Question 11 Mark
How many electrons in an atom may have the following quantum numbers?
n = 3, l = 0.
Answern = 3 and l = 0 means it is 3s orbital which can have only 2 electrons.
View full question & answer→Question 21 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=1, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$
AnswerThe given set of quantum numbers is not possible.
For a given value of n, ‘l’ can have values from zero to (n – 1).
For n = 1, l = 0 and not 1.
View full question & answer→Question 31 Mark
Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 4; l = 3.
AnswerFor n = 4 and l = 3
The orbital is 4f.
View full question & answer→Question 41 Mark
Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
3d and 3p.
AnswerNuclear charge is defined as the net positive charge experienced by an electron in the orbital of a multi-electron atom. The closer the orbital, the greater is the nuclear charge experienced by the electron (s) in it.
3p will experience greater nuclear charge since it is closer to the nucleus than 3f.
View full question & answer→Question 51 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=3, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$
AnswerThe given set of quantum numbers is possible.
View full question & answer→Question 61 Mark
Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 4; l = 2.
AnswerFor n = 4 and l = 2
The orbital is 4d.
View full question & answer→Question 71 Mark
Calculate the total number of electrons present in one mole of methane.
AnswerElectrons present in 1 molecule of methane $\left(\mathrm{CH}_4\right)=6+4=10$
$\therefore$ Electrons in mol i.e. $6.022 \times 10^{23}$ molecules $=6.022 \times 10^{24}$
View full question & answer→Question 81 Mark
How many subshells are associated with n = 4?
Answern = 4 (Given)
For a given value of ‘n’, ‘l’ can have values from zero to (n – 1).
$\therefore$ l = 0, 1, 2, 3
Thus, four sub-shells are associated with n = 4, which are s, p, d and f.
View full question & answer→Question 91 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=0, \text{l}=0,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$
AnswerThe given set of quantum numbers is not possible because the value of the principal quantum number (n) cannot be zero.
View full question & answer→Question 101 Mark
List the quantum numbers ( $m_l $ and I) of electrons for 3d orbital.
AnswerFor 3 d orbital, $\mathrm{n}=3, \mathrm{I}=2$.
$\therefore$ For $I=2$
$m_2=-2,-1,0,1,2$
View full question & answer→Question 111 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=1, \text{l}=0,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=-\frac{1}{2}$
AnswerThe given set of quantum numbers is possible.
View full question & answer→Question 121 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=3, \text{l}=3,\text{m}_{\text{l}}=-3,\text{m}_{\text{s}}=+\frac{1}{2}$
AnswerThe given set of quantum numbers is not possible.
For n = 3,
l = 0 to (3 – 1)
l = 0 to 2 i.e., 0, 1, 2
View full question & answer→Question 131 Mark
How many electrons in an atom may have the following quantum numbers?
$\text{n}=4,\text{m}_{\text{s}}=-\frac{1}{2}$
AnswerThe total number of electrons in $n$ is given by $2 \mathrm{n}^2$
$n=4$, Number of electrons $=2 \times 4^2=32$
Half of 32 electrons will have spin quantum number $\mathrm{m}_{\mathrm{s}}=-\frac{1}{2}$ i.e. 16 electrons
View full question & answer→Question 141 Mark
Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
4d and 4f.
AnswerNuclear charge is defined as the net positive charge experienced by an electron in the orbital of a multi-electron atom. The closer the orbital, the greater is the nuclear charge experienced by the electron (s) in it.4d will experience greater nuclear charge than 4f since 4d is closer to the nucleus.
View full question & answer→Question 151 Mark
Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 1; l = 0.
Answern = 1, l = 0 (Given)
The orbital is 1s.
View full question & answer→Question 161 Mark
Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 17 , A = 35.
Answer$\text{ }^{35}_{17}\text{Cl}$
View full question & answer→Question 171 Mark
Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 3; l = 1.
AnswerFor n = 3 and l = 1
The orbital is 3p.
View full question & answer→Question 181 Mark
Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 92 , A = 233.
Answer$\text{ }^{233}_{92}\text{U}$
View full question & answer→Question 191 Mark
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=2, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=-\frac{1}{2}$
AnswerThe given set of quantum numbers is possible.
View full question & answer→Question 201 Mark
Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 4 , A = 9.
Answer$\text{ }^{9}_{4}\text{Be}$
View full question & answer→Question 211 Mark
Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
2s and 3s,
AnswerNuclear charge is defined as the net positive charge experienced by an electron in the orbital of a multi-electron atom. The closer the orbital, the greater is the nuclear charge experienced by the electron (s) in it.
The electron(s) present in the 2s orbital will experience greater nuclear charge (being closer to the nucleus) than the electron(s) in the 3s orbital.
View full question & answer→Question 221 Mark
Why did Heisenberg replace the concept of definite orbits by the concept of probability?
AnswerThe exact position of electron cannot be determined, therefore, the concept of orbits was replaced by the concept of probability.
View full question & answer→Question 231 Mark
Write the number of electrons present in mole of $\mathrm{N}^{3-}$ ion.
AnswerElectron presents in $1 \mathrm{~N}^{3-}$ ion $=7+3=10$ electrons.
$[\because$ At no $=\mathrm{E}=7$ for nitrogan]
1 mole of $\mathrm{N}^{3-}$ ion have $=10 \times 6.022 \times 10^{23}$ electrons,
$=6.022 \times 10^{24}$ electrons.
View full question & answer→Question 241 Mark
How many radial and angular nodes are present in 2p-orbital.
AnswerRadial node = n - l - 1 = 2 - 1 - 1 = 0,
Angular nodes = ‘l’ = 1
View full question & answer→Question 251 Mark
According to Bohr's model, $E_n$ of each stationary state is given by the expression:
$\text{E}_\text{n}=\frac{-1312}{\text{n}^2}\text{KJ}/ \text{ mol}^{-1}$
What does 'n' stand for?
Answer'n' stands for energy level.
View full question & answer→Question 261 Mark
Why Bohr's orbits are called energy levels?
AnswerIt is because they are associated with fixed amount of energy.
View full question & answer→Question 271 Mark
Write all the four quantum numbers of the electron in the outermost shell of rubidium atom. (Atomic number = 37).
Answer$\operatorname{Rb}(37): 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^6 5 s^1$
$\text{n}=5,\text{l}=0,\text{m}$ $=0,\text{s}=+\frac{1}{2}\Big(\text{either }+\frac{1}{2}\ \text{or}\ -\frac{1}{2}\Big).$
View full question & answer→Question 281 Mark
Which two discoveries put strong challenge to the Bohr model?
AnswerHeisenberg's uncertainty principle and de-Broglie's concept of dual nature of matter are two discoveries that put strong challenge to the Bohr model.
View full question & answer→Question 291 Mark
What is the difference between photon and quantum?
Answer
|
S. No
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Photon
|
Quantum
|
|
1.
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A photon is an elementary particle.
|
Quantum is not an elementary particle.
|
|
2.
|
It has both particle and wave like nature.
|
It does not have dual nature.
|
View full question & answer→Question 301 Mark
Which quantum number specifies the shape of an orbital?
AnswerAzimuthal quantum number (l) specifies the shape of an orbital.
View full question & answer→Question 311 Mark
Which quantum number determines:
- Energy of electron,
- Orientation of orbital?
Answer
- Principal quantum number(n),
- Magnetic quantum number(m).
View full question & answer→Question 321 Mark
Which of the following will not show deflection from the path on passing through an electric field?
Proton, cathode rays, electron, neutron.
AnswerNeutron, since it is neutral and cannot be deflected by an electric field.
View full question & answer→Question 331 Mark
The number of electrons, protons and neutrons in a species are equal to 18, 16 and 16 respectively. Assign the proper symbol to the species.
AnswerNumber of electrons = 18 Number of protons = 16 = Atomic number, Number of neutrons = 16 The symbol of a species is $S^{2-}$.
View full question & answer→Question 341 Mark
How are $\mathrm{d}_{\mathrm{xy}}$ and $\mathrm{d}_{\mathrm{x}^2}-\mathrm{y}^2$ orbitals related?
AnswerThe $d_{x y}$ orbital is exactly like $d_{x^2}-y^2$ orbital except that its lobes are at an angle of $45^{\circ}$ to the lobes of $\mathrm{dx}^2-\mathrm{y}^2$ orbital.
View full question & answer→Question 351 Mark
Why is following electronic configuration not correct for ground state of Cr atom?
(Atomic number $=24$ ) $1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^4$.
AnswerThe electronic configuration of $\mathrm{Cr}(24)$ in ground state is,
$1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^1 3 d^5$ because half-filled orbitals are more stable.
View full question & answer→Question 361 Mark
Why is energy of 1s electron lower than 2s electron?
AnswerIs electron is closer to nucleus than 2s, therefore, has more force of attraction.
View full question & answer→Question 371 Mark
Explain why the uncertainty principle is significant only for the motion of sub-atomic particles but is negligible for the macroscopic objects?
AnswerThe energy of photon is sufficient to disturb a sub-atomic particle so that there is uncertainty in the measurement of position and momentum of the sub-atomic particle. However, the energy is insufficient to disturb a macroscopic object.
View full question & answer→Question 381 Mark
Why do many elements have fractional atomic masses?
AnswerIt is because they have isotopes.
View full question & answer→Question 391 Mark
An element has electronic configuration $[A r] 3 d^4$ in its +3 oxidation state. What will be electronic configuration of its atom?
AnswerThe electronic configuration of its atom is:
$1 s^2\ 2 s^2\ 2 p^6\ 3 s^2\ 4 s^2\ 3 d^5 \text { or }[\operatorname{Ar}] 4 s^2\ 3 d^5$.
View full question & answer→Question 401 Mark
Why cannot the motion of an electron around the nucleus be determined accurately?
AnswerIt is because we need high energy radiations to see an electron which change the velocity of electron.
View full question & answer→Question 411 Mark
Write the possible values of 'm' for an electron with l = 1.
AnswerWhen I = 1, the possible values of m are -1, 0, +1.
View full question & answer→Question 421 Mark
Name two phenomena that indicate the dual nature of electrons.
Answer
- Photoelectric effect,
- Diffraction.
View full question & answer→Question 431 Mark
Why is 4s-orbital filled before 3d-orbital?
Answer4s-orbital has (n + l) = 4 + 0 = 4,
Which is lower than that of 3d, i.e. 3 + 2 = 5.
View full question & answer→Question 441 Mark
How many electrons in an atom have the following quantum numbers? n = 3, l = 0.
AnswerThe value of n = 3 and I = 0 implies 3s orbital. 3s orbital can have maximum of 2 electrons. Hence 2 electrons can have this set of quantum numbers.
View full question & answer→Question 451 Mark
The line spectrum of an element is known as fingerprints of its atom. Comment.
AnswerThe line spectrum of every element is unique by which it can be identified in the same manner as a person can be identified by finger prints.
View full question & answer→Question 461 Mark
What would be the colour of light emitted from an excited hydrogen atom when an electron jumps from n = 3 to n = 2?
AnswerRed colour because it is of highest wavelength and lowest energy.
View full question & answer→Question 471 Mark
What type of metals are used in photoelectric cell? Give one example.
AnswerMetals with large size with less work function e.g. Cs(cesium).
View full question & answer→Question 481 Mark
Write the electronic configuration of $\mathrm{Cr}^{+}$ion (Atomic number of $\mathrm{Cr}=24$ ).
Answer$1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^5$.
View full question & answer→Question 491 Mark
Write the values of the quantum number $\mathrm{n}, \mathrm{l}, \mathrm{m}$ and s for electron filling $21^{\text {st }}$ place in the atom of element with atomic number 24.
AnswerElectronic configuration of element,
$=1 s^2, 2 s^2, 2 p^6, 3 s^2, 3 p^6, 4 s^1, 3 d^5$
21st electron goes to 3 d -orbital. Its quantum numbers are,
$\mathrm{n}=3,1=2, \mathrm{~s}=+\frac{1}{2}$ or $-\frac{1}{2}$
m can have any value out of $-2,-1,0,+1,+2$.
View full question & answer→Question 501 Mark
Write electronic configuration of:
i. $\mathrm{Na}^{+}(11)$,
ii. $\mathrm{Cl}^{-}(17)$.
Answeri. $\mathrm{Na}^{-}(11): 1 s^2 2 s^2 2 p^6$,
ii. $\mathrm{Cl}^{-}\left(\mathbf{1 7 )}: 1 \mathrm{~s}^2 2 \mathrm{~s}^2 2 \mathrm{p}^6 3 s^2 3 \mathrm{p}^6\right.$.
View full question & answer→Question 511 Mark
What is the value of Bohr's radius for the first orbit of hydrogen atom?
Answer$\text{r}_1=0.529\mathring{\text{A}}=0.529\times10^{-10}\text{m}$
$=5.29\times10^{-11}\text{m}$
View full question & answer→Question 521 Mark
What are degenerate orbitals?
AnswerThose orbitals which have equal energy are degenerate orbitals.
View full question & answer→Question 531 Mark
What do you mean by saying that energy of the electron is quantised?
AnswerThis means that the electrons in an atom have only definite values of energies.
View full question & answer→Question 541 Mark
What is the possible value of angular momentum quantum number (l) for the unpaired electron in the atom of an element whose atomic number is 17?
Answerl = 1 for unpaired electron of Cl(17):
$1\text{s}^2\ 2\text{s}^2\ 3\text{s}^2\ 3\text{p}^2_\text{x}\ 3\text{p}^2_\text{v}\ 3\text{p}^1_\text{z}.$
View full question & answer→Question 551 Mark
In which atom, the outermost electron can have the following set of quantum numbers?) $n=3, I=0, m_l=0, m_s$ $=\frac{-1}{2}$
Answer$\mathrm{n}=3$ and $\mathrm{I}=0$ means the last electron enters in 3 s -orbital. Thus, the complete configuration upto 3 is $1 \mathrm{~s}^2, 2 \mathrm{~s}^2, 2 \mathrm{p}^6$, $3 s^1$ Total number of electrons,
$=2+2+6+1=11$. Thus, the element is sodium.
View full question & answer→Question 561 Mark
An orbital has I = 3, what are the possible values of m?
Answerl = 3; m = -3, -2, -1, 0, +1, +2, +3
View full question & answer→Question 571 Mark
What physical meaning is attributed to the square of the absolute value of wave function, $|\psi|^2?$
Answer$|\psi|^2$ shows the probability of finding the electron at a point with coordinates (x, y, z).
View full question & answer→Question 581 Mark
Write the difference between atomic mass and atomic mass number?
AnswerAtomic mass is the mass of all the sub-atomic particles present in an atom, mainly proton and neutrons as electron have negligible mass. Atomic mass number is equal to sum of number of protons and neutrons.
View full question & answer→Question 591 Mark
Write a cation and an anion which is isoelectronic with Ar. (Atomic number of Ar = 18]
Answer$\mathrm{Ca}^{2+}$ is cation and $\mathrm{Cl}^{-}$ion is ions which are isoelectronic with Ar.
View full question & answer→Question 601 Mark
Cs shows maximum photo electric effect, why?
AnswerIt is alkali metal with large size, lowest ionisation enthalpy i.e. lowest work function.
View full question & answer→Question 611 Mark
How many orbitals are present in 'g' sub-shell?
Answer9 orbitals. Because for 'g' orbital, l = 4, m = -4, -3, -2, -1, 0, +1, +2, +3, +4
9 values of 'm' means 9 type of orbitals.
View full question & answer→Question 621 Mark
How many electrons and protons are present in the anion of $\mathrm{Li}_3 \mathrm{N}$ ?
Answer$\mathrm{N}^{3-}$ is anion which has 7 protons and 10 electrons.
View full question & answer→Question 631 Mark
How does the intensity of the spectral line vary with wavelength?
AnswerAs the wavelength decreases, intensity also decreases.
View full question & answer→Question 641 Mark
$\mathrm{CI}, \mathrm{Cl}^{-}$ have same atomic number or mass number or both? Explain.
AnswerThey have same atomic number as well as mass number. It is because they differ in number of electrons but have same number of protons and neutrons. Atomic number (Z) = Number of protons, Mass number = Number of protons + Number of neutrons.
View full question & answer→Question 651 Mark
Write electronic configuration of $\mathrm{Ni}^{2+}($ Atomic number of $\mathrm{Ni}=28)$.
Answer$1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^8 .[\because$ Electrons are removed from 4s orbital first, then from 3d]
View full question & answer→Question 661 Mark
i. What is difference between 'I' and 'L'?
ii. Nitrogen has 7 protons, 7 electrons, 7 neutrons. Calculate the number of electrons, Protons and neutrons in $\mathrm{N}^{3-} ion.$
Answeri. 'I' represents azimuthul quantum number which determines shape of orbital e.g. I = 0 is sorbital (spherical)
'L' represents $2^{\text {nd }}$ shell or orbit or energy level.
ii. $\mathrm{N}^{3-}$ is formed when ' N ' atoms gains 3 electrons
Number of electrons in $\mathrm{N}^{3-}=7+3=10$ electrons
Proton in $\mathrm{N}^{3-}=7$
Neutrons in $\mathrm{N}^{3-}=7$
View full question & answer→Question 671 Mark
Which one of the atomic orbital has higher energy?
- n = 3,1 = 2, m = +1,
- n = 4, 1 = 0, m = 0.
Answer
- 3d has higher energy,
- 4s orbital.
View full question & answer→Question 681 Mark
How does change in velocity of a moving particle alter the wavelength of the particle?
Answer$'\lambda'$ (wavelength) decreases with increase in velocity of moving particle, i.e $\lambda=\frac{\text{h}}{\text{mV}}.$
View full question & answer→Question 691 Mark
The electronic configuration of N (7) is $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z}$ and not $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^2_\text{x}\ 2\text{p}^1_\text{y}.$Why?
AnswerN(7) has electronic configuration $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z}$ and not $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^2_\text{x}\ 2\text{p}^1_\text{y},$ because latter violates Hund's rule which states degenerate (having equal energy) orbitals are first singly filled and then pairing starts so as to avoid repulsion.
View full question & answer→Question 701 Mark
Write electronic configuration of $\mathrm{Cu}^{2+}(29), \mathrm{Cr}^{3+}(24)$.
Answer$\mathbf{C u}^{2+}(\mathbf{2 9}): 1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^9$
$\mathbf{C r}^{3+}(24): 1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^3$
View full question & answer→Question 711 Mark
An electron is in one of the 3 d-orbitals. Give the possible values of n, I and m, for this electron.
AnswerFor 3d electron, n = 3, 1 = 2, m = -2, - 1, 0, +1, + 2
View full question & answer→Question 721 Mark
Which series of hydrogen spectrum lies in:
- Visible region,
- UV region?
Answer
- Balmer series,
- Lyman series.
View full question & answer→Question 731 Mark
Give the value of n and I for 2s orbital.
Answern = 2, l = 0 for 2s orbital.
View full question & answer→Question 741 Mark
How many electrons are present in $\text{NO}^-_3?$
Answer$\text{NO}^-_3$ ion has 7 + 8 3 + 1 = 7 + 24 + 1 = 32 electrons.
View full question & answer→Question 751 Mark
Neutron or proton of same wavelength, which will have more velocity?
AnswerProton will have more velocity due to smaller mass.
View full question & answer→Question 761 Mark
How many unpaired electrons are present in N(7)? Name the principle which explains the presence of these unpaired electrons.
Answer$\text{N}(7):1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z},$ there are 3 unpaired electrons due to Hund's rule.
View full question & answer→Question 771 Mark
Name the element whose isotope has mass number 14 and having 8 neutrons.
AnswerAtomic number = Mass number - Number of neutrons,
Atomic number = 14 - 8 = 6, so the element is carbon.
View full question & answer→Question 781 Mark
What happens to the position and momentum of an electron if a photon of a short wavelength hits the electron?
AnswerThe uncertainty in position decreases but the uncertainty in velocity or momentum increases if the wavelength of photon is short.
View full question & answer→Question 791 Mark
Which quantum number is not derived from Schrodinger wave equation?
Question 801 Mark
What is the difference between a quantum and a photon?
AnswerThe smallest packet of energy of any radiation is called a quantum whereas that of light is called a photon.
View full question & answer→Question 811 Mark
How many orbitals are there in 3rd shell?
AnswerIn 3rd shell, there are nine orbitals.
View full question & answer→Question 821 Mark
Can we apply Heisenberg's uncertainty principle to a stationary electron? Why or why not?
AnswerNo, because velocity = 0 and thus, position can be measured accurately.
View full question & answer→Question 831 Mark
Why does a cannot seem to travel in the form of a wave although de-Broglie relation is applicable to it?
AnswerThis is because in this case wavelength is negligible as the mass of car is very high and wavelength is inversely proportional to mass.
View full question & answer→Question 841 Mark
Write the name of non-directional orbital.
Answers-orbital is spherically symmetrical, i.e. non-directional.
View full question & answer→Question 851 Mark
What are the values of 'n' and ‘l’ for 4f-orbital?
Answern = 4, l = 3 for 4f-orbital.
View full question & answer→Question 861 Mark
What is the difference in the angular momentum of an electron present in 3p and 4p orbitals?
AnswerAngular momentum ‘l’ of 3p and 4p orbitals will be same because I = 1 for p orbital.
View full question & answer→Question 871 Mark
Why is energy of electron negative?
AnswerWhen electron is at infinite distance from nucleus, its energy is zero. When it is brought near to the nucleus, energy becomes less than zero, i.e. negative due to force of attraction between nucleus and electron.
View full question & answer→Question 881 Mark
What are four quantum numbers of $19^{th}$ electron of copper?
AnswerCu(29): $1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^1 ~3 d^{10}$
n = 4, l = 0, m = 0, s $=\frac{+1}{2}$
View full question & answer→