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CBSE Questions for Class 9 Chemistry Structure Of The Atom Quiz 2 - MCQExams.com
CBSE
Class 9 Chemistry
Structure Of The Atom
Quiz 2
Who is known as the father of nuclear physics?
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Ernest Rutherford
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Dalton
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J.J. Thomson
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E. Goldstein
Explanation
Ernest Rutherford is known as the father of nuclear physics. He is famous for his work on radioactivity and the gold foil experiment that suggested the existence of a nucleus in an atom.
Rutherford's atomic model couldn't explain
:
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the presence of electrons in the atom
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the presence of positive charge in the atom
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the stability of the atom
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the position of the nucleus
Explanation
Rutherford's atomic model couldn't explain the stability of atom but it explained the position of nucleus, presence of positive charge in atom and position of electrons.
Which of the following was carried out by Rutherford in his experiment?
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Fast moving alpha-particles were made to fall on a thin silver foil.
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Fast moving beta-particles were made to fall on a thin gold foil.
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Fast moving alpha-particles were made to fall on a thin gold foil.
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Fast moving gamma-particles were made to fall on a thin gold foil.
Explanation
Ernest Rutherford performed an experiment to understand the structure of atom. In this experiment, fast-moving alpha particles were made to fall on a thin gold foil (100 nm thickness).
Who suggested the distribution of electrons into different orbits of an atom?
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E. Goldstein
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Ernest Rutherford
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Bohr and Bury
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Dalton
Explanation
The arrangement and distribution of electrons in different orbits were given by Bohr and Bury. The arrangement of electrons in different shells and sub-shells is known as the electronic configuration of a particular element.
The combining capacity of an element is called:
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valency
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valence electron
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Both A and B
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None of the above
Explanation
Valency of an element gives the combining power of an element. It determines the number of atoms with which an atom of the element can combine.
For example, the combining capacity or valency of sodium is 1. So, if sodium has to form compounds, it will generally combine with one other atom.
The positively charged center in an atom is called as:
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nucleus
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neutron
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proton
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electron
Explanation
Positively charged center in an atom is called as nucleus.
Which of the following is not true for $$\displaystyle _7N ^{ 14 }$$ ?
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14 is the mass number
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7 is the atomic number
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N is the symbol for nitrogen
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14 is the atomic number
Explanation
The general notation of an element is: $$_Z X^A$$, where X is the symbol of the element, Z its atomic number and A is the mass number.
So, in
$$_7 X^14$$,
14 is the mass number of nitrogen while 7 is the atomic number.
The mass of an atom resides in:
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nucleus
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protons
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electrons
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All of the above
Explanation
The mass of an atom resides in its nucleus as it contains protons and neutrons. Atomic mass is the sum of mass of protons and neutrons.
While revolving in discrete orbits, the electrons do not radiate energy. These orbits or shells are called ________.
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isotope
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isobars
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nucleus
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energy levels
Explanation
While revolving in discrete orbits, the electrons do not radiate energy. These orbits or shells are called energy levels.
On the basis of Rutherford's model of an atom, which sub-atomic particle is present in the nucleus of an atom?
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Protons
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Electrons
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Neutrons
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All of the above
Explanation
On the basis of Rutherford's model of an atom, protons (positively-charged particles) particle are present in the nucleus of an atom.
Atomic number of carbon atom is:
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1
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3
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6
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8
Explanation
Atomic number of carbon atom is 6. Electronic configuration of carbon is given by 2, 4.
The electrons present in the outermost shell of an atom are known as
:
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protons
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neutrons
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octet
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valence electrons
Explanation
The electrons present in the outermost shell of an atom are known as valence electrons.
If atoms of elements have completely filled the outermost shell then their combining capacity or valency is
:
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one
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two
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zero
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five
Explanation
If atoms of elements have a completely filled outermost shell then their combining capacity or valency is zero.
After completely filled shell it's stable so nonreactive.
The electrons first occupy the shell having ______________.
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the lowest energy level or K-shell and then move to the higher energy level L, M, N
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the lowest energy level or L-shell and then move to the higher energy level K, M, N
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the higher energy level or K-shell and then move to the lowest energy level L, M, N
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the higher energy level or L-shell and then move to the lowest energy level L, M, N
Explanation
The following rules are followed for occupying the number of electrons in different energy levels or shells:
The maximum number of electrons present in a shell is given by the formula $$2n^2$$, where ‘n’ is the energy level index, 1,2,3,…. Hence the maximum number of electrons in different shells are as follows:
First orbit or K-shell will be $$= 2 \times 12 = 2$$,
Second orbit or L-shell will be $$= 2 \times 22 = 8$$,
Third orbit or M-shell will be$$ = 2 \times 32 = 18$$,
Fourth orbit or N-shell will be $$= 2 \times 42 = 32$$, and so on.
The maximum number of electrons that can be accommodated in the outermost orbit is 8.
Electrons are not accommodated in a given shell unless the inner shells are filled. That is, the shells are filled in a step-wise manner.
So from the above explanation, it is clear that the electrons occupy the shell having the lowest energy level or K-shell and then move to the higher energy shells L, M, N.
The distribution of electrons in lithium is _________.
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2 (K), 1 (L)
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2 (M), 1 (N)
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2 (K), 1 (N)
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2 (M), 1 (L)
Explanation
Atomic number of Li is 3. The distribution of electrons in lithium atom is 2 (K), 1 (L). There are 2 electrons in the innermost shell (K) and 1 in the outer shell (L).
......... is defined as the number of protons present in the nucleus of an atom.
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Atomic number
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Mass number
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Both A and B
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None of these
Explanation
Atomic number is defined as the number of protons present in the nucleus of an atom and it is denoted by $$Z$$
.
For hydrogen, $$Z = 1$$, because in a hydrogen atom, only one proton is present in the nucleus. Similarly, for carbon, $$Z = 6$$
Who discovered the positively charged particle called proton?
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Chadwick
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Goldstein
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Rutherford
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None of these
Explanation
Ernest Rutherford postulated that an atom has a positively charged center (nucleus) that contains most of the atom's mass.
He suggested that the nucleus contains positively charged particles (protons).
Which of these have the same chemical properties, but their physical properties may be different?
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Atomic number
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Mass number
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Isotopes
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Isobars
Explanation
Isotopes have same chemical properties, but their physical properties might be different.
Chemical properties of an element depend on its atomic number or number of protons. Isotopes of an element have the same atomic number, hence their chemical properties are the same. But their physical properties may vary.
The charge on a neutron is:
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$$-1.602\times10^{-19}C$$
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$$1.602\times10^{-19}C$$
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$$0$$
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None of the above
What tool was Thomson using when he discovered the electron?
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Magnifying Glass
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Hammer
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Cathode Ray
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Microscope
Neutron's relative charge is:
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$$-1$$
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$$+1$$
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$$0$$
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$$-2$$
Explanation
Neutron is a neutral particle that means it has no charge. It was discovered by J.Chadwick in 1932.
Thomson's atomic model concluded that _____ is the constituent particle of all kinds of atoms.
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electron
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protron
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neutron
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none of these
Explanation
Thomson experiments with cathode-ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons.
So, option A is correct.
The distribution of electron in $$Kr$$ is _________.
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$$2(K),\;8(L),\;18(M),\;8(N)$$
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$$2(K),\;1(L),\;18(M),\;8(N)$$
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$$2(K),\;1(L),\;18(M),\;8(N)$$
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$$2(M),\;1(L)$$
Explanation
The atomic number of Kr is $$36$$ and the distribution of electrons in Kr is $$2(K),\;8(L), 18(M), 8(N)$$
Option $$A$$ is correct.
Canal rays are:
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anode rays
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positive rays
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both A and B
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electron rays
Explanation
Canal rays are also known as anode rays. They are positively charged radiations (simply called positive rays) that are in fact a beam of positive ions created by certain types of gas-discharge tubes.
On the basis of the atomic model Rutherford concluded that:
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atoms consist of predominantly empty spaces
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atoms consist of central nucleus containing positively charged particles
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whole of the atomic mass is concentrated in the nucleus
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All are correct
Explanation
On the basis of the atomic model Rutherford concluded that :
(A) atoms consist of predominantly empty spaces
(B) atoms consist of central, tiny nucleus containing positively charged particles.
(C) Whole of the atomic mass is concentrated in the nucleus
Also, positive charge is concentrated in the nucleus. He also concluded that the number of positively charged particles in an atom is exactly equal to the number of extra-nuclear electrons. So an atom is electrically neutral.
Maximum number of electrons that can be accomodated in a shell (in general) is given by the formula
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$$2n$$
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$$2n^2$$
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$$4n$$
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$$n^2$$
Explanation
The maximum number of electrons that can be accommodated in a shell is given by the formula $$2n^2$$, where 'n' is the orbit number or energy level.
The valency of carbon with respect to sodium is :
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$$1$$
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$$2$$
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$$3$$
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$$4$$
Explanation
The valency of carbon is $$4$$ and the valency of sodium is $$1$$ therefore the valency of carbon with respect to (ratio) sodium is $$4$$.
Neutron has no charge but mass equal to that of ________.
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proton
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electron
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Both A and B
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None of the above
Explanation
Neutron has no charge but the mass is equal to that of the proton. It weighs 1 amu.
Find out the correct statement based on Rutherford's atomic model.
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Most of the mass of an atom is concentrated at the center
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Nucleus is very small in size
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Electrons circulate around the nucleus
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All of the above
Explanation
Based on the gold foil experiment, Rutherford found that most of the mass of an atom resides at the positively charged centre called the nucleus. He also suggested that the electrons revolve around the nucleus in circular orbits. Apart from this, he had put forward that the size of the nucleus is very small when compared to the size of the atom. Thus, all the statements are correct. Hence, option D is correct.
The structure of the sodium atom is shown in the figure given alongside. Identify the correct statement.
Sodium has atomic no. .........................
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11
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12
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23
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10
Explanation
Atomic number (z) is the number of protons in an atom. It is also equal to the number of electrons in the atom.
Atomic number = number of protons
So, in this case, the atomic number is $$11$$ which is equal to no. of protons in the nucleus.
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