Introduction to Structure of Atom

The Structure of Atom is one of the most important chapters in NEET Chemistry. It explains the basic building blocks of matter and their arrangements. Understanding this chapter is crucial for Physical Chemistry as well as for solving numerical problems related to atomic properties.

This chapter mainly focuses on atomic models, quantum numbers, electron configuration, and formulas related to energy and orbitals.

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♦ Some Basic Concepts of Chemistry ⇒ Download Now

♦ Structure of Atom ⇒ Download Now

♦ Classification of Elements and Periodicity in Properties ⇒ Download Now

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♦ s-Block Elements (Alkali and Alkaline Earth Metals) ⇒ Download Now

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♦ Some Basic Principles and Techniques ⇒ Download Now

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♦ Electrochemistry ⇒ Download Now

♦ Chemical Kinetics ⇒ Download Now

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♦ General Principles and Processes of Isolation of Elements ⇒ Download Now

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Importance of Structure of Atom for NEET

• Forms the foundation of Physical Chemistry

• Helps in understanding chemical bonding and periodicity

• NEET frequently asks conceptual and numerical questions

• Knowledge of formulas improves problem-solving speed

A strong grasp of formulas ensures accuracy and time-saving during exams.

Atomic Models

NEET often requires understanding different atomic models.

1. Dalton’s Atomic Theory

• Atom is indivisible, indestructible, and the smallest particle of matter.

• Mass is conserved in reactions.

2. Thomson’s Model (Plum Pudding Model)

• Atom is a positively charged sphere with embedded electrons.

3. Rutherford’s Model

• Atom has a dense positive nucleus.

• Electrons revolve around the nucleus.

4. Bohr’s Model

• Electrons revolve in fixed circular orbits (energy levels).

• Energy formula: Eₙ = - (2.18 × 10⁻¹⁸ J) × Z² / n²

  • Z = atomic number, n = orbit number

NEET Tip: Bohr’s model formulas are frequently asked for energy levels, radius, and ionization energy.

Bohr’s Radius Formula

Formula:
rₙ = n² × h² / (4π² × m × e² × Z)

• rₙ = radius of nth orbit

• h = Planck’s constant

• m = electron mass

• e = electron charge

• Z = atomic number

This is used in questions about orbit radius and electron positions.

Energy of Electron in nth Orbit

Formula:
Eₙ = - (13.6 eV) × Z² / n²

This formula calculates energy levels for hydrogen-like atoms.

Quantum Numbers

Quantum numbers define electron positions in an atom.

1. Principal Quantum Number (n):

• Energy level, n = 1, 2, 3…

2. Azimuthal Quantum Number (l):

• Sublevel shape: l = 0 to (n-1)

• 0 = s, 1 = p, 2 = d, 3 = f

3. Magnetic Quantum Number (mₗ):

• Orientation of orbital: mₗ = -l to +l

4. Spin Quantum Number (mₛ):

• Spin of electron: +½ or -½

NEET Tip: Quantum numbers are frequently asked in electron configuration and orbital problems.

Electron Configuration Formulas

• Aufbau Principle: Electrons fill lowest energy levels first

• Pauli Exclusion Principle: No two electrons have same set of quantum numbers

• Hund’s Rule: Maximum unpaired electrons in degenerate orbitals

Examples:

• Oxygen (Z=8): 1s² 2s² 2p⁴

• Sodium (Z=11): 1s² 2s² 2p⁶ 3s¹

Maximum Number of Electrons in an Orbit

Formula:
Maximum electrons in nth shell = 2n²

This formula helps calculate electron distribution in shells.

Radius of Hydrogen Atom (Bohr’s Model)

Formula:
rₙ = n² × a₀ / Z

• a₀ = Bohr radius = 0.529 Å

NEET Tip: Questions often ask first orbit radius of hydrogen or hydrogen-like ions.

Energy Difference Between Two Orbits

Formula:
ΔE = E_final – E_initial = 13.6 Z² (1/n₁² – 1/n₂²) eV

Used to calculate photon emission or absorption.

Effective Nuclear Charge (Z_eff)

Formula:
Z_eff = Z – S

• Z = actual nuclear charge

• S = shielding constant

This is important for periodic property calculations.

Electromagnetic Radiation and Atom

Planck’s Equation:
E = hν

• h = Planck’s constant

• ν = frequency

Relation to wavelength:
c = λν → E = hc / λ

• c = speed of light

• λ = wavelength

This formula is used in photoelectric effect and spectral line problems.

Rydberg Formula for Spectral Lines

Formula:
1/λ = R_H (1/n₁² – 1/n₂²)

• R_H = Rydberg constant = 1.097 × 10⁷ m⁻¹

• n₂ > n₁

This formula calculates hydrogen emission spectrum, a frequently asked NEET question.

Important Constants for NEET

• h (Planck’s constant) = 6.626 × 10⁻³⁴ J·s

• c (speed of light) = 3 × 10⁸ m/s

• R_H (Rydberg constant) = 1.097 × 10⁷ m⁻¹

• e (electron charge) = 1.602 × 10⁻¹⁹ C

• m_e (electron mass) = 9.109 × 10⁻³¹ kg

Memorizing constants ensures quick calculations in exams.

Conclusion

Structure of Atom is a scoring chapter for NEET Chemistry. Mastery of formulas related to Bohr’s model, energy levels, quantum numbers, electron configuration, and spectral lines is crucial.

• Helps in solving numerical problems quickly

• Provides conceptual clarity for Periodic Table and Chemical Bonding

• Essential for understanding Photoelectric effect, Hydrogen spectrum, and Atomic properties

Students should practice formulas regularly and solve related numerical questions to maximize NEET scores.

For more NEET Chemistry formulas, notes, and problem-solving tips, visit StudentBro.in, your trusted platform for exam success.