1 Marks Question

Question 11 Mark

How many electrons in an atom may have the following quantum numbers?
n = 3, l = 0.

Answer

n = 3 and l = 0 means it is 3s orbital which can have only 2 electrons.

Question 21 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=1, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$

Answer

The 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.

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Question 31 Mark

Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 1; l = 0.

Answer

n = 1, l = 0 (Given)
The orbital is 1s.

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Question 41 Mark

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
4d and 4f.

Answer

4d will experience greater nuclear charge than 4f since 4d is closer to the nucleus.

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Question 51 Mark

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 4 , A = 9.

Answer

$\text{ }^{9}_{4}\text{Be}$

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Question 61 Mark

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
2s and 3s,

Answer

Nuclear 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.

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Question 71 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=3, \text{l}=3,\text{m}_{\text{l}}=-3,\text{m}_{\text{s}}=+\frac{1}{2}$

Answer

The 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

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Question 81 Mark

Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 3; l = 1.

Answer

For n = 3 and l = 1
The orbital is 3p.

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Question 91 Mark

How many electrons in an atom may have the following quantum numbers?
$\text{n}=4,\text{m}_{\text{s}}=-\frac{1}{2}$

Answer

The total number of electrons in n is given by 2n²
n = 4, Number of electrons = 2 × 4²= 32
Half of 32 electrons will have spin quantum number $\text{m}_{\text{s}}=-\frac{1}{2}$ i.e. 16 electrons

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Question 101 Mark

Calculate the total number of electrons present in one mole of methane.

Answer

Electrons present in 1 molecule of methane (CH₄) = 6 + 4 = 10
$\therefore$ Electrons in mol i.e. 6.022 × 10²³ molecules = 6.022 × 10²⁴

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Question 111 Mark

How many subshells are associated with n = 4?

Answer

n = 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.

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Question 121 Mark

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 17 , A = 35.

Answer

$\text{ }^{35}_{17}\text{Cl}$

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Question 131 Mark

List the quantum numbers (m_l and l ) of electrons for 3d orbital.

Answer

For 3d orbital, n = 3, l = 2.
$\therefore$ For l = 2
m₂ = -2, -1, 0, 1, 2

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Question 141 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=2, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=-\frac{1}{2}$

Answer

The given set of quantum numbers is possible.

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Question 151 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=1, \text{l}=0,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=-\frac{1}{2}$

Answer

The given set of quantum numbers is possible.

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Question 161 Mark

Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 4; l = 3.

Answer

For n = 4 and l = 3
The orbital is 4f.

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Question 171 Mark

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge?
3d and 3p.

Answer

Nuclear 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.

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Question 181 Mark

Using s, p, d notations, describe the orbital with the following quantum numbers.
n = 4; l = 2.

Answer

For n = 4 and l = 2
The orbital is 4d.

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Question 191 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=0, \text{l}=0,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$

Answer

The given set of quantum numbers is not possible because the value of the principal quantum number (n) cannot be zero.

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Question 201 Mark

Explain, giving reasons, which of the following sets of quantum numbers are not possible.
$\text{n}=3, \text{l}=1,\text{m}_{\text{l}}=0,\text{m}_{\text{s}}=+\frac{1}{2}$

Answer

The given set of quantum numbers is possible.

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Question 211 Mark

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A),
Z = 92 , A = 233.

Answer

$\text{ }^{233}_{92}\text{U}$

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Question 221 Mark

Write the difference between atomic mass and atomic mass number?

Answer

Atomic 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.

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Question 231 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.

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Question 241 Mark

Write electronic configuration of Cu²⁺(29), Cr³⁺(24).

Answer

Cu²⁺(29): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s⁰ 3d⁹,
Cr³⁺(24): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s⁰ 3d³.

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Question 251 Mark

Write electronic configuration of Ni²⁺(Atomic number of Ni = 28).

Answer

1s² 2s² 2p⁶ 3s² 3p⁶ 4s⁰ 3d⁸. $[\because$ Electrons are removed from 4s orbital first, then from 3d$]$

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Question 261 Mark

Neutron or proton of same wavelength, which will have more velocity?

Answer

Proton will have more velocity due to smaller mass.

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Question 271 Mark

Name the element whose isotope has mass number 14 and having 8 neutrons.

Answer

Atomic number = Mass number - Number of neutrons,
Atomic number = 14 - 8 = 6, so the element is carbon.

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Question 281 Mark

Why did Heisenberg replace the concept of definite orbits by the concept of probability?

Answer

The exact position of electron cannot be determined, therefore, the concept of orbits was replaced by the concept of probability.

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Question 291 Mark

Why do many elements have fractional atomic masses?

Answer

It is because they have isotopes.

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Question 301 Mark

How are d_xy and d_x² – y² orbitals related?

Answer

The d_xy orbital is exactly like d_x² - y² orbital except that its lobes are at an angle of 45° to the lobes of d_x² - y² orbital.

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Question 311 Mark

What are four quantum numbers of 19^th electron of copper?

Answer

Cu(29): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
n = 4, l = 0, m = 0, s $=\frac{+1}{2}$

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Question 321 Mark

What is difference between 'l' and 'L'?
Nitrogen has 7 protons, 7 electrons, 7 neutrons. Calculate the number of electrons, Protons and neutrons in N^3-ion.

Answer

‘l’ represents azimuthul quantum number which determines shape of orbital e.g. l = 0 is s-orbital (spherical)

'L' represents 2^nd shell or orbit or energy level.

N^3- is formed when ‘N’ atoms gains 3 electrons

Number of electrons in N^3- = 7 + 3 = 10 electrons

Proton in N^3- = 7

Neutrons in N^3- = 7

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Question 331 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.

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Question 341 Mark

Write the number of electrons present in mole of N^3- ion.

Answer

Electron presents in 1N^3- ion = 7 + 3 = 10 electrons.
$[\because$ At no = E = 7 for nitrogan$]$
1 mole of N^3- ion have = 10 × 6.022 × 10²³ electrons,
= 6.022 × 10²⁴ electrons.

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Question 351 Mark

What type of metals are used in photoelectric cell? Give one example.

Answer

Metals with large size with less work function e.g. Cs(cesium).

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Question 361 Mark

Write the electronic configuration of Cr⁺ ion (Atomic number of Cr = 24).

Answer

1s² 2s² 2p⁶ 3s² 3p⁶ 4s⁰ 3d⁵.

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Question 371 Mark

Write the values of the quantum number n, l, m and s for electron filling 21^st place in the atom of element with atomic number 24.

Answer

Electronic configuration of element,
= 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁵
21st electron goes to 3d-orbital. Its quantum numbers are,
$\text{n}=3,\text{l}=2,\text{s}=+\frac{1}{2}\ \text{or }-\frac{1}{2}$
m can have any value out of -2, -1, 0, +1, + 2.

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Question 381 Mark

Why Bohr's orbits are called energy levels?

Answer

It is because they are associated with fixed amount of energy.

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Question 391 Mark

Write all the four quantum numbers of the electron in the outermost shell of rubidium atom. (Atomic number = 37).

Answer

Rb(37): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹;
$\text{n}=5,\text{l}=0,\text{m}$
$=0,\text{s}=+\frac{1}{2}\Big(\text{either }+\frac{1}{2}\ \text{or}\ -\frac{1}{2}\Big).$

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Question 401 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 $\lambda=\frac{\text{h}}{\text{mV}}.$

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Question 411 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?

Answer

N(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.

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Question 421 Mark

What is the difference in the angular momentum of an electron present in 3p and 4p orbitals?

Answer

Angular momentum ‘l’ of 3p and 4p orbitals will be same because I = 1 for p orbital.

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Question 431 Mark

Which two discoveries put strong challenge to the Bohr model?

Answer

Heisenberg's uncertainty principle and de-Broglie's concept of dual nature of matter are two discoveries that put strong challenge to the Bohr model.

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Question 441 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

n = 3 and l = 0 means the last electron enters in 3s-orbital. Thus, the complete configuration upto 3 is 1s², 2s², 2p⁶, 3s¹ Total number of electrons,
= 2 + 2 + 6 + 1 = 11. Thus, the element is sodium.

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Question 451 Mark

An orbital has I = 3, what are the possible values of m?

Answer

l = 3; m = -3, -2, -1, 0, +1, +2, +3

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Question 461 Mark

Which quantum number specifies the shape of an orbital?

Answer

Azimuthal quantum number (l) specifies the shape of an orbital.

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Question 471 Mark

An element has electronic configuration [Ar] 3d⁴in its +3 oxidation state. What will be electronic configuration of its atom?

Answer

The electronic configuration of its atom is:
1s² 2s² 2p⁶ 3s² 4s² 3d⁵ or [Ar] 4s² 3d⁵.

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Question 481 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).

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Question 491 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?

Answer

l = 1 for unpaired electron of Cl(17):
$1\text{s}^2\ 2\text{s}^2\ 3\text{s}^2\ 3\text{p}^2_\text{x}\ 3\text{p}^2_\text{v}\ 3\text{p}^1_\text{z}.$

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Question 501 Mark

An electron is in one of the 3 d-orbitals. Give the possible values of n, I and m, for this electron.

Answer

For 3d electron, n = 3, 1 = 2, m = -2, - 1, 0, +1, + 2

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Question 511 Mark

What would be the colour of light emitted from an excited hydrogen atom when an electron jumps from n = 3 to n = 2?

Answer

Red colour because it is of highest wavelength and lowest energy.

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Question 521 Mark

Why is energy of 1s electron lower than 2s electron?

Answer

Is electron is closer to nucleus than 2s, therefore, has more force of attraction.

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Question 531 Mark

What happens to the position and momentum of an electron if a photon of a short wavelength hits the electron?

Answer

The uncertainty in position decreases but the uncertainty in velocity or momentum increases if the wavelength of photon is short.

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Question 541 Mark

Write the possible values of 'm' for an electron with l = 1.

Answer

When I = 1, the possible values of m are -1, 0, +1.

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Question 551 Mark

Write the name of non-directional orbital.

Answer

s-orbital is spherically symmetrical, i.e. non-directional.

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Question 561 Mark

Which quantum number is not derived from Schrodinger wave equation?

Answer

Spin quantum number.

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Question 571 Mark

How many radial and angular nodes are present in 2p-orbital.

Answer

Radial node = n - l - 1 = 2 - 1 - 1 = 0,
Angular nodes = ‘l’ = 1

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Question 581 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.

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Question 591 Mark

Why is 4s-orbital filled before 3d-orbital?

Answer

4s-orbital has (n + l) = 4 + 0 = 4,
Which is lower than that of 3d, i.e. 3 + 2 = 5.

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Question 601 Mark

Why does a cannot seem to travel in the form of a wave although de-Broglie relation is applicable to it?

Answer

This is because in this case wavelength is negligible as the mass of car is very high and wavelength is inversely proportional to mass.

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Question 611 Mark

How does the intensity of the spectral line vary with wavelength?

Answer

As the wavelength decreases, intensity also decreases.

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Question 621 Mark

Which of the following will not show deflection from the path on passing through an electric field?
Proton, cathode rays, electron, neutron.

Answer

Neutron, since it is neutral and cannot be deflected by an electric field.

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Question 631 Mark

CI, Cl^- have same atomic number or mass number or both? Explain.

Answer

They 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.

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Question 641 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.

Answer

Number of electrons = 18
Number of protons = 16 = Atomic number,
Number of neutrons = 16
The symbol of a species is S^2-.

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Question 651 Mark

Why cannot the motion of an electron around the nucleus be determined accurately?

Answer

It is because we need high energy radiations to see an electron which change the velocity of electron.

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Question 661 Mark

What is the value of Bohr's radius for the first orbit of hydrogen atom?

Answer

$\text{r}_1=0.529\mathring{\text{A}}=0.529\times10^{-10}\text{m}$
$=5.29\times10^{-11}\text{m}$

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Question 671 Mark

Can we apply Heisenberg's uncertainty principle to a stationary electron? Why or why not?

Answer

No, because velocity = 0 and thus, position can be measured accurately.

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Question 681 Mark

How many electrons and protons are present in the anion of Li₃N?

Answer

N^3- is anion which has 7 protons and 10 electrons.

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Question 691 Mark

Why is energy of electron negative?

Answer

When 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.

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Question 701 Mark

Give the value of n and I for 2s orbital.

Answer

n = 2, l = 0 for 2s orbital.

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Question 711 Mark

Write a cation and an anion which is isoelectronic with Ar. (Atomic number of Ar = 18]

Answer

Ca²⁺ is cation and Cl^- ion is ions which are isoelectronic with Ar.

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Question 721 Mark

Cs shows maximum photo electric effect, why?

Answer

It is alkali metal with large size, lowest ionisation enthalpy i.e. lowest work function.

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Question 731 Mark

Explain why the uncertainty principle is significant only for the motion of sub-atomic particles but is negligible for the macroscopic objects?

Answer

The 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.

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Question 741 Mark

How many electrons in an atom have the following quantum numbers? n = 3, l = 0.

Answer

The 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.

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Question 751 Mark

How many orbitals are present in 'g' sub-shell?

Answer

9 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.

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Question 761 Mark

What is the difference between a quantum and a photon?

Answer

The smallest packet of energy of any radiation is called a quantum whereas that of light is called a photon.

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Question 771 Mark

The line spectrum of an element is known as fingerprints of its atom. Comment.

Answer

The 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.

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Question 781 Mark

How many orbitals are there in 3rd shell?

Answer

In 3rd shell, there are nine orbitals.

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Question 791 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.

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Question 801 Mark

Write electronic configuration of:

Na⁺(11),
Cl^-(17).

Answer

Na^-(11): 1s² 2s² 2p⁶,
Cl^-(17): 1s² 2s² 2p⁶ 3s² 3p⁶.

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Question 811 Mark

What is the difference between photon and quantum?

Answer

S. No	Photon	Quantum
1.	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.