Structure of Atom Test

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Structure of Atom Test - 4

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Question 1
4 / -1

Principle Quantum number describes?

A
Size of the orbital.

B
Shape of orbital

C
Spin of orbital.

D
Orientation of an orbital.

Solution

The principal quantum number (n) describes the size of the orbital.
Example: Orbitals for which n = 2 are larger than those for which n = 1.
Question 2
4 / -1

The atoms of different isotopes of the same element differ from each other in the number of:

A
Protons

B
Neutrons

C
Electrons in the inner shell only

D
Electrons in outer most shell only
Solution
Isotopes of an element will contain the same number of protons and electrons but will differ in the number of neutrons they contain.
In other words, isotopes have the same atomic number because they are the same element but have a different atomic mass because they contain a different number of neutrons.
Question 3
4 / -1

The radius of the nucleus of an atom is approximately:

A
10^-15 m

B
1 nm

C
10^-10 m

D
10^-12 m

Solution

It is found that the radius of the nucleus is approximately 10^-¹⁵ m.
Question 4
4 / -1

An element has 18 electrons, and 20. neutrons. Its charge is -2. What is its mass number?

A
32

B
36

C
39

D
40

Solution

The mass of the atom is the collective number of protons and neutrons in the nucleus of the atom. (Electrons have negligible mass in comparison to the mass of the nucleus).
Atomic number= number of protons= number of positive charges = Z
Mass number= number of protons and neutrons= N
Number of electons= number of protons = Z (if an atom is electrically neutral)
Number of electons = Z - charge on the atom (in case of ions)
Number of electrons (=18) = Z-(charge on ion=-2)
Z = 18–2 = 16
Number of protons = Z = 16
Number of neutrons = 20
N = Z + number of neutrons
N = 16+20 = 36
Thus, mass number of the atom is 36.
Question 5
4 / -1

Which of the following statements is not correct about the characteristics of cathode rays?

A
They start from the cathode and move towards the anode.

B
They travel in a straight line in the absence of an external electrical or magnetic field.

C
Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray tube.

D
Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.
Solution
The cathode rays start from the cathode and move towards the anode.
These rays themselves are not visible but their behaviour can be observed with the help of phosphor materials such as ZnS.
In the absence of an electrical or magnetic field, these rays travel in straight lines.
In the presence of an electrical or magnetic field, the behaviour of cathode rays is similar to that expected from negatively charged particles, suggesting that the cathode rays consist of negatively charged particles, called electrons.
The characteristics of cathode rays (electrons) do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube.
Hence the correct answer is option B.
Question 6
4 / -1

Which model describes that there is no change in the energy of electrons as long as they keep revolving in the same energy level and atoms remains stable?

A
Rutherford Model

B
Bohr’s Model

C
J.J Thomson Model

D
None of the above
Solution
Bohr Model of atom:

An atom is made up of three particles: Electrons, neutrons and protons.

The protons and neutrons are located in a small nucleus at the centre of the atom.

The electrons revolve rapidly around the nucleus at the centre of the atom.

There is a limit to the number of electrons that each energy level can hold.

Each energy level is associated with a fixed amount of energy.

There is no change in the energy of electrons as long as they keep revolving in the same energy level.

Bohr explained the stability through the concept of revolution of electrons in different energy levels.

The change in the energy of an electron occurs when it jumps from lower to higher energy levels. When it gains energy, it excites from lower to higher and vice versa.
Thus energy is not lost and the atom remains stable.
Question 7
4 / -1

The number of radial nodes for 3p orbital is:

A
3

B
4

C
2

D
1
Solution
Number of radial nodes = n - 1 – 1
For 3p orbital, n = 3 – 1 – 1 = 1
Number of radial nodes = 3 – 1 – 1 = 1.
Question 8
4 / -1

Atomic mass of an element is equal to the sum of?

A
Electron and neutron

B
Electron and proton

C
Proton and neutron

D
None of the above
Solution
Atomic mass includes the mass of subatomic particles that is protons, neutrons and electrons.
Generally, atomic mass can be expressed in grams.
Atomic mass is the sum of the mass of protons, the mass of electrons and mass of neutrons.
Since the mass of the electron is 1/2000 times lesser than the mass of proton and neutron. Therefore, the electrons do not contribute to the mass of the atom.
Hence the correct answer is C.
Question 9
4 / -1

Thomson’s plum pudding model explained:

A
Existence of electrons.

B
Electrical neutrality of an atom.

C
Existence of atoms.

D
Electrons move in fixed circular orbits.
Solution
An atom consists of a positively charged sphere with electrons filled into it. The negative and positive charges present inside an atom are equal and as a whole, an atom is electrically neutral.
Thomson’s model of the atom as compared to plum pudding and watermelon.
He compared the red edible part of the watermelon to a positively charged sphere whereas the seeds of watermelon to negatively charged particles.
Question 10
4 / -1

Which of the following conclusions could not be derived from Rutherford’s α -particle scattering experiment?

A
Most of the space in the atom is empty.

B
The radius of the atom is about 10^–10 m while that of nucleus is 10^–15 m.

C
Electrons move in a circular path of fixed energy called orbits.

D
Electrons and the nucleus are held together by electrostatic forces of attraction.
Solution
Concept of electrons moving in a circular path of fixed energy called orbits was put forward by Bohr and not derived from Rutherford's scattering experiment.
Out of a large number of circular orbits theoretically possible around the nucleus.
The electron revolves only in those orbits which have a tired value of energy Hence, these orbits are called energy level or stationary states.
Question 11
4 / -1

The charge on electron was determined by:

A
Crooks

B
Bohr

C
Milliken

D
Schrodinger

Solution

The charge on electrons was determined by Milliken by using an oil drop experiment.
Question 12
4 / -1

The nature of positive rays depends on?

A
The nature of discharge tube.

B
The nature of residual gas.

C
The nature of electrode.

D
All of above
Solution
The nature of positive rays produced in a vacuum discharge tube depends upon the nature of the gas-filled.
The positive rays consist of positive ions obtained by removing one or more electrons from gas molecules.
Question 13
4 / -1

The nucleus of a tritium atom, ³H, contains

A
three protons

B
three neutrons

C
two protons and one neutron

D
two neutrons and one proton
Solution
Tritium (³H) is the only radioactive isotope of hydrogen.
The nucleus of a tritium atom consists of a proton and two neutrons.
Question 14
4 / -1

Which of the following is true about electron?

A
It is negatively charged and is lighter than a proton.

B
It is negatively charged and has same mass as a proton.

C
It is positively charged and has no mass.

D
None of the above
Solution
Electrons are negatively charged particles.
The mass of the electron is 1/2000 times lesser than the mass of proton and neutron. Therefore, the electrons do not contribute to the mass of the atom.
An electron has an electric charge of -1.602 × 10^-19 coulombs) which is equal and opposite to the charge of a proton.
Electrons are subatomic particles found outside the nucleus, unlike protons and neutrons, which are present inside the nucleus.
Therefore, the correct answer is A.
Question 15
4 / -1

Neutron is a fundamental particle which carries?

A
No charge and mass of one unit.

B
A charge of +1 and mass of l unit.

C
No charge and no mass.

D
A charge -1 unit and no mass.
Solution
Proton and electrons are electrically charged, neutrons have no charge they are electrically neutral.
The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass unit (AMU).
(An atomic mass unit equals about 1.67×10−27 kilograms.)
Hence the correct answer is A.

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Structure of Atom Test - 4

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Structure of Atom Test - 4

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Question 1

Size of the orbital.

Shape of orbital

Spin of orbital.

Orientation of an orbital.

Solution

Question 2

Protons

Neutrons

Electrons in the inner shell only

Electrons in outer most shell only

Solution

Question 3

10-15 m

1 nm

10-10 m

10-12 m

Solution

Question 4

32

36

39

40

Solution

Question 5

They start from the cathode and move towards the anode.

They travel in a straight line in the absence of an external electrical or magnetic field.

Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray tube.

Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.

Solution

Question 6

Rutherford Model

Bohr’s Model

J.J Thomson Model

None of the above

Solution

Question 7

3

4

2

1

Solution

Question 8

Electron and neutron

Electron and proton

Proton and neutron

None of the above

Solution

Question 9

Existence of electrons.

Electrical neutrality of an atom.

Existence of atoms.

Electrons move in fixed circular orbits.

Solution

Question 10

Most of the space in the atom is empty.

The radius of the atom is about 10–10 m while that of nucleus is 10–15 m.

Electrons move in a circular path of fixed energy called orbits.

Electrons and the nucleus are held together by electrostatic forces of attraction.

Solution

Question 11

Crooks

Bohr

Milliken

Schrodinger

Solution

Question 12

The nature of discharge tube.

The nature of residual gas.

The nature of electrode.

All of above

Solution

10^-15 m

10^-10 m

10^-12 m

The radius of the atom is about 10^–10 m while that of nucleus is 10^–15 m.