Chemistry · Physics

Atomic Structure and Mass

277 Questions

Atomic structure and mass focus on the composition of atoms, including protons, neutrons, electrons, and isotopes. This topic is essential for the chemistry sections in engineering and civil services competitive exams. Review these questions to practice calculating atomic mass, neutron count, and isotopic distributions.

Atomic mass unit calculationsNeutron and proton countsIsotopic distribution averagesLaw of triadsRest energy of atoms

Atomic Structure and Mass Questions

Multiple choice biomacromolecules biotechnology cell biology and biotechnology biomolecules biology

About 98 percentage of the mass of every living organism is composed of just six elements including carbon, hydrogen, nitrogen, oxygen and

  1. Sulphur and Magnesium

  2. Magnesium and Phosphorous

  3. Calcium and Phosphorous

  4. Phosphorus and Sulphur
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Body needs phosphorus to build and repair bones and teeth.
  • It also helps nerves to function.
  • Calcium is important on blood clotting, muscle contraction, and strengthening bones. 
Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

The relative atomic mass of $N$ and relative molecular mass of $N _2$ are:

  1. $14, 28$
  2. $7, 14$
  3. $14, 14$
  4. $7, 28$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Relative atomic mass is the ratio of the average mass of one atom of an element to one-twelfth of the mass of an atom of carbon-12.

The relative atomic mass of N is 14  and relative molecular mass of $N _2$ is 28.

Hence, option A is correct.
Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

The element chlorine consists of mixture of 75.53% $ _{17}$Cl$^{35}$ and 24.47% $ _{17}$Cl$^{37}$ having a mass of 34.97 amu and 36.95 amu, respectively. The atomic weight of chloride is:

  1. 35.25

  2. 35.45

  3. 36.25

  4. 36.45
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given - $ _{17} Cl^{35} - 75.53$% and mass of $Cl$ 34.97 amu
$ _{17} C^{37} - 24.47$% and mass of $Cl$ 36.95 amu
$\therefore $ Atomic weight of chlorine
$= \displaystyle \frac{(75.53 \times 34.97)+(24.47 \times 36.95)}{100} = \frac{3545.45}{100}$
$=35.45$

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

What was the need for using relative atomic mass or relative molecular mass?

  1. To round off every atomic mass as a multiple of 2

  2. To create new terminologies

  3. As the mass of atoms or molecules were small

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative atomic mass or relative molecular mass was used as the mass of the atoms or molecules were very small. Therefore there was a need to be taken relative to some other elements.

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

The atomic mass of sodium is 23. The gram-atomic mass of sodium is _______.

  1. 23 g

  2. 46 g

  3. 42 g

  4. 11.5 g
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gram atomic mass is the mass, in grams, of one mole of atoms in a monoatomic chemical element. It is numerically equal to the relative atomic mass in grams. The atomic mass of an element expressed in grams is called gram atomic mass.

$\therefore$  gram atomic mass of sodium $=23gm$

Multiple choice chemistry quantitative chemistry molecular mass relative formula mass masses of atoms and molecules

How many gram atoms are present in $256 g$ of ${ O } _{ 2 }$?

  1. $16$ gram atoms
  2. $32$ gram atoms
  3. $14$ gram atoms
  4. $36$ gram atoms
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given that, 
Mass of $O _2$ = 256 g


We know that, 
Number of moles = $[{Mass/Molar mass}]$

So, 
Moles of $O _2$ = $\dfrac {256}{32} =8$ 


Number of gram atoms = Number of moles$*$Numer of atoms 

                                        = $8 \times 2=16$ gram atoms 

Thus, option A is the correct answer.

Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

Mass numbers of the elements A, B, C and D are 30, 60, 90 and 120 respectively. the  specific binding energy of them are 5 MeV, 8.5 MeV, 8 MeV and 7 MeV respectively. then, in which of the following reaction/s energy is released?
(1) $ D \rightarrow 2B $
(2) $ C \rightarrow B+A $
(3) $ B \rightarrow 2A $

  1. only in (1)

  2. in(2), (3)

  3. in (1), (3)

  4. in (1), (2) and (3)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy is released when the product has a higher specific binding energy than the reactants. (1) D(7 MeV) -> 2B(8.5 MeV): 8.5 > 7, so energy is released. (2) C(8 MeV) -> B(8.5 MeV) + A(5 MeV): Average BE is (8.5+5)/2 = 6.75 < 8, so energy is absorbed. (3) B(8.5 MeV) -> 2A(5 MeV): 5 < 8.5, so energy is absorbed.

Multiple choice chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

If number of electrons in an atom is 8 and number of protons is also 8, then give the atomic number of atom and the charge on the atom.

  1. (i) Atomic number = 8, (ii) Charge = 0

  2. (i) Atomic number = 4, (ii) Charge = 0

  3. (i) Atomic number = 8, (ii) Charge = +1

  4. (i) Atomic number = 4, (ii) Charge = +1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Atomic number is equal to number of protons i.e. 8. Since number of protons is equal to number of electrons i.e. 8, therefore charge on the atom is 0.