Atomic Structure Test

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Atomic Structure Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

Isotopes of an element differ in their number of

A
electrons

B
protons

C
neutrons

D
all the above

Solution

Isotopes are variants of a particular chemical element which differ in neutron number, although all isotopes of a given element have the same number of protons in each atom.
Question 2
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Deuterium is a/an _____ of hydrogen.

A
isotope

B
isomer

C
compound

D
None of these

Solution

Deuterium is an isotope of hydrogen.
Question 3
1 / -0

When alpha particles are passed through a thin metal foil, only one out of thousands of particles is rebounded. This observation leads to the conclusion that

A
positively charged particles are concentrated at the centre of the atom and occupy very less space

B
a large number of electrons are revolving around the nucleus of the atom

C
a unit positive charge is only present inside an atom

D
a massive sphere with larger negative charge and unit positive charge is present at the centre of the atom

Solution

When alpha particles are sent through a thin metal foil, only one out of ten thousands of them is rebounded. This observation leads to the conclusion that positively charged particles are concentrated at the centre of the atom.
Question 4
1 / -0

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

A
K, L

B
L, M

C
M, N

D
N, O

Solution

N, O has the least energy difference as they are the outermost shells.
Question 5
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Which one of the following shows the group of atoms having the same number of neutrons in their nuclei?

A
Na, Mg, AI

B
U, U, U

C
C, O, N

D
Ca, C, N

Solution

Number of neutrons = 14 - 6 = 16 - 8 = 15 - 7 = 8
Question 6
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The nucleus of hydrogen atom consists of

A
one neutron

B
one proton

C
one electron

D
one proton and one neutron

Solution

In hydrogen nucleus there is only one proton and no neutron.
Question 7
1 / -0

Who discovered neutrons?

A
Thomson

B
Chadwick

C
Bohr

D
Rutherford

Solution

An atom comprises of three types of elementary particles called electrons, protons and neutrons. Neutron was discovered by a British Physicist named James Chadwick.
Question 8
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Atoms of an element differ from atoms of all the other elements in

A
atomic number and electronic configuration

B
atomic number and number of valence electrons

C
number of neutrons and electronic configuration

D
number of neutrons and number of valence electrons

Solution

Atoms of an element differ from atoms of all the other elements in atomic number and electronic configuration only. The number of neutrons and valence electrons can be the same for two or more elements.
Question 9
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For which of the following, only integers are possible?

I. Valency
II. Oxidation state
III. Atomic number
IV. Atomic weight

A
Both I, II and III

B
Both I, III and IV

C
Both I and III

D
Both III and IV

Solution

Valency, oxidation state and atomic number are always written as integers. But, atomic weight can be in decimals.
Question 10
1 / -0

What is the atomic number of an element that possesses 20 electrons in its N - orbital?

A
50

B
38

C
48

D
40

Solution

In N - orbital, there are 20 electrons. That means,
K-shell = 2 electrons
L-shell = 8 electrons
M-shell = 18 electrons
N-shell = 20 electrons
Total = 48 electrons
Question 11
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Atomic weight of various elements is referred by taking standard

A
hydrogen as 1.0000

B
oxygen as 16.0000

C
carbon as 12.0000

D
nitrogen as 14.0000

Solution

Since 1961 the standard unit of atomic weight has been one-twelfth the weight of an atom of the isotope Carbon - 12. The atomic weight of Carbon is 12.0107.
Question 12
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Which one of the following has variable valency?

A
Carbon

B
Sulphur

C
Nitrogen

D
Aluminium

Solution

Sulphur has a variable valency because Sulfur has 6 electrons in its outermost shell and has empty orbitals (3d, 4s). These orbitals can participate in bonding and allow these atoms to their valencies Sulphur can donate all 6 electrons and therefore its valency is 6 e.g. H₂SO₄. Sulphur displays valences of four (in sulphur dioxide, SO₂), and eight (in sulphur hexafluoride, SF₈).
Question 13
1 / -0

The valency of cupric ion is

A
2

B
3

C
1

D
4

Solution

When Copper has 2 valence electrons it is called as cupric. Hence valency of cupric is +2.
Question 14
1 / -0

What is the valency of an element having atomic number 54?

A
2

B
1

C
0

D
3

Solution

Xenon has atomic no. = 54, there are no valence electrons. Hence valency is zero.
Question 15
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Which among the following represents isobars?

A
_bX^a, _{b + 1}Y^a

B
_bX^a, _cY^b

C
_bX^a, _b-1Y^a-2

D
_bX^a, _bY^a+1

Solution

Isobars are the elements having same mass number. Option 1 shows isobars having same mass number i.e., \'a\'.
Question 16
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What is the maximum number of electrons present in N - shell?

A
8

B
18

C
64

D
32

Solution

Maximum number of electrons in N-shell is 32. The electronic configuration is 2, 8, 18, 32,........ K, L, M, N,........
Question 17
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Which of the following correctly defines Zeeman effect?

A
Splitting of atomic spectral lines in the presence of an electric field

B
Splitting of atomic spectral lines in the presence of a magnetic field

C
Movement of electrons in the outermost energy orbital

D
Excitation of electrons from one energy level to another

Solution

Splitting of atomic spectral lines in the presence of a magnetic field is called Zeeman effect.
Question 18
1 / -0

How many electrons are there in the valence shell of an element having atomic number 16?

A
8

B
6

C
2

D
4

Solution

Number of valece electrons is 6 because of the electronic configuration 2, 8, 6.
Question 19
1 / -0

Which among the following pairs has different number of valence electrons?

A
Na⁺, Al³⁺

B
P^3-, Ar

C
Li⁺, Ar

D
O^2-, F^–

Solution

Valence electrons of Li⁺ are 2, while that of Ar is 8.
In all other options, valence electrons of the given species are same.
Na⁺, Al³⁺, P^3-, Ar, O^2-, F^– all have a stable octet configuration(eight electrons in the valence shell).
Question 20
1 / -0

Two elements A and B combine forming a compound whose molecular formula is AB₂. The valences of A and B are

A
+ 2 and - 2 respectively

B
+ 1 and - 2 respectively

C
+ 3 and - 2 respectively

D
+ 4 and - 2 respectively

Solution

Valencies of A and B can be +2 and -1 or +4 and -2 or ....... Hence, valencies of A and B according to options is +4 and -2.