Tag: structure of atoms

Questions Related to structure of atoms

Statement 1: Neutrons and protons are classified as nucleons.
Statement 2: Neutrons and protons are both located in the principal energy levels of the atom.

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  2. Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  3. Statement 1 is correct but Statement 2 is not correct.

  4. Statement 1 is not correct but Statement 2 is correct.

  5. Both the Statement 1 and Statement 2 are not correct.

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Correct Option: C
Explanation:
A nucleon is a collective name for two important subatomic particles: neutrons and protons. A nucleon is one of either of the two types of subatomic particles (neutrons and protons) which are located in the nucleus of atoms.
electrons are located in the principal energy levels of the atoms so statement 2 is not correct because neutron and proton stay in the nucleus of an atom.

The ratio of neutrons in ${O}^{16}$ and ${O}^{18}$ is

chemistry what is inside atom neutrons discovery of neutrons structure of atoms

  1. $8 : 10$

  2. $4 : 5$

  3. $9 : 8$

  4. $1 : 1$

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Correct Option: A,B
Explanation:

 The ratio of neutrons in $\displaystyle {O}^{16}$ and $\displaystyle {O}^{18}$ is $\displaystyle 4 : 5 \text { or } 8 : 10$
Number of neutrons in $\displaystyle {O}^{16} = 16-8=8$
Number of neutrons in $\displaystyle {O}^{18}=18-8=10$

Which of the following atoms contains the least number of neutrons?  

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. $ _{92}^{235}{U}$

  2. $ _{92}^{238}{U}$

  3. $ _{93}^{239}{Np}$

  4. $ _{93}^{240}{Np}$

Show answer
Correct Option: A
Explanation:

 The number of neutrons is the difference between the mass number and atomic number.
   
$\displaystyle _{92}^{235}{U}$ contains the least number of neutrons

The number of neutrons in $\displaystyle _{92}^{235}{U}$ $\displaystyle = 235-92=143$

The number of neutrons in $\displaystyle _{92}^{238}{U} $ $\displaystyle =238-92=146$

The number of neutrons in $\displaystyle _{93}^{239}{Np}$ $\displaystyle = 239-93=146$

The number of neutrons in  $\displaystyle _{93}^{240}{Np}$ $\displaystyle =240-93=147$

The discovery of neutron came very late because:

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. it is present in nucleus

  2. it is a fundamental particle

  3. it does not move

  4. it does not carry any charge

Show answer
Correct Option: D
Explanation:

The discovery of neutron came very late because it does not carry any charge.

Neutron was discovered by Chadwick.


To overcome the failure of proton-electron hypothesis, Rutherford, in 1920, proposed the existence of neutral particle made from a close combination of proton and electron. He named it a neutron.

In 1932, Lord Chadwick proved the existence of neutron by bombarding lighter elements (boron and beryllium) with alpha particles which resulted in the emission of highly penetrating neutral radiation.

Hence, the correct option is $\text{D}$.

The mass of neutron is of the order of: 

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. ${10}^{-27} kg$

  2. ${10}^{-26} kg$

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

  4. ${10}^{-24} kg$

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Correct Option: A
Explanation:

The mass of neutron is of the order of $\displaystyle {10}^{-27} kg$

It is equal to $\displaystyle 1.674 \times {10}^{-27} kg$ or $\displaystyle 1.674 \times {10}^{-24} g$. It is also equal to 1.0087 amu.

Neutrino has

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. charge $+1$, mass $1$

  2. charge $0$, mass $0$

  3. charge $-1$, mass $1$

  4. charge $0$, mass $1$

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Correct Option: B
Explanation:

Neutrino has charge 0, mass 0. It was postulated by Fermi in 1934.

The mass of $ _{3}^{7}{Li}$ is $0.042$ less than the mass of $3$ protons and $4$ neutrons. The binding energy per nucleon in $ _{3}^{7}{Li}$ is:

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. $5.6 MeV$

  2. $56 MeV$

  3. $0.56 MeV$

  4. $560 MeV$

Show answer
Correct Option: A
Explanation:

The mass defect for $\displaystyle _3^7Li$  is $\displaystyle \Delta m = 0.042$  amu.
1 amu $\displaystyle =931.5$ MeV
Binding energy $\displaystyle = 0.042 \times 931.5 = 39.123$ MeV
Total number of nucleons in $\displaystyle _3^7Li$  is 7 (3 protons and 4 neutrons).
Binding energy per nucleon $\displaystyle =  \dfrac {39.123}{7} = 5.6$ MeV.

The introduction of a neutron into the nuclear composition of an atom would lead to a change in:

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. its atomic mass

  2. its atomic number

  3. the chemical nature of the atom

  4. number of the electron also

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Correct Option: A
Explanation:

The introduction of a neutron into the nuclear composition of an atom would lead to a change in its atomic mass.
However, its atomic number, the chemical nature of the atom and the number of the electron s will remain unchanged as they are related to the number of protons and are independent of the number of neutrons.

Note: The atomic mass is equal to the sum of the number of protons and the number of neutrons. Chemical properties depends on number of electrons which are equal to number of protons in neutral atom. They are also equal to atomic number.

What is the order of density of neutron?

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. $10^3$ kg/cc

  2. $10^6$ kg/cc

  3. $10^{12}$ kg/cc

  4. $10^2$ kg/cc

Show answer
Correct Option: C
Explanation:

$Radius\ of\ neutron = 1\times 10^{-13}$
$\therefore$ volume $=\dfrac{4}{3}\times \pi  r^{3} = \frac{4}{3}\times \pi (1\times 10^{-13})^{3} = \dfrac{4}{3}\times \pi \times 10^{-39}$
Mass of neutron $=1.6\times 10^{-27}$
$\therefore$ Density $=\dfrac{mass}{volume}$ $=\dfrac{3\times 1.6\times 10^{-27}}{4\times \pi \times 10^{-39}} = \dfrac{4.8}{4\times \pi }\times 10^{12}$ kg/cc

If A = Atomic mass, Z = Atomic number, then number of neutrons is equal to ?

chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. $A - Z$

  2. $A + Z$

  3. $Z - A$

  4. $\frac{Z}{A}$

Show answer
Correct Option: A
Explanation:

If A = Atomic mass, Z = Atomic number then the number of neutrons is equal to: 


$ A$ = Atomic mass = Number of protons + Number of neutrons

$Z$ = Atomic Number = Number of protons$

$A$ = $Z$ + Number of neutrons

Number of neutrons = $Z-A$