Structure of Atom Test

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Structure of Atom Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

The atom of which of the given elements does not have any neutron in the nucleus?

A
Helium

B
Neon

C
Hydrogen

D
Oxygen

Solution

The atomic number as well as the mass number of Hydrogen is one.
There is only one proton in the nucleus which accounts for the mass of the hydrogen atom.
It does not have any neutron.
Question 2
1 / -0

The nuclide symbol of an element 'X' is .The number of neutrons in the nucleus is:

A
6

B
4

C
7

D
8

Solution

The element is Carbon.
Number of protons = Number of electrons = 6
Number of neutrons = 14 - 6 = 8
Question 3
1 / -0

Which among the following is the smallest in size?

A
N³⁻

B
O²⁻

C
F⁻

D
Na⁺

Solution

All the given ions are isoelectronic with the same number of electrons (10 electrons) and also have the same electronic configuration. Na⁺ has the smallest ionic radius because of greater nuclear charge (10 electrons are pulled by 11 protons).
Question 4
1 / -0

Identify the incorrect statement about an atom.

A
Electrons are negatively charged particles.

B
The mass of the neutron is equal to that of a proton.

C
The net charge of the nucleus is zero as the charge of a neutron is equal in magnitude but opposite in nature to that of a proton.

D
The number of electrons and protons in an atom is equal.

Solution

The nucleus contains protons, which are positively charged and neutrons, which are neutral particles.
Hence, the net charge of the nucleus is positive.
Question 5
1 / -0

Which observation of Rutherford's alpha-scattering experiment pointed to the the fact that the radius of the atomic nucleus is very small in comparison to that of the atom?

A
Most of the alpha particles passed through the atom.

B
Some of the alpha particles were deflected through small angles.

C
Some of the alpha particles were deflected through large angles.

D
One in 12,000 alpha-particles retraced its path.

Solution

Since very few alpha particles retraced their path, it implied that the nucleus in which all the positive charge and almost the entire mass of the atom is concentrated occupies a very small space within the atom. Only those alpha particles which travelled very close to the nucleus retraced their path.
Question 6
1 / -0

Which of the following statements about the K-atom and K⁺ ion is incorrect?

A
K-atom being neutral is more stable.

B
K⁺ has a higher effective nuclear charge.

C
K⁺ has a smaller radius.

D
K-atom is monovalent.

Solution

K (Z = 19); electronic configuration: 2, 8, 8, 1
K⁺ has electronic configuration: 2, 8, 8 which is also the configuration of argon.
K⁺ is more stable due to its stable octet configuration.
Hence, statement (1) is incorrect.
Question 7
1 / -0

Which of the following will have the same chemical properties?

A
Isobars

B
Isotopes

C
Both isotopes and isobars

D
None of the above

Solution

Isotopes are atoms of the same element, having the same number of protons and electrons.
The electronic configuration as well as the valency is the same for isotopes and hence they have same chemical properties.
Question 8
1 / -0

Select from among the following the pair in which the atoms are not isobars.

A

B

C

D

Solution

This is a pair of isotopes of carbon.
Question 9
1 / -0

Canal Ray experiment led to the discovery of

A
protons

B
neutrons

C
electrons

D
nucleus

Solution

Canal rays or anode rays, discovered by E. Goldstein, consist of positively charged particles. They led to the discovery of sub-atomic particles called protons.
Question 10
1 / -0

Which of the following statements is not a postulate of Bohr's model for a hydrogen atom?

A
Energy of the orbits around the nucleus is quantized.

B
The electron in the orbit nearest to the nucleus has the lowest energy.

C
Electrons revolve in different orbits around the nucleus.

D
The position and velocity of electrons in the orbits cannot be determined simultaneously.

Solution

The uncertainty principle was given by Heisenberg, which pointed out that the position and velocity of the electrons in the orbits cannot be determined simultaneously.
Question 11
1 / -0

Which among the following pairs of shells has the least energy difference between two adjacent orbits?

A
K and L

B
L and M

C
M and N

D
N and O

Solution

On moving outward from the nucleus, the energy of the shells increases, but the difference between the energy levels decreases. Therefore, among the given options, the difference between the energies will be the least for N (n = 4) and O (n = 5).
Question 12
1 / -0

An atom has 2K, 8L and 5M electrons. Choose the correct statement(s) regarding it from the following:

A. Trivalent anion of this atom will have 12 protons in its nucleus.
B. Trivalent cation of this atom will have 6 p-electrons in it.
C. This atom forms an amphoteric oxide of formula X₂O₃.
D. One of its allotropes is tetraatomic (X₄).

A
A and B only

B
B only

C
B and C only

D
B and D only

Solution

The element is phosphorus (P), which exists as P₄molecule, and its trivalent cation (P⁺³) will have 6 p-electrons in it.
₁₅P = 1s² 2s² 2p⁶ 3s² 3p³
₁₅P³⁺ = 1s² 2s² 2p⁶ 3s²
Phosphorous does form trivalent anions, but the number of protons in the nucleus is 15 (atomic number) because the protons are not lost or transferred during chemical bonding. Hence, statement 'A' is incorrect.
The oxide of phosphorous P₂O₃ is acidic. Hence, statement 'C' is incorrect.
Thus the statements B and D are correct and option (4) is correct.
Question 13
1 / -0

If the N-shell is the outermost shell of the atom of an element, then what is the maximum number of electrons that it can accommodate?

A
8

B
18

C
64

D
32

Solution

Although the N-shell can accommodate 32 (2 4²) electrons, but if it is the outermost shell, it cannot have more than 8 electrons.

Question 14

1 / -0

Which pair of elements has the same number of electrons in their L-shell?

N and O

Al and S

Li and Na

Be and B

Solution

Element	Electronic Configuration
	K	L	M
N (Z = 7)	2	5
O (Z = 8)	2	6
Al (Z = 13)	2	8	3
S (Z = 16)	2	8	6
Li (Z = 3)	2	1
Na (Z = 11)	2	8	1
Be (Z = 4)	2	2
B (Z = 5)	2	3

Question 15
1 / -0

Which of the following statements DO NOT match with the postulates of Bohr's model of atom?

(a) Electrons are revolving around the nucleus in specified paths called orbits/shells.
(b) Each shell is associated with definite amount of energy.
(c) Electron, while revolving through a particular shell, can increase or decrease its energy.
(d) Energy of the shells decreases as their distance from the nucleus increases.

A
(c) and (d)

B
(b) and (c)

C
(a) and (c)

D
(b) and (d)

Solution

The energy of an electron in a particular shell is quantized.
Energy of shells increases with an increase in the distance from the nucleus.
Question 16
1 / -0

When an electron in the M-shell of an atom gains energy, it moves to

A
K-shell

B
L-shell

C
M-shell

D
N-shell

Solution

On gaining energy, an electron is transported to a higher energy level.
Question 17
1 / -0

Which one of the following symbols represents a species containing 11 protons, 12 neutrons and 10 electrons?

A
²³Na⁺

B
²¹Ne

C
²³Na

D
²³Ne⁺

Solution

p = 11
e = 10
n = atomic mass - atomic number = 23 - 11 = 12
Question 18
1 / -0

Structures of nuclei of three atoms X, Y and Z are as follows:

(A) X has 90 protons and 146 neutrons.
(B) Y has 92 protons and 146 neutrons.
(C) Z has 90 protons and 148 neutrons.

Which of the following statements is correct based on the above data?

A
X and Z are isotopes; Y and Z are isobars.

B
X and Y are isotopes; X and Z are isobars.

C
Y and Z are isobars; X and Y are isotopes.

D
X and Z are isotopes; X and Y are isobars.

Solution

X and Z both have atomic number 90 and mass numbers 236 and 238, respectively.
Hence, they are isotopes.
Y and Z have atomic numbers 92 and 90, respectively, and the same mass number, 238.
Hence, they are isobars.
Question 19
1 / -0

Which among the following shows the group of atoms having the same number of neutrons in their nuclei? [Given, the atomic masses of the elements Na, Mg, Al, Be, Ca, C, O and N are 23 u, 24 u, 27 u, 9 u, 40 u, 14 u, 16 u and 15 u, respectively]

A
Na, Mg, Al

B
Be, Mg, Ca

C
C, O, N

D
Ca, C, N

Solution

Carbon has 8 (14 - 6) neutrons.
Oxygen has 8 (16 - 8) neutrons.
Nitrogen has 8 (15 - 7) neutrons.
Hence, ₁₄C⁶, ₁₆O⁸ and ₁₅N⁷ are isotones.
Question 20
1 / -0

An element has two isotopes with mass numbers 16 and 18 and their average atomic weight is 16.5. What will be the percentage compositions of these isotopes?

A
75%, 25%

B
35%, 65%

C
50%, 50%

D
33.33%, 66.67%

Solution

Let there be x% of and (100 - x)% of .

Average mass = + = 16.5

Therefore, is 75% and is 25%.

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Structure of Atom Test - 3

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Structure of Atom Test - 3

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Question 1

Helium

Neon

Hydrogen

Oxygen

Solution

Question 2

6

4

7

8

Solution

Question 3

N3−

O2−

F−

Na+

Solution

Question 4

Electrons are negatively charged particles.

The mass of the neutron is equal to that of a proton.

The net charge of the nucleus is zero as the charge of a neutron is equal in magnitude but opposite in nature to that of a proton.

The number of electrons and protons in an atom is equal.

Solution

Question 5

Most of the alpha particles passed through the atom.

Some of the alpha particles were deflected through small angles.

Some of the alpha particles were deflected through large angles.

One in 12,000 alpha-particles retraced its path.

Solution

Question 6

K-atom being neutral is more stable.

K+ has a higher effective nuclear charge.

K+ has a smaller radius.

K-atom is monovalent.

Solution

Question 7

Isobars

Isotopes

Both isotopes and isobars

None of the above

Solution

Question 8

Solution

Question 9

protons

neutrons

electrons

nucleus

Solution

Question 10

Energy of the orbits around the nucleus is quantized.

The electron in the orbit nearest to the nucleus has the lowest energy.

Electrons revolve in different orbits around the nucleus.

The position and velocity of electrons in the orbits cannot be determined simultaneously.

Solution

Question 11

K and L

L and M

M and N

N and O

Solution

Question 12

A and B only

B only

B and C only

B and D only

Solution

Question 13

8

18

64

N³⁻

O²⁻

F⁻

Na⁺

K⁺ has a higher effective nuclear charge.

K⁺ has a smaller radius.

²³Na⁺

²¹Ne

²³Na

²³Ne⁺