods.

(B) The nucleus of an atom contains protons and neutrons,which are collectively known as nucleons. Electrons are present in the extra-nuclear region revolving around the nucleus. Therefore,the correct option is $(B)$.

(B) Cathode rays are made up of negatively charged particles (electrons) which are deflected by both the electric and magnetic fields.

(B) The mass of a $Neutron$ is approximately $1.675 \times 10^{-27} \ kg$.
The mass of a $Proton$ is approximately $1.673 \times 10^{-27} \ kg$.
The mass of an $Electron$ is approximately $9.109 \times 10^{-31} \ kg$.
$Mesons$ have variable masses,but generally,the $Neutron$ is considered the heaviest among the fundamental subatomic particles listed.
Therefore,the correct option is $(B)$.

(B) The penetration power of a particle is inversely proportional to its mass.
Since a proton is approximately $1837$ times heavier than an electron,its ability to penetrate matter is significantly lower than that of an electron.
$\text{Penetration power} \propto \frac{1}{\text{mass}}$
Therefore,the penetration power of a proton is less than that of an electron.

(C) An elementary particle or fundamental particle is a subatomic particle that is not composed of other smaller particles,meaning it has no substructure.

(C) proton is the nucleus of a hydrogen atom ($H$-atom) that has lost its electron. When a hydrogen atom $(H)$ loses its single electron,it forms a hydrogen ion $(H^+)$,which consists solely of a proton.

(B) Cathode rays are made up of negatively charged particles (electrons,$e^-$).

(A) Anode rays,also known as canal rays,were discovered by $E. Goldstein$ in $1886$ using a discharge tube with a perforated cathode.

(A) The radius of an atom is typically in the range of $10^{-10} \ m$ or $1 \ \mathring{A}$.
Converting this to centimeters,$10^{-10} \ m = 10^{-8} \ cm$.
Therefore,the order of the radius of an atom is $10^{-8} \ cm$.

(C) neutron is a subatomic particle found in the nucleus of an atom. It has a mass slightly greater than that of a proton and carries no net electric charge. Therefore,the net charge of a neutron is $0$.

(B) Unlike protons and electrons,which are electrically charged,neutrons have no charge and are electrically neutral.
The mass of a neutron is approximately $1$ atomic mass unit $(amu)$,which is slightly greater than the mass of a proton.
One atomic mass unit is approximately $1.67 \times 10^{-27} \ kg$.

(D) Cathode rays possess both mass and charge.
Cathode rays are streams of electrons,which are negatively charged particles.
Since electrons have a mass of $9.109 \times 10^{-31} \ kg$ and a charge of $-1.602 \times 10^{-19} \ C$,cathode rays also exhibit these properties.
The ratio of $e / m$ for a cathode ray is constant at $1.758820 \times 10^{11} \ C / kg$,which confirms they consist of particles with mass and charge.

(C) The correct option is $C$. The size of the nucleus is measured in Fermi,where $1 \ \text{Fermi} = 10^{-15} \ \text{m}$.

(D) The discovery of the $Proton$ is attributed to $E. \text{ Rutherford}$.
$J.J. \text{ Thomson}$ discovered the $Electron$.
$J.H. \text{ Chadwick}$ discovered the $Neutron$.
$Isotopes$ were discovered by $Frederick \text{ Soddy}$,not $Bohr$. Therefore,the pair $Bohr-Isotope$ is incorrectly matched.

(C) The proton was discovered by $E. Goldstein$ in $1886$ through his experiments with anode rays (canal rays) in a discharge tube.

(A) The minimum real charge that can exist on any independent particle is the elementary charge,which is the charge of an electron $(e^-)$.
Its value is $1.6 \times 10^{-19} \ C$.
No free particle can possess a charge smaller than this fundamental unit of charge.

(B) The nature of anode rays (also known as canal rays) depends upon the nature of the residual gas present in the discharge tube. Unlike cathode rays,which consist of electrons and are independent of the gas used,anode rays consist of positive ions formed by the ionization of the gas molecules.

(C) The size of an atom is approximately $10^{-10} \ m$ (or $1 \ \mathring{A}$).
Since the electron resides within the atomic orbital,its average distance from the nucleus is of the same order of magnitude as the atomic radius,which is $10^{-10} \ m$.

(A) Specific charge is defined as the ratio of charge $(q)$ to mass $(m)$,i.e.,$\frac{q}{m}$.
For a proton $(p)$: Charge $= 1e$,Mass $= 1 \text{ amu}$. Specific charge $= \frac{1e}{1} = 1e$.
For an $\alpha$-particle $(\alpha)$: Charge $= 2e$,Mass $= 4 \text{ amu}$. Specific charge $= \frac{2e}{4} = 0.5e$.
The ratio of specific charge of a proton to an $\alpha$-particle is $\frac{1e}{0.5e} = \frac{2}{1}$,which is $2:1$.

(B) The mass of a proton $(m_p)$ is approximately $1.672 \times 10^{-27} \ kg$.
The mass of an electron $(m_e)$ is approximately $9.109 \times 10^{-31} \ kg$.
The ratio $m_p / m_e$ is calculated as:
$m_p / m_e \approx (1.672 \times 10^{-27}) / (9.109 \times 10^{-31}) \approx 1836 \approx 1.8 \times 10^3$.
Therefore,the correct option is $(B)$.

(C) The correct option is $(C)$.
$A$ positron $(+1e^0)$ is the antiparticle of an electron $(-1e^0)$.
Both particles have identical mass,which is approximately $9.109 \times 10^{-31} \ kg$.

(C) The mass of an electron is approximately $\frac{1}{1837}$ times the mass of a proton.
Therefore,the ratio of the mass of an electron to the mass of a proton is $1:1837$.

(C) The mass of an atom is primarily concentrated in its nucleus.
The nucleus consists of protons and neutrons.
Electrons have negligible mass compared to protons and neutrons.
Therefore,the mass of an atom is constituted mainly by $Neutron$ and $Proton$.

(C) The nucleus of an atom consists of protons and neutrons only.
Electrons are subatomic particles that revolve around the nucleus in specific orbits.
Therefore,the number of electrons present inside the nucleus of any atom,including $^{12}C$,is $0$.

(D) normal Hydrogen $(H)$ atom consists of only one proton and one electron. It does not contain any neutrons in its nucleus. Therefore,it is the only element that lacks neutrons.

(C) Rutherford's experiment on scattering of $\alpha$-particles showed for the first time that the atom has a nucleus.
He observed that the positively charged $\alpha$-particles were repelled and deflected by the concentrated positive charge at the center of the atom.
Rutherford named this positively charged central portion of the atom as the nucleus.

(A) Rutherford's $\alpha$-particle scattering experiment demonstrated that the positive charge and most of the mass of an atom are concentrated in a very small central region called the nucleus.
Thus,the experiment provided direct evidence for the existence and size of the nucleus.

(C) The nuclear reaction is: $^9_4Be + ^4_2He \rightarrow ^{12}_6C + ^1_0n$.
Neutrons are neutral particles (chargeless),which is why they are not deflected by electric or magnetic fields.
They are also highly penetrating due to their lack of charge.

(D) The experimental evidence for the existence of the atomic nucleus was provided by the Rutherford $\alpha$-particle scattering experiment.
In this experiment,a beam of $\alpha$-particles was directed at a thin gold foil.
The observation that some $\alpha$-particles were deflected at large angles and some even bounced back led to the conclusion that the positive charge and most of the mass of the atom are concentrated in a very small central region called the nucleus.

(D) The radius of a nucleus $(R)$ is experimentally found to be proportional to the cube root of its mass number $(A)$.
This relationship is given by the formula $R = R_0 A^{1/3}$,where $R_0$ is a constant approximately equal to $1.4 \times 10^{-13} \ cm$ (or $1.4 \ fm$).

(C) According to Rutherford,an atom consists of a nucleus which is small in size but carries the entire mass $(P + N)$ of the atom.

(C) The positive charge of an atom is due to the presence of protons,which are located in the nucleus. Therefore,the positive charge is concentrated at the nucleus.

(D) The $e/m$ ratio (specific charge) is calculated as follows:
$(I)$ For neutron $(n)$: Charge = $0$,Mass = $1$,so $e/m = 0/1 = 0$.
$(II)$ For $\alpha$-particle $(\alpha)$: Charge = $ 2$,Mass = $4$,so $e/m = 2/4 = 0.5$.
$(III)$ For proton $(p)$: Charge = $ 1$,Mass = $1$,so $e/m = 1/1 = 1$.
$(IV)$ For electron $(e)$: Charge = $-1$,Mass = $1/1837$,so $e/m = 1/(1/1837) = 1837$.
Comparing these values: $0 < 0.5 < 1 < 1837$.
Therefore,the increasing order is $n < \alpha < p < e$.

(C) The discovery of the atomic nucleus was made by $Ernest \ Rutherford$ in $1911$ through his famous $\alpha$-particle scattering experiment, also known as the $Geiger-Marsden$ experiment.
In this experiment, a thin gold foil was bombarded with $\alpha$-particles, and the observation that some particles were deflected at large angles led to the conclusion that the positive charge and most of the mass of the atom are concentrated in a very small region called the nucleus.

(D) Radius of nucleus $r_n = 1.25 \times 10^{-13} \times A^{1/3} \ cm$.
Given $A = 64$,$r_n = 1.25 \times 10^{-13} \times (64)^{1/3} = 1.25 \times 10^{-13} \times 4 = 5 \times 10^{-13} \ cm$.
Radius of atom $r_a = 1 \ \mathring{A} = 10^{-8} \ cm$.
Volume of nucleus $V_n = \frac{4}{3} \pi (r_n)^3$.
Volume of atom $V_a = \frac{4}{3} \pi (r_a)^3$.
Fraction of volume occupied $= \frac{V_n}{V_a} = \frac{(r_n)^3}{(r_a)^3} = \left( \frac{5 \times 10^{-13}}{10^{-8}} \right)^3 = (5 \times 10^{-5})^3 = 125 \times 10^{-15} = 1.25 \times 10^{-13}$.

(D) The positron is the antiparticle of the electron. Both the positron and the electron have the same mass,which is approximately $9.11 \times 10^{-31} \ kg$.

(D) Positronium is a short-lived exotic atom consisting of an electron $(e^-)$ and its antiparticle,a positron $(e^+)$,bound together in an atom-like system.
It is analogous to a hydrogen atom,where the proton is replaced by a positron.

(A) positron is the antiparticle of an electron,having the same mass but a positive charge.
The charge of a positron is $+1.602 \times 10^{-19} \ C$.
The charge of a proton is also $+1.602 \times 10^{-19} \ C$.
Therefore,the charge on a positron is equal to the charge on a proton.

(B) The neutrino is an elementary particle that interacts only via the weak subatomic force and gravity.
It has a charge of $0$ and its mass is extremely small,effectively considered $0$ in many contexts,which is why they are often referred to as ghost particles.

(D) The correct answer is $(D)$.
Mesons (specifically muons,$\mu$) have a mass approximately $200-300$ times that of an electron and carry either a positive $(+ve)$ or negative $(-ve)$ charge.

(B) is the correct answer.
Carl David Anderson discovered the positron in $1932$ while studying cosmic rays.

(D) standard atom is composed of three fundamental sub-atomic particles: $Protons$,$Neutrons$,and $Electrons$.
While a $Positron$ (the anti-particle of an electron) can be produced during certain types of radioactive decay (such as $\beta^+$-decay),it is not a permanent or fundamental constituent of a stable atom.

(B) The discovery of the neutron was achieved by the bombardment of beryllium with alpha particles.
The nuclear reaction is represented as:
$_4Be^9 + _2He^4 \to _6C^{12} + _0n^1$
Thus,the correct option is $B$.