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CBSE Questions for Class 9 Chemistry Structure Of The Atom Quiz 1 - MCQExams.com
CBSE
Class 9 Chemistry
Structure Of The Atom
Quiz 1
Radius of the nucleus is measured in
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nanometer
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fermi
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centimeter
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meter
Explanation
Size of nucleus is measured in Fermi ($$fm$$) it is also known as Femtometer ; where $$1fm = 10^{-15} m$$.
Options $$C$$ is correct.
The presence of nucleus in an atom is determined by Rutherford $$\alpha - ray$$ scattering experiment.
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True
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False
Explanation
The $$\alpha - ray$$ scattering experiment proved the presence of nucleus in centre of an atom.
Heaviest particle is
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Meson
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Neutron
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Proton
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electron
Explanation
Heaviest particle of an atome is neutron. It is due to it's weight difference from others. It is 0.18% heavier than the proton which makes it most heaviest.
Option $$B$$ is correct.
The discovery of neutron becomes very late because
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neturons are present in nucleus.
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neturons are highly unstable particle.
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neutron are chargeless.
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neutron do not move.
Explanation
This is because chargeless particles do not undergo any deflection in an electric or magnetic field.
So, option $$C$$ is correct.
Maximum no. of electrons that can be present in M & N shells respectively are ________.
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$$18, 32$$
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$$8, 18$$
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$$32, 50$$
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$$32, 48$$
Explanation
Maximum number of electrons in a shell $$= 2n^{2}$$
For M shell , $$n= 3$$; no. of electrons $$= 2\times 3^{2} = 18$$
For N shell , $$n= 4$$;no. of electrons
$$= 2\times 4^{2} = 32$$
Which of the following has the same number of protons?
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Isobars
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Isoelectronic
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Isotopes
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Isotones
Explanation
Isotopes are elements having the same atomic number but different mass numbers. e.g : $$_1H^1,\ _1H^2,\ _1H^3$$ are isotopes of hydrogen.
Assertion: Atoms are not electrically neutral.
Reason: Number of protons and electrons are different.
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Assertion and reason both are correct statements and reason is correct explanation for assertion.
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Assertion and reason both are correct statements but reason is not correct explanation for assertion.
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Assertion is correct statement but reason is wrong statement.
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Assertion is wrong statement but reason is correct statement.
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Both assertion and reason statements are wrong.
Explanation
Assertion: Atoms are electrically neutral. They do not have net electrical charge.
Reason: Number of protons and electrons are equal. Hence, total positive charges are balanced with total negative charges.
The components used in Rutherford's experiment:
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$$\beta $$ -particles, which impinged on a metal foil and got absorbed
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$$\gamma $$ -rays, which impinged on a metal foil and ejected electrons
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helium atoms, which impinged on a metal foil and got scattered
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helium nuclei, which impinged on a metal foil and got scattered
Explanation
$$He^{++} [\alpha \:particle]$$
The components used in Rutherford's experiment is $$\alpha$$-particles which is actually a helium nuclei.
Which of the following scientists developed the nuclear model of the atom ?
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John Dalton
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Robert Milikan
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Henry Moseley
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Ernest Rutherford
The nucleus of an atom was discovered by
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Rutherford's gold foil experiment
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J. J. Thomson's experiment
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Chadwick's experiment
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Milikan's oil drop experiment
Nucleon contains:
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only protons
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only neutrons
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both protons and neutrons
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electrons, protons, and neutrons
Explanation
Both protons and neutrons are present in the nucleus of an atom. Nucleon is the collective term for protons and neutrons.
The first model of an atom was given by _____________.
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N. Bohr
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E. Goldstein
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Rutherford
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J.J. Thomson
Explanation
Sir J.J Thomson gave the first model of atom.
He by means of cathode-ray experiment discovered the existence of negatively charged particles in an atom which led to the discovery of electrons.
He gave the plum-pudding model of an atom in which electrons are embedded in atom-like currants.
Positive electrons are distributed all over the atom.
Hence, option (D) is correct.
Stability of an atom was successfully explained by Rutherford's atomic model.
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True
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False
Explanation
As per Rutherford model of an atom, electrons revolving around the nucleus would eventually fall in the nucleus. Therefore, the model could not explain the stability of an atom.
Niel Bohr's atomic model was successful in explaining stability of the atom.
In an atom, sub-atomic particle neutron and proton exists in :
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nucleus
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outside nucleus
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orbits
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sub-orbits
Explanation
From atom structure it can be seen that,
In an atom, sub-atomic particle neutron and proton exists in nucleus.
Which of the following sub atomic particle has the highest mass?
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Neutron
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Positron
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Electron
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Proton
Explanation
Neutron is heaviest among all subatomic particles with a mass of 1.0087 amu while proton has a mass of 1.0073 amu. Positron and electron both have a mass of 0.00055 amu.
Match the atomic numbers 4, 14, 8, 15, and 19 with
a metal of valency 1.
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4
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14
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15
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19
Explanation
Atomic no $$19$$ is potassium with configuration of $$2, 8, 8, 1$$ so it have valency of $$1$$. Also potassium is metal.
Valence electrons are those which are present :
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in the innermost orbit
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in the penultimate orbit
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in outermost orbit
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none of the above
Explanation
Valence electrons are electrons that are present in the outermost shell or orbit.
Rutherford's scattering experiment led to the discovery of
:
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nucleus
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presence of neutrons in the nucleus
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both (A) and (B)
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revolving nature of electrons around the nucleus
Explanation
Since only a few light rays were getting deflected by a large angle in the Rutherford gold foil scattering experiment, he concluded that a highly dense nucleus is present in every atom.
The particle used by Rutherford in $$\alpha$$-ray scattering experiment was :
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neutron
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electron
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helium nuclei
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x-rays
Explanation
Rutherford used $$\alpha$$- particles in his scattering experiment which is a helium nuclei.
The shell closest to the nucleus of an atom is:
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M
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N
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L
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K
Explanation
The shell closest to the nucleus of an atom is K. The next shells are L, M, N, and so on.
Charge on a neutron is __________.
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0
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+1
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-1
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None of the above
Explanation
An electron
has a charge of $$-1$$. A proton
has a charge of $$+1$$. A neutron
has an average zero charge.
The element with atomic number 56 is likely to have the same outer shell configuration as the element with atomic number __________.
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12
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18
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14
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30
Explanation
Electronic configuration of the element X is - 2, 8, 8, 18, 18, 2- It has two electrons in outer shell. The element with atomic number 12 also have 2 electrons in its valence shell -2, 8, 2.
Match the atomic numbers 4, 14, 8, 15, and 19 with
a gas of valency 2.
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4
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8
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14
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15
Explanation
Atomic no $$8$$ is oxygen with configuration of $$2, 6$$ so it have valency of $$2$$ and also oxygen is a gas.
The space between proton and electron in hydrogen atom is
:
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absolutely empty
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full of electromagnetic radiation
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full of air
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full of ether
Explanation
According to Bohr's model of an atom, the space between proton and electron in hydrogen atom is absolutely empty.
The fundamental particle which has no charge and has a mass almost equal to that of the positively charged fundamental particle is ________.
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proton
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neutron
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electron
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$$\beta$$-particle
Explanation
The fundamental particle which has no charge and has a mass almost equal to that of the positively charged fundamental particle is the neutron.
Bohr proposed his atomic model based on
:
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oil drop experiment
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planck's quantum theory
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$$\alpha$$-ray scattering experiment
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experiments on conduction of gases
Explanation
Bohr proposed his atomic model based on planck's quantum theory.
Thomson proposed the model of an atom similar to :
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christmas tree
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christmas pudding
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chocolate
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none of the above
Explanation
Thomson proposed the model of an atom be similar to that of a Christmas pudding.
The electrons in a sphere of positive charge were like currants (dry fruits) in a spherical Christmas pudding.
The ratio of energy to frequency of a radiation emitted by an electron is equal to :
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wave length
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velocity of electron
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bohr's radius
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planck's constant
Explanation
The ratio of energy to frequency of a radiation emitted by an electron is equal to Planck's constant.
Who was the first scientist to propose a model for the structure of an atom?
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J.J. Thomson
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Dalton
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Ernest Rutherford
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E. Goldstein
Explanation
J.J. Thomson was the first one to propose a model for the structure of an atom.
Ernest Rutherford carried out his work on discovery of nucleus with:
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silver foil experiment
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gold foil experiment
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$$\displaystyle \beta -$$ particle experiment
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None of the above
Explanation
Ernest Rutherford carried out his work on the discovery of nucleus of an atom with
gold foil experiment.
Rutherford designed an experiment for this. In this experiment, fast-moving $$\alpha $$-particles were made to fall on a thin gold foil.
Hence, option $$B$$ is correct.
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