Free Structure of an Atom 02 Practice Test - 9th Grade 

Question 1

Thomson's atomic model could not explain the result of scattering experiment performed by Rutherford.

A.

True

B.

False

SOLUTION

Solution : A

According to Thomson's atomic model, the positive charge is uniformly distributed in the sphere and electrons are embedded in it just like a plum pudding.This implies that when alpha particles are bombarded on the atoms, they should get deflected uniformly.
However, in the Rutherford alpha particle scattering experiment, it was found that rays were deflected in various angles.

Question 2

Which of the following are properties of anode rays?

A.

Anode rays deflect towards negatively charged plate  

B.

Anode rays travel along a straight path in absence of electric and magnetic field

C.

Anode rays are positively charged radiations due to positive charged sub-atomic particles

D.

All of these

SOLUTION

Solution : D

Following are the properties of anode rays:

1) Anode rays deflect towards negatively charged plate.

2) Anode rays travel along a straight path in absence of electric and magnetic field.

3) Anode rays are positively charged radiations due to positive charged sub-atomic particles.

Question 3

_______ atomic model is also known as the plum pudding model.

A. Thomson's
B. Rutherford's
C. Bohr's
D. Dalton's

SOLUTION

Solution : A

J. J. Thomson proposed the plum pudding model.

According to him, the negatively charged electrons were distributed in a sea of positive charge. This model, shown below, resembled to a plum pudding.

Question 4

The mass of the electrons is negligible when compared to protons. 

A. True
B. False

SOLUTION

Solution : A

Atoms have electrons, protons, and neutrons as the fundamental particles.
Subatomic particleMass (kg)Proton1.67262178 × 1027Neutron 1.6749 × 1027Electron 9.10938291 × 1031

Mass of protonMass of electron1.67262178×10279.10938291×1031 = 1840
Thus, mass of electron is 11840, i.e., 0.0005 times that of proton.

Hence, the mass of an electron is negligible when compared to the mass of proton.

Question 5

Identify the conclusions from the Rutherford's alpha ray scattering experiment.

A.

The centre of the atom is empty space

B.

Most of the volume of the atom is empty

C.

The center of the atom has only negative charge

D.

Atomic mass is concentrated at the centre of the atom

SOLUTION

Solution : B and D

According to Rutherford, the atoms are made of two parts: the nucleus and the extra-nuclear part. His experiments proved that the atom is largely empty and has a heavy positively-charged body at the centre called the nucleus. The central nucleus is positively-charged and the negatively-charged electrons revolve around the nucleus.

Question 6

When alpha particles are sent through a thin metal foil, only one out of ten thousand rebounded. This observation led to the conclusion that:

A.

Unit positive charge is only present in an atom

B.

Positively charged particles are concentrated at the centre of the atom

C.

More number of electrons are revolving around the nucleus of the atom

D.

No positive charge is present.

SOLUTION

Solution : B

When alpha particles are sent through a thin metal foil only one out of ten thousand rebounded. Rutherford concluded that positively charged particles are concentrated at the centre of the atom. At the time of the experiment, the atom was thought to be analogous to plum pudding (as proposed by J.J. Thomson), with the negative charges (the plums) found throughout a positive sphere (the pudding). If the plum pudding model were correct, the positive "pudding", being more spread out than in the current model of a concentrated nucleus, would not be able to exert such large Coulombic forces, and the alpha particles should only be deflected by small angles as they pass through.

Question 7

Name the scientist who first measured the e/m ratio of an electron.

A.

J. J Thomson

B.

James Chadwick   

C.

Dalton

D.

Rutherford

SOLUTION

Solution : A

J.J Thomson was the first scientist who measured charge to mass ratio(e/m) of an electron. When a narrow beam of charged particles are projected at constant speed (v) across a magnetic field in a direction perpendicular to the field, the beam of particles experiences a force, which makes them move in a circular path.

Question 8

The charge on an electron is _______ coulombs.

A.

1.602×1019

B.

+1.602×1019

C.

+1.602×1019 

D.

1.602×1019 

SOLUTION

Solution : D

An electron is a negatively charged subatomic particle.
It has a charge of  1.602×1019 coulombs.

Question 9

Which of the following is the correct electronic configuration of sodium atom?

A. 2, 8, 2
B. 2, 5, 2
C. 2, 8, 1
D. 2, 2, 2

SOLUTION

Solution : C

Atomic number of sodium is 11. Thus, it contains 11 protons.

For a neutral atom, the number of  protons is equal to the number of electrons. Hence, for sodium atom, the number of electrons = 11.
The maximum no. of electrons that can be accommodated in a shell is given by 2×n2, where n represents the no. of shell.
Hence, no. of electrons in 
K shell = (2×12) = 2 electrons
L shell = (2×22) = 8 electrons 

Now only one electron is remaining. Thus, M shell accomodates 1 electron.

Hence, electronic configuration of sodium atom is 2, 8, 1.

Question 10

Which of the following metals was used in alpha ray scattering experiment conducted by Rutherford?

A. Gold
B. Silver
C. Sodium
D. Calcium

SOLUTION

Solution : A

In the alpha-ray experiment, Rutherford preferred gold over other metals because it is the most malleable metal. The gold sheet used by Rutherford was about 1000 atoms thick.