Tag: structure of atoms

Questions Related to structure of atoms

Number of neutrons present in $1.7$ g of ammonia is:

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

  1. $0.8N _A$

  2. $0.7N _A$

  3. $0.652N _A$

  4. $0.52N _A$

Show answer
Correct Option: B
Explanation:
Let us consider the problem.
For, moles of $N{H _3} = \frac{{1.7}}{{17}} = 0.1$
Let the Neutrons in 1 molecules of $N{H _3} = 7 + 3 \times 0 = 7$
Hence,
Number of Neurons $= 0.1 \times {N _A} \times 7$
The correct answer is $0.7{N _A}$

Calculate number of neutrons present in $12 \times 10^{25}$ atoms of oxygen $( _8O^{17})$:
(Given : N$ _A = 6 \times 10^{23}$)

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

  1. $1800$

  2. $1600$

  3. $1800\ N _A$

  4. $3200\ N _A$

Show answer
Correct Option: C
Explanation:

Atomic number =$ P =8$ 


Atomic Mass =$ N+P=17$


                         $N=9$
 Total no. of Neutrons = $9\times 12\times 10^{25}$

                                     =$\dfrac{9\times 12\times 10^{25}\times N _{A}}{6\times 10^{23}}$ 

                                 $=1800N _{A}$

Hence, the correct option is C.

The charge to mass ratio is highest for:

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

  1. proton

  2. electron

  3. neutron

  4. alpha

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Correct Option: B
Explanation:

The charge to mass ratio is highest for electron.
Charge/mass for :
$neutron=0/1=0, : \ $

$alpha=2/4=0.5, :$ 
$p=1/1= 1 \text { and,  }$
$ e=\dfrac {1}{1/1837}=1837$

Identify the sub-atomic particle with no charge and unit mass.

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

  1. Proton

  2. Electron

  3. Neutron

  4. All

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Correct Option: C
Explanation:

Proton have a positive charge and mass equal to one.
neutron have a zero charge and mass equal to one.
Electron have a negative charge and mass equal to 1/1840.

The heaviest subatomic particle is :

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

  1. neutron

  2. positron

  3. electron

  4. proton

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Correct Option: A
Explanation:

Neutron is heaviest subatomic particle among the given subatomic particles with mass of 1.008 amu while proton have mass of 1 amu.

The lightest particle is/are :

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

  1. electron

  2. proton

  3. neutron

  4. $\beta$-particle

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Correct Option: A,D
Explanation:
The electron is the lightest particle of the atom. It has a mass of $ 9.1 \times 10^{-28}$ grams. Comparing this mass to that of the proton's at $1.6726 \times 10^{-24}$ grams, an electron is nearly $0.0005$ times the proton's mass.

Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei. Hence, their mass will similar to that of the electron.

Hence, options A and D are correct.
State whether true or false :

A neutron can be found in all atoms.
chemistry structure of the atom neutrons discovery of neutrons structure of atoms

  1. True

  2. False

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Correct Option: B
Explanation:

The statement, 'Neutron can be found in all atoms' is false.


Neutron is absent in hydrogen atoms. 

The nucleus of $ _1^1H$ contains only a proton. 

So it is not necessary that all atoms have neutron in them.

Assertion : Protons are better projectiles than neutrons.
Reason : The neurons being neutral do not experience repulsion from positively charged nucleus.

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

  1. If both (A) and (R) are correct, and (R) is the correct explanation of (A).

  2. If both (A) and (R) are correct, but (R) is not the correct explanation of (A).

  3. If (A) is correct, but (R) is correct.

  4. If (A) is incorrect, but (R) is correct.

  5. If both (A) and (R) are incorrect.

Show answer
Correct Option: D
Explanation:

Neutrons are better projectiles than protons.
The decreasing order of the projectile power is $\displaystyle _0n^1 > _{1}H^{1} > _{1}H^{2}> _{2}He^{4}$
The neurons being neutral do not experience repulsion from positively charged nucleus.
Thus, (A) is incorrect, but (R) is correct.

Arrange the following particle in increasing order of values of e/m ratio : electron (e), proton (p), neutron (n) and $\displaystyle \alpha $-particle $\displaystyle (\alpha) $.

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

  1. n, p, e, $\displaystyle \alpha $

  2. n, $\displaystyle \alpha $, p, e

  3. n, p, $\displaystyle \alpha $, e

  4. e, p, n, $\displaystyle \alpha $

Show answer
Correct Option: B
Explanation:

$\displaystyle n< \alpha < p< e$            

e/m of n = 0
$\displaystyle e/m: : of: : \alpha =\frac{9.58\times 10^{4}}{2}c/g$
e/m of p = $\displaystyle 9.58\times 10^{4}: : c/g$
e/m of e = $\displaystyle 1.7588\times 10^{8}: : c/g$

Which of the following has the greatest mass?

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

  1. Electron

  2. Proton

  3. Neutron

  4. Hydrogen cation

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Correct Option: C
Explanation:

Neutron has greatest mass. Proton is a subatomic particle with symbol p and positive electric charge of +1 elementary charge and mass slightly less than that of neutron. Mass of neutron is $1.6749\times10^{-27}  kg$.