Tag: structure of atoms

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Multiple choice chemistry structure of the atom neutrons discovery of neutrons 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.

  1. <p>Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.</p>

  2. <p>Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.</p>

  3. <p>Statement 1 is correct but Statement 2 is not correct.</p>

  4. <p>Statement 1 is not correct but Statement 2 is correct.</p>

  5. <p>Both the Statement 1 and Statement 2 are not correct. </p>
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice chemistry what is inside atom neutrons discovery of neutrons structure of atoms

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

  1. $8 : 10$
  2. $4 : 5$
  3. $9 : 8$
  4. $1 : 1$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
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 $\displaystyle {O}^{18}=18-8=10$

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

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

  1. $ _{92}^{235}{U}$
  2. $ _{92}^{238}{U}$
  3. $ _{93}^{239}{Np}$
  4. $ _{93}^{240}{Np}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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  $\displaystyle _{93}^{240}{Np}$ $\displaystyle =240-93=147$

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

The discovery of neutron came very late because:

  1. it is present in nucleus

  2. it is a fundamental particle

  3. it does not move

  4. it does not carry any charge
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $\text{D}$.

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

The mass of neutron is of the order of: 

  1. ${10}^{-27} kg$
  2. ${10}^{-26} kg$
  3. ${10}^{-25} kg$
  4. ${10}^{-24} kg$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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:

  1. $5.6 MeV$
  2. $56 MeV$
  3. $0.56 MeV$
  4. $560 MeV$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. its atomic mass

  2. its atomic number

  3. the chemical nature of the atom

  4. number of the electron also
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

What is the order of density of neutron?

  1. $10^3$ kg/cc
  2. $10^6$ kg/cc
  3. $10^{12}$ kg/cc
  4. $10^2$ kg/cc
Reveal answer Fill a bubble to check yourself
C Correct answer
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

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

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

  1. $A - Z$
  2. $A + Z$
  3. $Z - A$
  4. $\frac{Z}{A}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 = $Z-A$