CBSE Chemistry: Calculate Electrons, Neutrons and Protons in CH₄, ¹⁴C and NH₃

 - Dr.Sanjaykumar Pawar  

Short Notes: Mole Concept, Electrons, Protons and Neutrons 

Step-by-step CBSE Chemistry calculations for electrons, neutrons and protons using Avogadro's number.

1. Avogadro Number (Nₐ)

• 1 mole of any substance contains 6.022 × 10²³ particles.
• It may represent atoms, molecules, ions, electrons, etc.

Memory Trick:
1 Mole = 6.022 × 10²³

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2. Electrons in Methane (CH₄)

Composition

• Carbon (C) = 6 electrons
• Hydrogen (H) = 1 electron

For CH₄:

Total electrons = 6 + 4(1)

= 10 electrons per molecule

In One Mole of CH₄

Total electrons

= 10 × 6.022 × 10²³

= 6.022 × 10²⁴ electrons

Shortcut:
CH₄ → 10 electrons

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3. Neutrons in Carbon-14 (¹⁴C)

Formula

Number of Neutrons

= Mass Number − Atomic Number

For ¹⁴C

Mass Number = 14

Atomic Number = 6

Neutrons = 14 − 6

= 8 neutrons per atom

Shortcut:
¹⁴C → 8 neutrons

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4. Protons in Ammonia (NH₃)

Composition

Nitrogen = 7 protons

Hydrogen = 1 proton

For NH₃:

Total protons

= 7 + 3(1)

= 10 protons per molecule

Shortcut:
NH₃ → 10 protons

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5. Mass of Subatomic Particles

Particle	Mass
Proton	1.67 × 10⁻²⁷ kg
Neutron	1.675 × 10⁻²⁷ kg

Formula

Total Mass

= Number of Particles × Mass of One Particle

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6. Important Formulas

Number of Particles

Number of particles

= (Given Mass / Molar Mass) × Nₐ

Total Electrons

= Number of Molecules × Electrons per Molecule

Total Protons

= Number of Molecules × Protons per Molecule

Total Neutrons

= Number of Atoms × Neutrons per Atom

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7. Effect of Temperature and Pressure

• Temperature and Pressure affect only the volume of a gas.
• They do not affect:
  • Number of molecules
  • Number of protons
  • Number of electrons
  • Number of neutrons
  • Total mass

NEET Fact:
Particle count remains constant if the amount of substance remains the same.

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One-Line Revision

✓ CH₄ → 10 electrons

✓ NH₃ → 10 protons

✓ ¹⁴C → 8 neutrons

✓ 1 Mole → 6.022 × 10²³ particles

✓ Particle Mass = Number × Individual Mass

✓ Temperature & Pressure change volume only, not particle count. 

NEET Practice Questions

Topic: Mole Concept, Electrons, Protons & Neutrons

Section A: Concept-Based MCQs

Q1.

The total number of electrons present in one molecule of CH₄ is:

(A) 8
(B) 10
(C) 12
(D) 14

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Q2.

The number of neutrons present in one atom of ¹⁴C is:

(A) 6
(B) 8
(C) 14
(D) 20

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Q3.

The total number of protons present in one molecule of NH₃ is:

(A) 7
(B) 8
(C) 10
(D) 17

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Q4.

One mole of methane contains:

(A) 6.022 × 10²³ electrons

(B) 6.022 × 10²⁴ electrons

(C) 12.044 × 10²³ electrons

(D) 3.011 × 10²³ electrons

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Q5.

The value of Avogadro Number is:

(A) 6.022 × 10²¹

(B) 6.022 × 10²²

(C) 6.022 × 10²³

(D) 6.022 × 10²⁴

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Section B: Numerical Based Questions

Q6.

Calculate the total number of electrons present in 2 moles of CH₄.

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Q7.

Find the total number of protons present in 17 g of NH₃.

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Q8.

Calculate the number of neutrons present in 14 g of ¹⁴C.

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Q9.

Calculate the mass of all protons present in 34 g of NH₃.

(Mass of one proton = 1.67 × 10⁻²⁷ kg)

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Q10.

How many neutrons are present in 28 mg of ¹⁴C?

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Section C: Assertion & Reason

Q11.

Assertion (A): Temperature and pressure do not affect the number of protons in NH₃.

Reason (R): Temperature and pressure only affect the volume of a gas.

(A) Both A and R are true and R is the correct explanation.

(B) Both A and R are true but R is not the correct explanation.

(C) A is true but R is false.

(D) A is false but R is true.

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Q12.

Assertion (A): One molecule of NH₃ contains 10 protons.

Reason (R): Nitrogen contributes 7 protons and three hydrogen atoms contribute 3 protons.

(A) Both A and R are true and R is the correct explanation.

(B) Both A and R are true but R is not the correct explanation.

(C) A is true but R is false.

(D) A is false but R is true.

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Section D: NEET Trick Questions

Q13.

Which of the following contains the greatest number of electrons?

(A) 1 mole CH₄

(B) 1 mole NH₃

(C) 1 mole H₂

(D) 1 mole He

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Q14.

The ratio of total electrons in one molecule of CH₄ to total protons in one molecule of NH₃ is:

(A) 1 : 1

(B) 2 : 1

(C) 1 : 2

(D) 5 : 3

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Q15.

If the volume of NH₃ gas is doubled by increasing temperature, the total number of protons will:

(A) Double

(B) Become half

(C) Remain unchanged

(D) Become zero

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Section E: Previous Year Style Questions

Q16.

How many molecules are present in 8.5 g of NH₃?

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Q17.

Calculate the total number of electrons present in 0.5 mole of CH₄.

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Q18.

Find the total mass of neutrons present in 7 mg of ¹⁴C.

(Mass of one neutron = 1.675 × 10⁻²⁷ kg)

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Q19.

A sample contains 1.2044 × 10²² protons. Identify the mass of NH₃ present.

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Q20.

Calculate the number of neutrons present in 0.25 mole of ¹⁴C.

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Answer Key

1. B
2. B
3. C
4. B
5. C
6. 1.2044 × 10²⁵ electrons
7. 6.022 × 10²⁴ protons
8. 4.8176 × 10²⁴ neutrons
9. 2.01 × 10⁻² g (approximately)
10. 9.6352 × 10²¹ neutrons
11. A
12. A
13. A
14. A
15. C
16. 3.011 × 10²³ molecules
17. 3.011 × 10²⁴ electrons
18. 4.03 × 10⁻⁶ kg
19. 34 mg NH₃
20. 1.2044 × 10²⁴ neutrons 

 Internal Links

Mole Concept Formula Sheet for CBSE

Avogadro Number Explained with Examples

Atomic Structure Numerical Problems

Mass Number and Atomic Number Questions

Calculation of Moles, Atoms and Molecules

Isotopes and Isobars Explained

Class 11 Chemistry Chapter 1 Notes

Important CBSE Chemistry Numericals with Solutions

Structure of Atom MCQs and Answers

Previous Year CBSE Chemistry Questions

CBSE Chemistry Numerical Questions and Answers

Q.2. (i) Calculate the total number of electrons present in one mole of methane.

(ii) Find: (a) the total number and (b) the total mass of neutrons in 7 mg of ¹⁴C. (Assume that mass of a neutron = 1.675 × 10⁻²⁷ kg).

(iii) Find: (a) the total number and (b) the total mass of protons in 34 mg of NH₃ at STP. Will the answer change if the temperature and pressure are changed?

Answer:

(i) Total Number of Electrons in One Mole of Methane

One molecule of methane (CH₄) contains:

• Carbon = 6 electrons
• Hydrogen = 4 × 1 = 4 electrons

Total electrons in one molecule of CH₄ = 6 + 4 = 10

Since 1 mole contains 6.022 × 10²³ molecules,

Total electrons = 10 × 6.022 × 10²³

= 6.022 × 10²⁴ electrons

Answer: 6.022 × 10²⁴ electrons

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(ii) Total Number and Mass of Neutrons in 7 mg of ¹⁴C

(a) Total Number of Neutrons

For ¹⁴C:

• Mass number = 14
• Atomic number = 6

Number of neutrons per atom = 14 − 6 = 8

14 g (14000 mg) of ¹⁴C contain 6.022 × 10²³ atoms.

Therefore, 7 mg of ¹⁴C contain:

(7 / 14000) × 6.022 × 10²³

= 3.011 × 10²⁰ atoms

Total neutrons = 3.011 × 10²⁰ × 8

= 2.4088 × 10²¹ neutrons

Answer: 2.4088 × 10²¹ neutrons

(b) Total Mass of Neutrons

Mass of one neutron = 1.675 × 10⁻²⁷ kg

Mass of 2.4088 × 10²¹ neutrons

= (2.4088 × 10²¹) × (1.675 × 10⁻²⁷)

= 4.03 × 10⁻⁶ kg

Answer: 4.03 × 10⁻⁶ kg

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(iii) Total Number and Mass of Protons in 34 mg of NH₃

Step I: Calculation of Number of NH₃ Molecules

Molar mass of NH₃ = 17 g = 17000 mg

17000 mg of NH₃ contain 6.022 × 10²³ molecules.

34 mg of NH₃ contain:

(34 / 17000) × 6.022 × 10²³

= 1.2044 × 10²¹ molecules

Step II: Calculation of Number of Protons

One molecule of NH₃ contains:

• Nitrogen = 7 protons
• Hydrogen = 3 × 1 = 3 protons

Total protons per molecule = 10

Total protons = 1.2044 × 10²¹ × 10

= 1.2044 × 10²² protons

Answer: 1.2044 × 10²² protons

Step III: Calculation of Mass of Protons

Mass of one proton = 1.67 × 10⁻²⁷ kg

Mass of protons

= (1.2044 × 10²²) × (1.67 × 10⁻²⁷)

= 2.01 × 10⁻⁵ kg

Answer: 2.01 × 10⁻⁵ kg

Will the Answer Change if Temperature and Pressure are Changed?

No, the answer will not change with temperature and pressure because the number of protons and their total mass depend only on the amount of NH₃ present. Temperature and pressure can change the volume occupied by the gas, but not the number of molecules, protons, or their mass.

NEET Chemistry Smart Revision Sheet

Question

(i) Calculate the total number of electrons present in one mole of methane (CH₄).

(ii) Find:
(a) the total number and
(b) the total mass of neutrons in 7 mg of ¹⁴C.
(Assume that mass of one neutron = 1.675 × 10⁻²⁷ kg)

(iii) Find:
(a) the total number and
(b) the total mass of protons in 34 mg of NH₃ at STP.

Will the answer change if the temperature and pressure are changed?

Topper Solution

(i) Total Electrons in One Mole of CH₄

Carbon = 6 electrons
Hydrogen = 4 × 1 = 4 electrons

Total electrons per molecule = 10

1 mole contains:

6.022 × 10²³ molecules

Therefore,

Total electrons = 10 × 6.022 × 10²³

= 6.022 × 10²⁴ electrons

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(ii) Neutrons in 7 mg of ¹⁴C

Mass Number = 14
Atomic Number = 6

Neutrons = 14 − 6 = 8

14 g = 14000 mg contain 6.022 × 10²³ atoms

7 mg contain:

(7/14000) × 6.022 × 10²³

= 3.011 × 10²⁰ atoms

Total neutrons:

3.011 × 10²⁰ × 8

= 2.4088 × 10²¹ neutrons

Mass of neutrons:

2.4088 × 10²¹ × 1.675 × 10⁻²⁷

= 4.03 × 10⁻⁶ kg

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(iii) Protons in 34 mg NH₃

Molar mass NH₃ = 17 g = 17000 mg

34 mg contain:

(34/17000) × 6.022 × 10²³

= 1.2044 × 10²¹ molecules

Protons per NH₃ molecule:

Nitrogen = 7
Hydrogen = 3
Total = 10

Total protons:

1.2044 × 10²¹ × 10

= 1.2044 × 10²² protons

Mass of protons:

1.2044 × 10²² × 1.67 × 10⁻²⁷

= 2.01 × 10⁻⁵ kg

Temperature and pressure change only volume.
Number of particles remains unchanged.

Master Memory Table

Compound	Key Value	Instant Recall
CH₄	10 Electrons	6 + 4 = 10
NH₃	10 Protons	7 + 3 = 10
¹⁴C	8 Neutrons	14 − 6 = 8
1 Mole	6.022 × 10²³	Avogadro Number
Proton Mass	1.67 × 10⁻²⁷ kg	P = 1.67
Neutron Mass	1.675 × 10⁻²⁷ kg	N = 1.675

Mnemonic Section

CH₄ Mnemonic

"Carbon Six, Hydrogen Four"

6 + 4 = 10 Electrons

NH₃ Mnemonic

"Nitrogen Seven, Three Hydrogens"

7 + 3 = 10 Protons

¹⁴C Mnemonic

"14 का घर, 6 का दरवाज़ा, अंदर बैठे 8 नवाब"

14 − 6 = 8 Neutrons

NEET Exam Traps

Trap 1

CH₄ has 10 electrons.

Do NOT write only Avogadro Number.

Correct: 10 × N_A

Trap 2

In ¹⁴C,

Neutrons ≠ 14

Correct: 14 − 6 = 8

Trap 3

Changing Temperature and Pressure does NOT change number of particles.

Only volume changes.

5-Second NEET Hacks

• CH₄ → 10 Electrons
• NH₃ → 10 Protons
• ¹⁴C → 8 Neutrons
• 1 Mole → 6.022 × 10²³
• Particle Mass = Number × Individual Mass
• T & P affect Volume only

One-Line Final Revision

CH₄ → 10 Electrons
NH₃ → 10 Protons
¹⁴C → 8 Neutrons
1 Mole → 6.022 × 10²³ Particles
Particle Mass = Number × Individual Mass
Temperature & Pressure affect volume only.