S.S.C CLASS 10TH Q&A
ATOMIC STRUCTURE
ATOMIC STRUCTURE
PART - A
SECTION - I
Short Answer Questions (2 Marks Each)
1. Explain why electrons enter into '4s' orbital but not '3d' after filling '3p' orbital?
1.A The (n + l) value of 4s energy level is 4 + 0 = 4
The (n + l) value of 3d energy level is 3 + 2 = 5
According to Aufbau principle, the electron enter into the orbital having least (n + l)
value. The (n + l) value of 4s is less than 3d. Hence the electrons enter into 4s orbital
but not 3d after filling 3p orbital.
2. Write the electronic configuration of (a) Nitrogen (b) Chromium (c) Copper?
2.A (a) electronic configuration of Nitrogen is
N = Z = 7 = 1s22s22p3
(b) electronic configuration of Chromium is
Cr = Z = 24 = [Ar] 4s13d5
(c) electronic configuration of Copper is
Cu = Z = 29 = [Ar] 4s13d10
3. Distinguish between orbit and orbital?
ORBIT ORBITAL
1. The path of electron around the The region in space where there is
nucleus is called "orbit". finite probability of finding electron is
called "orbital".
2. It is two dimensional. It is three dimensional.
3. its shape is circular. It has spherical or dumb-bell or
double dumb-bell shapes.
4. The maximum number of The maximum number of electrons
electrons is 2n2. is 2.
4. Write a short notes on Quantum theory of radiation?
4.A (1) Max Planck proposed "Quantum theory of radiation", to explain the absorption
(or) emission of electromagnetic radiation.
(2) The energy is emitted (or) absorbed in the form of small packets called 'Quanta'.
(3) Energy of radiation is directly proportional to its frequency. E ∝ í.
(4) The Planck's equation is E = h
Where, E = energy of radiation
h = Planck's constant
í = frequency of radiation
5. Distinguish between Principal Quantum number and sub-level Quantum number?
5.A
Principal Quantum Number Sub-level Quantum Number
1. Proposed by Neils Bohr. Proposed by Sommerfeld.
2. Denoted by 'n'. Denoted by 'l'.
3. It indicates size and energy of a It indicates the shape of the
stationary orbit. sub-shell.
4. Its values are 1, 2, 3, 4..... (or) Its values are 0, 1, 2, 3...... and
K, L, M, N...... designated by s, p, d, f.......
5. It gives the number of the orbit It depends on 'n' value l = 0 to
(or) shell. (n – 1).
SECTION - II
Very Short Answer Questions (1 Mark Each)
1. What is Planck's Quantum equation? and what is the value of Planck's constant?
1.A Planck's Quantum equation is E = hí
Where E is Energy of radiation.
í is the frequency of radiation.
h is the Planck's constant.
The value of Planck's constant is h = 6.625 × 10–27 erg.sec.
(or) h = 6.625 × 10–34 J.sec.
2. What is a stationary orbit?
2.A Stationary orbit: Electrons are moving with high velocity around the nucleus in
specified paths called "orbits" (or) "shells". The energy of the electron in a particular
orbit is constant. Hence these orbits are called "stationary orbits".
3. What are degenerate orbitals?
3.A Degenerate orbitals: Orbitals having the same energy are called "degenerate
orbitals".
4. Who proposed the principal Quantum number?
4.A Neils Bohr proposed the principal Quantum number.
5. What are the limits of azimuthal Quantum number for a given 'n'?
5.A The limits of Azimuthal Quantum number for given n are 0 and (n – 1).
6. What are upper and lower limits of m for l = 4?
6.A. For l = 4, the upper limit is +4 and,
the lower limit is –4.
7. How many 'm' values are possible for l = 3?
7.A The magnetic Quantum number m has (2l + 1) values.
If l = 3 ; m has (2 × 3 + 1) = 7 values.
seven values are possible for l = 3
They are –3, –2, –1, 0, +1, +2, +3
8. What is the shape of '1s' orbital?
8.A Shape of '1s' orbital is symmetrically spherical.
9. What is nodal plane?
9.A Nodal Plane: The region or space around the nucleus where the probability of finding
the electron is zero is called "nodal plane" or "nodal region".
10. Write the designations of any two d-orbitals?
10.A d-orbital has five degenerate orbitals. They are designated as
11. How are the three p-orbitals designated?
11.A The three p-orbitals are designated as px, py, pz.
12. What is the unit of electron affinity?
12.A The units of electron affinity are electron volts.
xy yz zx x2 y2 z2
d ,d ,d ,d ,d
−
SECTION - III
Long Answer Questions (4 Marks Each)
1. State The Postulates of Bohr's model. What are the defects of Bohr's model?
1.A Postulates of Bohr's Atomic Model are:
Bohr proposed the model of the atom based on Planck's Quantum theory.
1. Electrons are moving around the nucleus in specified paths called "orbits". As
the energy of the electron remains constant in a particular orbit, these are called
as "stationary orbits".
2. The stationary orbits are designated by K, L, M, N......
The orbit close to the nucleus has less energy.
3. When an electron jumps from a higher energy orbit to a lower energy orbit. The
difference in the energy is emitted as radiation".
E2 – E1 = hí
E2 and E1 are energies of higher and lower orbits.
í is the frequency orbits of radiation.
h is the Planck's constant.
4. The angular momentum of the electron revolving in a stationary orbit is equal to
integral multiples of h/2ð ie.
Angular momentum,
Where, m = mass of an electron.
v = velocity of an electron.
r = radians of stationary orbit.
n = an integar n = 1, 2, 3.
h = Planck's constant.
Defects of Bohr's Model:
Bohr's atomic model could not explain.
(1) The atomic spectra of higher elements like He, Li, Be, B, C ....... which have
more than an electron.
(2) The spectral lines in presence of magnetic and electric field.
(3) The Quantization of angular momentum.
(4) The formation of chemical bonds.
2. Explain the important features of Rutherford's model of atom. Discuss its draw-backs?
2.A Rutherford's Planetary Atomic Model:
1. Rutherford proposed an atomic model in 1911, based on á-ray scattering
experiments. This is called "Planetary model" (or) "Nuclear model".
2. Atoms are spherical in shape and mostly hollow.
3. The mass of the atom is due to its nucleus. The nucleus is made up of protons
and neutrons.
4. Electrons revolve round the nucleus, just like planets revolve around the sun.
5. Two types of forces are present in the atom.
(a) The force of attraction between electrons and nucleus. It pulls the electrons
towards the nucleus.
(b) The revolving electrons experience a centrifugal force directed away from the
moving path of electrons.
h
mvr n
2
=
ð
It pulls the electrons away from the nucleus.
6. These two forces are equal and opposite. So atom is stable.
Defects of Rutherford's Model:
1. According to classical laws of physics, a moving particle should lose energy and
come closer to the nucleus.
2. If it loses energy, it eventually should fall into the nucleus and the atom should
collapse. But atoms are stable.
3. If the electron loses energy continuously, the atomic spectra should consist of
continuous bands. But atomic spectra are made up of discrete spectral lines.
3. State and explain with one example The Hund's rule of maximum multiplicity?
3.A. Hund's Rule:
1. It states that "electron pairing takes place only after all the available degenerate
orbitals are occupied by one electron each".
Eg: Consider carbon atom = Z = 6 = (1s2 2s2 2p2). It has six electrons. The first
electron enters into '1s' orbital of K-shell. The second electron will be paired up
with the first in the same '1s' orbital. The third and fourth electrons occupy the
'2s' orbital of L-shell.
The fifth electron goes into one of the three 2p orbitals of the L-shell. Let it be
2px. Since the three p orbitals (px, py, pz) are degenerate, sixth electron goes into
2py (or) 2pz but not 2px. Thus the electronic configuration of carbon is
4. Define the ionization energy and mention the factors that influence it?
4.A Ionization Energy:
"The minimum energy required to remove an electron from the outermost orbital of an
atom in gaseous state".
It depends on
i) nuclear charge
ii) size of the atom
iii) charge on the ion
iv) electronic configuration
i) Nuclear Charge: As the nuclear charge increases the ionization energy increases.
This is due to increase in the attraction of the nucleus over the valence electrons.
ii) Size of the atom: As the size of the atom increases the ionization energy
decreases. This is due to decrease in the attarction power of nucleus over the valence
electrons.
iii) Charge on the ion: As the change decreases as the energy required to remove
an electron from a cation is more than the energy required to remove from a neutral
atom.
1s2 2s2 2px
1 2py
1
iv) Electronic Configuration: Atoms with stable electronic configuration possess
high ionization potential values.
5. Explain the four Quantum numbers briefly?
5.A 1. Principal Quantum Numbers:
1. It was proposed by Neil's Bohr
2. It is denoted by the letter 'n'
3. It indicates the size and energy of a stationary orbit
4. Its values are 1, 2, 3, 4...... and these are designated as K, L, M, N......
2. Azimuthal Quantum Number:
1. It was proposed by Sommerfeld.
2. It is denoted by the letter 'l'.
3. It indicates the shape of the sub-shell.
4. Its values are 0, 1, 2, 3, 4...... and these are designated as s, p, d, f, g etc.,
3. Magnetic Quantum Number:
1. It was proposed by Lande.
2. It is denoted by the letter 'm'.
3. It indicates the orientation of the orbitals in the presence of magnetic field.
4. Its values depends on the value of 'l'.
5. For a given 'l', m can have (2l +1) values.
4. Spin Quantum Number:
1. It was proposed by Uhlenbeck and Goldsmith.
2. It is denoted by the letter 's'.
3. It indicates the direction of spin of electrons.
4. Its values are
6. State and explain Pauli's exclusion principle with example?
6.A Pauli's Exclusion Principle:
1. "No two electrons will have all the four Quantum numbers the same".
2. Eg: Atomic number of Helium (He) is = Z = 2. So the electronic configuration 1s2.
3. The Quantum numbers of the two electrons in Helium are:
n l m s
1st electron 1 0 0 +1/2
2nd electron 1 0 0 –1/2
4. For the two electrons though the first three Quantum numbers are the same,
but the fourth Quantum number differs.
7. Discuss the features of modern atomic structure?
7.A The modern concepts of atomic structure are as follows:
1. Atom consists of several stationary states or stationary orbits. These states are
designated by 'n' values.
2. Each stationary state is divided into sub-states. These sub-states are called sub-
1 1
and
2 2
+ −
energy levels and are designated by 'l' values.
3. The first stationary state n = 1 has only one sub-state, the second has two and
third has three etc. These sub-states are designated as s, p, d, f, g etc.
Corresponding to l = 0, 1, 2, 3, 4 etc.,
4. Under the influence of magnetic field, these sub-states are further split into
groups of states.
5. The electrons are placed in the sub-levels. They revolve around the nucleus and
in addition rotate on their own areas clock-wise or anti-clock wise.
SECTION - IV
DIAGRAMS (5 Marks Each)
1. Draw the shapes of s and p orbitals?
2. Draw the shapes of five 'd' orbitals?
3. Draw the diagram showing the sequence of filling of various atomic orbitals?
3.A Moeller's diagram
Increasing order of energy orbitals
1s < 2s < 2p < 3s < 3p < 4s
<3d <4p <5s <4d
<5p <6s <4f <5d <6p
<7s <5f <6d <7p <8s
PART - B
(1/2 Mark Each)
I. Pick up the Correct Answer:
1. Electron was discovered by
A) Rutherford
B) Sommerfeld
C) J.J. Thomson
D) Planck
2. The sub-shells present in N-shell are
A) s and d
B) s and p
C) s, p, d
D) s, p, d, f
3. The number of d-orbitals present in n = 3 is
A) 1
B) 3
C) 5
D) 7
4. The shape of p-orbitals is
A) spherical
B) dumb-bell
C) double dumb-bell
D) Cylindrical
5. Magnetic Quantum number is related to
A) size
B) shape
C) orientation
D) spin
6. Number of electrons that can be accommodated in f sub-shell is
A) 2
B) 8
C) 32
D) 14
7. An electron spinning in clock-wise direction is represented as
A) →
B) ←
C) ↓
D) ↑
8. The scientist who invented elliptical orbits is
A) Bohr
B) Rutherford
C) Sommerfeld
D) Zeeman
9. Among 3p, 4s, 3d and 4p. The orbital having least energy is
A) 4s
B) 3p
C) 3d
D) 4p
10.
11. The phenomenon of black body radiation was successfully explained by
A) Rutherford
B) Thomson
C) Max Planck
D) Schrodinger
12. The electronic configuration of copper is
A) [Ar] 4s1 3d10
B) [Ar] 4s2 3d10
C) [Ar] 4s1 3d5
D) [Ar] 4s2 3d8
13. Orbital without any directional character is
A) s
B) p
C) d
D) f
14. Splitting of spectral lines in presence of magnetic field is called
A) Stark Effect
B) Zeeman Effect
C) Bohr's Model
D) Nucleons
15. Orbitals will have
A) Crests
B) Troughs
C) Anti-nodal regions
D) Nodal regions
II. Fill in the Blanks:
(1/2 Mark Each)
16. Quantum theory of radiation is proposed by _______
17. Rutherford proposed planetary model based on his _______ experiment.
18. E2 – E1 = hí where í is _______
19. The electronic configuration of zinc is _______
20. In stationary orbits, the energy of the electron is _______
21. 3d10 4s1 is the electronic configuration of _______
22. The 's' orbital of L-shell is called _______
23. After filling the 3d orbital, the electron enters into _______ orbital.
24. The sub-states are also called _______
25. _______ proposed spin Quantum number.
26. The element with high electron affinity is _______
27. The _______ orbitals correspond to l = 2.
28. 1s2 2s2 2p6 3s1 is the electronic configuration of the element _______
29. Two electrons in an orbital will have _______ spins.
30. The value of Planck's constant is _______ erg.sec.
31. The electrons revolve round the nucleus and _______ on their own areas.
32. As the n value increases, the size and energy of the orbit also _______
33. Quantum means _______ of energy.
34. (n + l) value of 4s is _______ that of 3p.
35. The electronic configuration of Argon is _______
III. Match the Following:
(1/2 Mark Each)
I. Group - A Group - B (no. of electrons)
36. K-shell [ ] A) 8
37. L-shell [ ] B) 18
38. M-shell [ ] C) 32
39. N-shell [ ] D) 2
40. P-orbitals [ ] E) 6
II. Group - A Group - B
41. Nitrogen [ ] A) [Ne] 3s1
42. Sodium [ ] B) [He] 2s2 2p3
43. Copper [ ] C) [Ar] 4s2 3d10
44. Zinc [ ] D) [Ar] 4s1 3d5
45. Chromium [ ] E) [Ar] 4s1 3d10
III. Group - A Group - B
46. Stationary orbits [ ] A) Schrodinger
47. Elliptical orbits [ ] B) Louis De Broglie
48. Dual nature of electron[ ] C) Max Planck
49. Wave equation [ ] D) Neils Bohr
50. Quantum theory [ ] E) Sommerfeld
(ANSWERS)
1. C
2. D
3. C
4. B
5. C
6. D
7. D
8. C
9. B
10. A
11. C
12. A
13. A
14. B
15. D
II.
16. Max Planck
17. á-ray scattering
18. frequency of radiation
19. [Ar] 4s23d10
20. constant
21. copper
22. 2s
23. 4p
24. sub-shells
25. Uhlenbeck and Goldsmith
26. chlorine
27. d-orbitals
28. sodium
29. opposite
30. 6.625×10–27erg.sec
31. spin
32. increases
33. a packet
34. equal
35. [Ne]3s23p6
III.I.
36. D
37. A
38. B
39. C
40. E
II.
41. B
42. A
43. E
44. C
45. D
III.
46. D
47. E
48. B
49. A
50. C
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