Tag: chemistry

Questions Related to chemistry

Nuclides having the same atomic and mass numbers are known as :

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. isotones

  2. isomers

  3. isobars

  4. isotopes

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Correct Option: B
Explanation:

Nuclides having the same atomic and mass numbers are known as Isomers.

An atom that has an unbalanced ratio of neutrons to protons in the nucleus seeks to become more stable. The unbalanced or unstable atom tries to become more stable by changing the number of neutrons and/or protons in the nucleus. This can happen in several ways:

  • converting neutrons to protons
  • converting protons to neutrons
  • ejecting an alpha particle (two neutrons and two protons) from the nucleus.

 Isotones :any of two or more species of atoms or nuclei that have the same number of neutrons.

Isobars are atoms of different chemical elements that have the same number of nucleons.

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number.

The nucleus of the hydrogen atom is called as:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. neutron

  2. electron

  3. proton

  4. nucleons

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Correct Option: C
Explanation:

The nucleus of Hydrogen atom is called as proton as it has only $1$ proton in it . Thus correct answer is option C.

Nucleus is composed of two kinds of subatomic particles: 

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. protons and neutrons

  2. electrons and neutrons

  3. protons and electrons

  4. none of the above

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Correct Option: A
Explanation:

Nucleus is composed of protons and neutrons.

An atom has two main regions. Which are those?

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. Planetary electrons and energy levels

  2. Nucleus and kernel

  3. Principal energy levels and energy sublevels

  4. Nucleus and energy levels

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Correct Option: D
Explanation:

An atom has two main regions, these include nucleus and energy levels.
Nucleus contains protons and neutrons. Electrons revolve in circular energy levels.

The nucleus of the atom consists of:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. protons and neutrons

  2. protons and electrons

  3. neutrons and electrons

  4. protons, neutrons and electrons

Show answer
Correct Option: A
Explanation:

The nucleus of the atom consists of protons and neutrons. Electrons are present in extra nuclear part.
Note: Protons, electrons and neutrons are subatomic particles.

Radius of a nucleus is proportional to:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. $A$

  2. ${A}^{{1}/{3}}$

  3. ${A}^{2}$

  4. ${A}^{{2}/{3}}$

Show answer
Correct Option: B
Explanation:

Radius of a nucleus is proportional to $\displaystyle {A}^{{1}/{3}}$
$\displaystyle r=(1.4 \times 10^{-15}) \times {A}^{{1}/{3}}$
Where r is the radius of the nucleus with mass number A.
Here, the unit of radius is meters.  

The ratio of the volume of the atom and the volume of the nucleus is:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. ${10}^{10}$

  2. ${10}^{12}$

  3. ${10}^{15}$

  4. ${10}^{20}$

Show answer
Correct Option: C
Explanation:

The ratio of the volume of the atom and the volume of the nucleus is $\displaystyle 10^{15}$

The radius of an atomic nucleus is of the order of $\displaystyle {10}^{-13} cm$ or $\displaystyle {10}^{-15} m$ or one Fermi unit.

On the other hand, the radius of an atom is of the order of $\displaystyle {10}^{-8} cm$ or $\displaystyle {10}^{-10} m$ or one angstrom unit.

Note:
The radius of nucleus is much smaller than atomic radius.

The ratio of atomic radius to radius of nucleus is $\displaystyle \dfrac {{10}^{-10} m}{{10}^{-15} m}=10^5$

Volume is proportional to cube of radius.

The ratio of atomic radius to radius of nucleus is $\displaystyle  (10^5)^3 = 10^{15}$

Size of the nucleus is:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. $1A^0$

  2. $10^{-16}m$

  3. $10^{-15}m$

  4. $10^{-14}m$

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Correct Option: C
Explanation:

According to Rutherford the nucleus size is ${ 10 }^{ -15 }m$.

Size of the atom ranges from $0.1$to $0.5nm$ 

Which is characteristic of unstable nucleus?

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. $n/p$ ratio is high

  2. Low binding energy

  3. High packing fraction

  4. None of these

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Correct Option: A,B,C
Explanation:

It is the balance of protons and neutrons in a nucleus which determines whether a nucleus will be stable or unstable. Other factors that influence the stability of nucleus are binding energy and high packing fraction. 

So, the characteristics of unstable nucleus are
  1. $\dfrac{n}{p}$ ratio is high
  2. Low binding energy
  3. High packing fraction

The density of nucleus is of the order of:

chemistry the structure of the atom discovery of charged particles the plum pudding atom discovery of electrons and protons

  1. ${ 10 }^{ 5 }kg{ m }^{ -3 }$

  2. ${ 10 }^{ 10 }kg{ m }^{ -3 }$

  3. ${ 10 }^{ 17 }kg{ m }^{ -3 }$

  4. ${ 10 }^{ 25 }kg{ m }^{ -3 }$

Show answer
Correct Option: C
Explanation:

The density of nucleus is about $2.3\times { 10 }^{ 17 }{ ㎏ }/㎥$. The density is same for all nuclei. Thus density of nucleus is of the order ${ 10 }^{ 17 }{ ㎏ }/㎥$