Tag: discovery of subatomic particles

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

What are nucleons?

  1. the sum of protons and neutrons present in the nucleus.

  2. the number of protons in the nucleus.

  3. the number of neutrons in the nucleus.

  4. the sum of protons, neutrons and electrons present in the nucleus.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A nucleon is one of either of the two types of subatomic particles (neutrons and protons) which are located in the nucleus of atoms.
Only option A correct .

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

Find the mass number of sodium having $12$ neutrons.

  1. $22$
  2. $23$
  3. $11$
  4. $12$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The atomic weight is basically a measurement of the total number of particles in an atom's nucleus. Mass number can be found by rounding off an elements atomic mass to the nearest whole number.
Mass Number $=$ (Number of Protons) $+$ (Number of Neutrons)
$= 11 + 12$
$= 23$

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

The number of protons is equal to ________ in a neutral atom.

  1. atomic weight

  2. atomic number

  3. number of electrons

  4. both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The atomic number is the number of protons in an atom of an element. Atoms are electrically neutral. That means that there must be a balance between the positively charged protons and the negatively charged electrons.


Thus, atoms must have equal numbers of protons and electrons.


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

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

The mass of electron, proton and neutron in grams are :

  1. $1.108\times 10^{-28}, 1.6726\times 10^{-24}, 1.675 \times 10^{-24}$
  2. $9.108\times 10^{28}, 1.6726\times 10^{24}, 1.675 \times 10^{24}$
  3. $9.108\times 10^{-24}, 1.6726\times 10^{-24}, 1.675 \times 10^{24}$
  4. $9.108\times 10^{-28}, 1.6726\times 10^{-24}, 1.675 \times 10^{-24}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An electron is a tiny particle with a mass of $9.108\times 10^{-28}$ g and a negative charge. All neutral atoms contain electrons. The mass of a proton is $1.6726\times 10^{-24}$ g, or about 1836 times the mass of an electron. The proton carries a positive electrical charge, that is equal in magnitude to the charge of the electron but opposite in sign. Mass of a neutron is $1.675 \times  10^{-24}$ g. It is very close to that of the proton. A neutron carries no charge.

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

Find the number of neutrons in silver having atomic mass of $107.86$.

  1. $65$
  2. $71$
  3. $61$
  4. $47$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The atomic weight is basically a measurement of the total number of particles in an atom's nucleus. Mass number can be found by rounding off an elements atomic mass to the nearest whole number.
$Mass\ Number = (Number\ of\ protons) + (Number\ of\ neutrons)$
Number of neutrons $= mass\ number- number\ of\ protons$
Atomic mass of silver $= 107.86$
Mass number $= 108$
Number of protons $= 47$
Number of neutrons $= 108 - 47$
$= 61$
$\therefore$ Number of neutrons in a silver $=61$

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

 How many moles of electron weighs one kilogram?

  1. $6.023 \times 10^{23}$
  2. $\dfrac{1}{9.108} \times 10^{32}$
  3. $\dfrac{6.023}{9.108} \times 10^{54}$
  4. $\dfrac{1}{9.108 \times 6.023} \times 10^{8}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Mass of one electron $ \displaystyle =9.108 \times 10^{-31}$ kg.

Mass of one mole of electrons $ \displaystyle =9.108 \times 10^{-31} \times 6.023 \times 10^{23}=9.108   \times 6.023 \times 10^{-8}$ kg.

The number of moles of electrons that weigh one kilogram $ \displaystyle = \dfrac {1}{9.108   \times 6.023 \times 10^{-8}}= \dfrac {1}{9.108   \times 6.023}  \times 10^{8}$

Hence, the correct option is $D$
Multiple choice chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

Positronium is the name given to an atom-like combination formed between_____________.

  1. a positron and a proton

  2. a positron and a neutron
  3. a positron and an $\alpha$-particle

  4. a positron and an electron
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Positronium is the name given to an atom-like combination formed between a positron and an electron. Electron  and positron are particle and antiparticle.

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

If $N _A$ is the Avogadro's number then number of valence electrons in 4.8 g of $O^{2-} $ is:

  1. $2.4\, N _A$
  2. $4.2\, N _A$
  3. $1.6\, N _A$
  4. $3.2\, N _A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Number of mole in 4.8 gm of oxygen atom $=\dfrac{4.8}{16} = 0.3$ mole 

Number of the valence electron in one ion of $O^{2-} = 8$

Number of the valence electron in 0.3 mole of $O^{2-} = 8\times0.3\times N _A =2.4N _A$

Hence, the correct option is $(A)$.
Multiple choice chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

Mass of 1 mole neutrons $(m _n= 1.675 \times 10^{-27}\, kg)$ is:

  1. $1.8 \times 10^{-3}\, kg$
  2. $1.008 \times 10^{-4}\, kg$
  3. $1.08 \times 10^{-3}\, kg$
  4. $1.008 \times 10^{-3}\, kg$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mass of one neutron $= 1.675 \times 10^{-27}$ kg


1 mole contains $6.02 \times 10^{23}$ neutrons

mass of 1 mole neutrons $= 1.675 \times 6.02 \times  10^{-27} \times 10^{23}$

                                         $=1.008 \times 10^{-3}$ kg