Atomic number, Mass number, Atomic species Questions in English

(A) The atomic number of neon $(Ne)$ is $10$,so it has $10$ electrons.
Isoelectronic species are those that have the same number of electrons.
$F^{-}$ has $9 + 1 = 10$ electrons.
$O^{2-}$ has $8 + 2 = 10$ electrons.
$Na^{+}$ has $11 - 1 = 10$ electrons.
$Mg^{2+}$ has $12 - 2 = 10$ electrons.
Among the given options,$F^{-}$ is isoelectronic with neon.

(A) The electronic configuration of the dipositive ion $M^{2+}$ is given as $2, 8, 14$.
The total number of electrons in $M^{2+}$ is $2 + 8 + 14 = 24$.
Since the ion has a $+2$ charge,the neutral metal atom $M$ must have $24 + 2 = 26$ electrons.
Therefore,the atomic number $(Z)$ of the metal is $26$.
The atomic weight $(A)$ is given as $56 \ a.m.u.$
The number of neutrons $(n)$ is calculated using the formula $n = A - Z$.
$n = 56 - 26 = 30$.

(B) sulphur atom $(S)$ has an atomic number of $16$. To achieve a stable noble gas configuration,it gains two electrons to form a sulphide ion $(S^{2-})$.
The process is represented as: $S + 2e^- \to S^{2-}$.

(C) Henry Moseley,through his experiments on $X$-ray spectra of various elements,established that the frequency of $X$-rays emitted by an element is related to its $Z$ (atomic number) rather than its atomic weight. This discovery led to the modern periodic law,which states that the physical and chemical properties of elements are periodic functions of their atomic number.

(A) The chemical behaviour of an atom is primarily determined by the number of electrons in its outermost shell,which is governed by its $Atomic \ number$ $(Z)$.

(B) The atomic number of element $M$ is $9$,which corresponds to Fluorine $(F)$.
The electronic configuration of $M$ is $1s^2 2s^2 2p^5$.
To achieve a stable noble gas configuration $(1s^2 2s^2 2p^6)$,the element needs to gain one electron.
Therefore,it forms an anion represented as $M^{-}$.

(A) The atomic number $(Z)$ of an element is defined as the total number of protons present in the nucleus of its atom.
In a neutral atom,the number of protons is equal to the number of electrons.
The number of neutrons is calculated as the difference between the mass number $(A)$ and the atomic number $(Z)$.
For example,in ${}_{17}^{37}Cl$,the atomic number is $17$,which means there are $17$ protons and $17$ electrons,while the number of neutrons is $37 - 17 = 20$.

(C) Lithium nitride is $Li_3N$.
In this compound,the nitride ion is $N^{3-}$.
The atomic number of nitrogen is $7$,which means it has $7$ protons.
Since the ion has a charge of $-3$,it has gained $3$ electrons.
Therefore,the number of electrons = $7 + 3 = 10$.
Thus,the nitride ion is composed of $7P + 10e$.

(B) The atomic number of an element is defined as the number of protons present in the nucleus of its atom.
During chemical reactions,the number of electrons may change due to the formation of ions,but the number of protons remains constant,making it the fundamental characteristic of an element.

(C) The sodium cation $(Na^+)$ has $11 - 1 = 10$ electrons.
$O^{2-}$ has $8 + 2 = 10$ electrons.
$F^{-}$ has $9 + 1 = 10$ electrons.
$Li^{-}$ has $3 + 1 = 4$ electrons.
$Al^{3+}$ has $13 - 3 = 10$ electrons.
Therefore,$Na^+$ has a different number of electrons from $Li^{-}$.

(B) The atomic number $(Z)$ of hydrogen is $1$,and the mass number $(A)$ of tritium is $3$.
Number of neutrons $= A - Z = 3 - 1 = 2$.

(C) Tritium is an isotope of hydrogen with the symbol $^3_1H$ or $T$.
It consists of $1$ proton,$1$ electron,and $2$ neutrons.
Therefore,the correct option is $(C)$.

(D) The size of hydrogen-like species is given by the formula $r \propto \frac{n^2}{Z}$,where $n$ is the principal quantum number and $Z$ is the atomic number.
For $H$ $(n=1, Z=1)$,$r \propto \frac{1^2}{1} = 1$.
For $He^{+}$ $(n=1, Z=2)$,$r \propto \frac{1^2}{2} = 0.5$.
For $H^{-}$ ($n=1, Z=1$,but with two electrons,the effective nuclear charge decreases due to shielding,leading to a larger size than $H$).
For $Li^{2+}$ $(n=1, Z=3)$,$r \propto \frac{1^2}{3} = 0.33$.
Comparing the values,$Li^{2+}$ has the smallest radius.

(D) .

Species	Total electrons
$P^{3-}$ (Phosphide ion)	$18$
$Cl^{-}$ (Chloride ion)	$18$

$P^{3-}$ and $Cl^{-}$ are isoelectronic species,meaning they have the same number of electrons.

(C) Carbon-$12$,carbon-$13$,and carbon-$14$ are isotopes of carbon. They have the same atomic number but different mass numbers. $A$ $Mass \ spectrometer$ is used to separate and identify particles based on their mass-to-charge ratio $(m/z)$. Therefore,it is the appropriate instrument to differentiate between these isotopes.

(B) The particles present inside the nucleus of an atom are collectively known as nucleons.
These particles are protons and neutrons.
Therefore,$\text{Protons} + \text{Neutrons} = \text{Nucleons}$.

(D) Chemical reactivity is determined by the electronic configuration of an atom.
Since both $C^{12}$ and $C^{14}$ are isotopes of carbon,they possess the same atomic number $(Z = 6)$ and the same electronic configuration $(1s^2 2s^2 2p^2)$.
Therefore,they exhibit identical chemical properties and reactivity.

(C) An ion is an electrically charged atom or a group of atoms.

(D) The atomic weight (or mass number) of an atom is defined as the sum of the number of protons and neutrons in the nucleus.
Adding a neutron increases the total number of nucleons by $1$,which results in an increase in the atomic weight of the atom.
It does not change the number of protons (atomic number) or the number of electrons,so the chemical properties remain the same.

(C) Tritium is an isotope of hydrogen represented as $_{1}H^{3}$.
In this notation,the subscript $1$ represents the atomic number $(Z)$,which is the number of protons.
The superscript $3$ represents the mass number $(A)$,which is the sum of protons and neutrons $(A = Z + N)$.
Since $Z = 1$,the number of protons is $1$.
Since $A = 3$,the number of neutrons $(N)$ is $A - Z = 3 - 1 = 2$.
In a neutral atom,the number of electrons is equal to the number of protons,so there is $1$ electron.
Therefore,the composition is $1$ electron,$1$ proton,and $2$ neutrons.

(D) The number of neutrons $(N)$ in an atom is calculated by subtracting the atomic number $(Z)$ from the mass number $(A)$.
$N = A - Z$
For $_{88}Ra^{226}$,the mass number $A = 226$ and the atomic number $Z = 88$.
$N = 226 - 88 = 138$.
Therefore,the correct option is $(D)$.

(C) The number of neutrons in an atom is calculated as $A - Z$,where $A$ is the mass number and $Z$ is the atomic number.
For $_{18}^{40}Ar$,the number of neutrons is $40 - 18 = 22$.
Now,let us calculate the neutrons for each option:
$A) _{19}^{41}K$: $41 - 19 = 22$ neutrons.
$B) _{21}^{43}Sc$: $43 - 21 = 22$ neutrons.
$C) _{21}^{40}Sc$: $40 - 21 = 19$ neutrons.
$D) _{20}^{42}Ca$: $42 - 20 = 22$ neutrons.
Thus,$_{21}^{40}Sc$ does not have $22$ neutrons.

(B) The nuclear reactivity of an atom or ion depends solely on the composition of its nucleus,specifically the number of protons and neutrons.
Since $Na$ (atomic number $11$,mass number $23$) and $Na^+$ (formed by the loss of an electron) have the same nucleus containing $11$ protons and $12$ neutrons,their nuclear reactivity is identical.

(D) The term $nucleons$ refers to the particles present inside the atomic nucleus.
These particles are protons and neutrons.
Therefore,the total number of nucleons (mass number,$A$) is equal to the sum of the number of protons $(Z)$ and the number of neutrons $(N)$.
$A = Z + N$
Thus,the correct option is $D$.

(A) The correct technique is Mass Spectrometry.
In this technique,charged atoms (ions) are accelerated by an electric field and then deflected by a magnetic field.
The extent of deflection depends on the mass-to-charge ratio $(m/z)$ of the ions,which allows for the determination of the masses of isotopes.
Therefore,option $A$ is correct.

(B) Isotopes are defined as atoms of the same element that have the same atomic number (identical chemical properties) but different mass numbers due to a different number of neutrons (differ in atomic weights).

(D) The isotope of oxygen is represented as $^{18}_{8}O$.
In this notation,the subscript $8$ represents the atomic number $(Z)$,which is the number of protons.
The superscript $18$ represents the mass number $(A)$,which is the sum of protons and neutrons $(A = Z + N)$.
Therefore,the number of neutrons $(N)$ is calculated as $N = A - Z = 18 - 8 = 10$.
Thus,the isotope has $8$ protons and $10$ neutrons.

(A) Isobars are atoms of different elements that have different atomic numbers but the same mass number.
In option $A$,both $_{6}C^{13}$ and $_{7}N^{13}$ have the same mass number $(A = 13)$ but different atomic numbers ($Z = 6$ and $Z = 7$ respectively).
Therefore,$_{6}C^{13}$ and $_{7}N^{13}$ form an isobaric pair.

(C) Isotopes are defined as atoms of the same element that have the same $Atomic \ number$ $(Z)$ but different $Mass \ number$ $(A)$.

(B) Atoms of different elements having different atomic numbers but the same mass number are called isobars.

(B) Isotopes are atoms of the same element having the same atomic number but different mass numbers.
Nuclear charge $+6$ corresponds to an atomic number $(Z)$ of $6$,which is the element carbon.
Therefore,an atom with atomic weight $14$ and atomic number $6$ is an isotope of carbon,denoted as $_6C^{14}$.

(A) Isotopes are atoms of the same element having the same atomic number but different mass numbers.
Since chemical properties depend on the electronic configuration (which is identical for isotopes),they exhibit similar chemical properties.
However,physical properties depend on the mass of the nucleus,which differs due to the different number of neutrons,leading to different physical properties.

(A) Isotopes are defined as atoms of the same element that have the same atomic number (number of protons) but different mass numbers due to a different number of neutrons.

(C) . Isobars are atoms of different elements that have the same mass number but different atomic numbers.
In the pair $_{19}^{40}K$ and $_{20}^{40}Ca$,both have a mass number of $40$ but different atomic numbers ($19$ and $20$ respectively). Thus,they are isobars.

(A) The correct answer is $A$.
In nature,chlorine exists as two isotopes $Cl^{35}$ and $Cl^{37}$ in the ratio of $3 : 1$.
Therefore,the statement that the ratio is $1 : 3$ is false.

(D) Isobars are atoms of different elements that have the same mass number $(A)$ but different atomic numbers $(Z)$.
Since the mass number $A = Z + N$ (where $Z$ is the number of protons and $N$ is the number of neutrons),if $A$ is constant but $Z$ is different,then $N$ must also be different.
Therefore,isobars have different numbers of both protons $(p^+)$ and neutrons $(n^0)$.

(A) Atoms of different elements having different atomic numbers but the same mass number are called isobars.
Since $_{20}X^{40}$ and $_{21}X^{40}$ have different atomic numbers ($20$ and $21$) but the same mass number $(40)$,they are isobars.

(C) Isotopes are atoms of the same element that have the same atomic number (number of protons) but different mass numbers due to a different number of neutrons.
Therefore,the property that differs for neutral atoms of the two isotopes of the same element is the number of neutrons.

(C) Isotones are species that have the same number of neutrons but different atomic numbers.
For $_{37}Rb^{86}$,the number of neutrons is $N = A - Z = 86 - 37 = 49$.
Now,let us calculate the number of neutrons for each option:
$A) _{36}Kr^{84}: N = 84 - 36 = 48$
$B) _{37}Rb^{85}: N = 85 - 37 = 48$
$C) _{38}Sr^{87}: N = 87 - 38 = 49$
$D) _{39}Y^{89}: N = 89 - 39 = 50$
Since $_{38}Sr^{87}$ has $49$ neutrons,it is isotonic with $_{37}Rb^{86}$.

(C) Isotopes are atoms of the same element having the same atomic number but different mass numbers.
For $_{17}Cl^{35}$,the number of neutrons = $35 - 17 = 18$.
For $_{17}Cl^{37}$,the number of neutrons = $37 - 17 = 20$.
Therefore,the difference lies in the number of neutrons.

(B) Isotones are atoms that have the same number of neutrons $(n = A - Z)$.
For option $A$: $_{19}^{40}K$ has $40 - 19 = 21$ neutrons,$_{20}^{40}Ca$ has $40 - 20 = 20$ neutrons.
For option $B$: $_{19}^{39}K$ has $39 - 19 = 20$ neutrons,$_{20}^{40}Ca$ has $40 - 20 = 20$ neutrons.
Since both species in option $B$ have $20$ neutrons,they form an isotonic pair.

(B) The atomic number $(Z)$ of bromine is $35$. The two isotopes of bromine are $_{35}Br^{79}$ and $_{35}Br^{81}$.
The number of neutrons is calculated using the formula: $\text{Neutrons} = \text{Mass number} (A) - \text{Atomic number} (Z)$.
For the first isotope $(_{35}Br^{79})$: $\text{Neutrons} = 79 - 35 = 44$.
For the second isotope $(_{35}Br^{81})$: $\text{Neutrons} = 81 - 35 = 46$.
Thus,the correct number of neutrons is $44$ and $46$.

(D) . Isotopes are atoms of the same element that have the same atomic number but different mass numbers. Because they have the same number of electrons,they exhibit the same chemical properties.

(A) Isotopes are atoms of the same element that have the same atomic number but different mass numbers due to a different number of neutrons in their nuclei.
Since the atomic number is the same,the number of electrons in neutral atoms is also the same,leading to identical chemical properties.
Therefore,the property that differs is the mass.

(C) The addition of neutrons to an atom changes its mass number but does not change its atomic number $(Z)$.
Since the atomic number remains the same,the chemical properties remain unchanged.
Atoms with the same atomic number but different mass numbers are called isotopes.
Therefore,the reaction is: $_Z{A^m} + 2\,_0n^1 \to \,_Z{A^{m+2}}$,which represents an isotope of $A$.

(A) Isotopes are defined as atoms of the same element that have the same atomic number $(Z)$ but different mass numbers $(A)$.
Since the atomic number is the same,the number of protons and electrons remains identical.
Therefore,the character that differs is the atomic mass.

(A) The symbol of an isotope is represented as $_{Z}X^{A}$,where $Z$ is the atomic number and $A$ is the mass number (atomic weight).
In the given symbol $_{32}X^{65}$,the atomic number $(Z)$ is $32$ and the mass number $(A)$ is $65$.
Therefore,the correct statement is that its atomic number is $32$ and atomic weight is $65$.

(B) Atoms of different elements having different atomic numbers but the same mass number are known as isobars.

(C) The atoms of different elements having different atomic numbers but the same mass number are called isobars.
In the given species,the atomic numbers are $18$,$20$,and $19$ respectively,while the mass number for all is $40$.
Therefore,they are isobars.

(D) Isotopes are defined as atoms of the same element that have the same atomic number (number of protons) but different mass numbers due to a different number of neutrons.
Therefore,all isotopes of oxygen must have the same number of protons ($8$ protons for oxygen).