Atomic Structure FULL CHAPTER | Class 11th Physical Chemistry | Chapter 2 | Arjuna JEE

Arjuna JEE180 minutes read

The text explains the structure of an atom, focusing on electron distribution and orbital filling, detailing the properties and discovery of subatomic particles like electrons, protons, and neutrons. It also highlights key concepts such as atomic models by Thomson and Rutherford, the electromagnetic spectrum, quantum theory, and important formulas for calculating various atomic properties, emphasizing the dual nature of electrons and principles like Heisenberg's uncertainty principle and quantum numbers.

Insights

  • Electrons are arranged in orbitals based on energy levels, with increasing order of energy.
  • Thomson's experiment with a cathode ray tube led to the discovery of electrons and their properties.
  • The concept of isotopes, isotones, and isoelectronic species is integral to understanding atomic structure.
  • The Planck constant and quantum theory explain energy absorption and emission through photons.
  • De Broglie's theory highlights the dual nature of particles and electromagnetic radiation.
  • Quantum numbers provide detailed information about electron properties, while the Heisenberg uncertainty principle limits precise electron position determination.

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Recent questions

  • What is the significance of the Heisenberg uncertainty principle?

    The Heisenberg uncertainty principle highlights the fundamental limitation in determining both the position and velocity of microscopic particles like electrons with absolute precision. This principle asserts that the more accurately you know one of these properties, the less accurately you can know the other. It underscores the inherent uncertainty in the behavior of particles at the quantum level, emphasizing the dual nature of particles as both waves and particles. This principle has profound implications in quantum mechanics, shaping our understanding of the behavior of subatomic particles and the probabilistic nature of their existence.

  • How do electrons fill orbitals in an atom?

    Electrons fill orbitals in an atom following specific rules known as the Offbio Principal, Pauli Exclusion Principle, and Hans' Rule of Maximum Multiplicity. The Offbio Principal dictates that electrons occupy orbitals in increasing order of energy. The Pauli Exclusion Principle states that no two electrons in a given orbital can have the same spin, necessitating opposite spins for paired electrons. Hans' Rule of Maximum Multiplicity guides the filling of degenerate orbitals, where electrons fill them one by one before pairing up. These rules govern the electron configuration of atoms, ensuring stability and efficient distribution of electrons within the atom.

  • What is the concept of nodal planes in atomic orbitals?

    Nodal planes in atomic orbitals refer to regions where the probability of finding an electron is zero. These planes act as boundaries that separate regions of space where electrons are likely to be found from those where they cannot exist. The number of nodal planes varies depending on the type of orbital and its angular momentum quantum number. Understanding nodal planes is crucial in visualizing the distribution of electrons in different orbitals and comprehending the spatial arrangement of electron density within an atom. Nodal planes play a significant role in determining the shape and characteristics of atomic orbitals, influencing the behavior of electrons within the atom.

  • How does the Quantum Mechanical Model address the limitations of previous atomic models?

    The Quantum Mechanical Model overcomes the shortcomings of earlier atomic models by incorporating the wave-particle duality of electrons. Unlike classical models that viewed electrons as particles orbiting the nucleus in fixed paths, the Quantum Mechanical Model represents electrons as three-dimensional waves. This model accounts for the uncertainty in determining the exact position and velocity of electrons, as highlighted by the Heisenberg uncertainty principle. By treating electrons as waves with probabilistic behavior, the Quantum Mechanical Model provides a more accurate description of electron behavior within atoms, offering a comprehensive understanding of atomic structure and electron distribution.

  • What are the rules for determining the energy levels of atomic orbitals?

    The energy levels of atomic orbitals are determined by the principal quantum number (N) and the azimuthal quantum number (L). The N + L Rule, also known as the Bar Badi Rule, states that the sum of the principal quantum number and azimuthal quantum number leads to higher energy levels as the value increases. For example, comparing different orbitals based on their N and L values reveals a specific order of increasing energy levels. Understanding these rules is essential for predicting the relative energy levels of orbitals within an atom and comprehending the stability and arrangement of electrons in different atomic species.

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Summary

00:00

Atom Structure and Subatomic Particle Discovery.

  • The structure of an atom involves the probability of electron distribution in specific regions.
  • The size square value should be maximum for the region with the highest probability of electron presence.
  • Electrons are filed in orbitals in increasing order of energy.
  • The session focuses on completing the structure of the atom within a limited timeframe.
  • The discovery of subatomic particles, including electrons, protons, and neutrons, is discussed.
  • Thomson's experiment with a cathode ray tube led to the discovery of electrons.
  • The properties of cathode rays include traveling in a straight line and being deflected by electric fields.
  • The charge and mass of electrons are detailed, with a charge of -1.6 * 10^-19 coulombs and a mass of 9.1 * 10^-31 kg.
  • Protons, positively charged particles, are discussed in relation to different gases and their specific charges.
  • The properties of anode rays depend on the nature of the gas used in the experiment.

13:34

Atomic Models and Charge Discovery in Particles

  • Specific charge is the charge-to-mass ratio of particles like electrons and protons.
  • The discovery of the neutron was made by James Chadwick through bombarding beryllium with alpha particles.
  • Neutrons have a mass of 1.674 * 10^-27 kg and no charge.
  • Thomson's atomic model described atoms as spherical with uniform positive charge and distributed negative charge.
  • Thomson's model is also known as the Watermelon Model.
  • Rutherford's gold foil experiment showed that atoms have a small, dense nucleus with positive charge.
  • Most alpha particles passed through the gold foil, indicating a small positive charge area in the atom.
  • Rutherford named this small positive charge area the nucleus.
  • The volume of the nucleus is much smaller than the volume of the atom.
  • Rutherford's atomic model emphasized the small, positively charged nucleus within the atom.

28:42

Thomson's Missing Orbit: Atomic Model Mysteries

  • Thomson is missing, and his whereabouts are unknown.
  • Thomson is in charge of the nucleus and discusses the electrons revolving around it.
  • The circular lesson is named "Orbit" by Thomson.
  • The electron is described as the nucleus's brother, with attractions and centrifugal forces balancing its movement.
  • Thomson derived his atomic model from the continuous revolution of electrons.
  • The atomic model emphasizes the nucleus's small size, positive charge, and electron rotation.
  • Rutherford's atomic model fails to explain why electrons do not collapse into the nucleus.
  • The limitations of atomic models are discussed, focusing on the stability of the atom.
  • Atomic mass is calculated by adding the number of protons and neutrons.
  • Isotopes, isotones, and isoelectronic species are explained in relation to atomic structure.

45:02

"Electromagnetic Spectrum: Order, Wavelength, Frequency, Photons"

  • The electromagnetic spectrum is divided into different regions, including radio waves, microwaves, and infrared.
  • Understanding the order of the spectrum is crucial, starting from gamma rays and ending with radio waves.
  • Frequency decreases as you move along the spectrum, while wavelength increases.
  • Wavelength is the distance between two consecutive crests of electromagnetic radiation.
  • Frequency refers to the number of cycles per second completed by electromagnetic radiation.
  • The speed of light is represented by the symbol 'c' and is constant.
  • Planck's quantum theory explains how energy is absorbed and emitted in small packets called photons.
  • The energy of a photon is directly proportional to the frequency of light.
  • The Planck constant, denoted by 'h', is crucial in calculating the energy of photons.
  • Simple numerical questions based on these concepts are common in exams, emphasizing the importance of regular revision and practice.

59:27

Effective Study Habits and Photoelectric Effect

  • Backlogs can lead to a loss of confidence and differentiation from others.
  • Spending an hour daily on backlog management is crucial.
  • Consistent effort is necessary to avoid backlog accumulation.
  • Studying consistently for shorter durations is more effective than long hours.
  • Taking advantage of holidays for study is recommended.
  • The photoelectric effect involves ejecting electrons from a metal surface with light of specific frequency.
  • The minimum frequency required to eject electrons is the threshold frequency.
  • The number of photoelectrons ejected is proportional to light intensity, not frequency.
  • Kinetic energy of photoelectrons is directly proportional to light frequency.
  • Total energy from photons is used to eject electrons and convert excess energy into kinetic energy.

01:13:22

Relationship between light, electrons, and spectra explained.

  • The questions pertain to the relationship between incident light and electron rejection from a metal surface, focusing on kinetic energy and energy.
  • The graph depicting kinetic energy and intensity shows no relation, while the number of electrons with frequency remains constant.
  • The kinetic energy of the frequency graph does not start from zero, contrary to the assumption.
  • Continuous spectrum is characterized by a seamless transition between colors, unlike a discontinuous spectrum where colors merge.
  • Emission and absorption are two types of spectra, with emission lines indicating transitions between energy states in atoms.
  • The Balmer series in hydrogen's spectrum involves transitions from energy state 3 to 2, visible in the ultraviolet region.
  • The Bracket series follows the Balmer series, with transitions from energy state 4 to 2, extending into the infrared region.
  • The Lemon series signifies transitions from energy state 1 to infinity, with the first line representing the electron's return to the ground state.
  • Understanding the emission spectrum involves calculating wavelengths and energy transitions, with the Balmer series indicating transitions from higher to lower energy states.
  • Calculations in hydrogen's spectrum involve determining wavelengths and frequencies, with the visible region hosting the series.

01:30:37

Electron Orbits: Formulas and Energy Levels

  • 2π as an integral multiple will have a value of N as 1234 for orbital angular momentum, not 0.5.
  • The value of N must be a whole number, not 0.5, as per the postulate.
  • Formulas are derived for the radius, velocity, and energy of an electron in orbit.
  • The formula for radius is MR = Na/2π, and for velocity is 2.19 * 10 / n m per second.
  • The number of revolutions made by an electron in one second is directly proportional to n² / s.
  • The time taken for one revolution is n³ / z², directly proportional to the square.
  • The total energy of an electron is the sum of potential and kinetic energy, with potential energy being -13.6 * z² / n².
  • The formula for ionization energy is infinity from the first orbit to infinity, with energy at infinity being zero.
  • The formula for Seperation Energy is 13.6 * z² on Electron Volt.
  • The energy of different orbits increases as you move away from the nucleus, with gradual differences in energy between orbits.

01:44:25

Atomic Energy Formulas and Electron Behavior

  • The separation energy of an electron at infinity is calculated as zero minus 13.6 * z² / n².
  • The formula for energy in an atom is 13.6 * z² / n².
  • The maximum number of spectral lines formed during an electron transition is determined by the formula n2 - n1 * n2 - n1 +1/2.
  • The radius of the first orbit of a hydrogen atom is calculated as 0.59 * n²/s.
  • The formula for the radius of the second orbit of beryllium is 0.59 * 2².
  • The velocity of an electron in different orbits is inversely proportional to the square of the orbit number.
  • The formula for the shortest wavelength in a series is r z² / n1² - 1 / n2².
  • The energy of an electron transitioning from the ground state to the first excited state is calculated as -13.6 * z² / n².
  • The speed of an electron in different orbits is directly proportional to the square root of the orbit number.
  • Louis de Broglie proposed that electromagnetic radiation exhibits dual nature, showing both particle and wave characteristics.

01:57:30

De Broglie's Dual Nature Theory Formulas

  • De Broglie stated that particles, like peas, have dual nature, similar to electromagnetic radiation.
  • The formula derived from De Broglie's theory is λ = h/mc².
  • Another formula equates λ to h/p or h/√2m.
  • The formula for charged particles' kinetic energy is K*V.
  • The formula for gas molecules' wavelength is λ = h/√3mkt.
  • The temperature constant in the gas molecules' formula is 1.38 * 10^-23.
  • The formula for electrons' wavelength is λ = h/m, with specific values for h, m, and velocity.
  • The relationship between kinetic energy and De Broglie wavelength is inversely proportional to the square root of mass ratios.
  • A formula for calculating the wavelength of an electron accelerated through a potential difference is provided.
  • The relationship between the number of waves made by electrons in different orbits and the wavelength is expressed as 2πr n = nλ.

02:11:27

Quantum Model: Dual Nature of Electrons Explained

  • 2πr represents a specific distance in orbit, indicating the travel of a rectangle.
  • Lambda's equality signifies the distance traveled in orbit, with Lambda denoting the number of views.
  • The formula for Lambda is N lambda, where N represents the number of views.
  • Microscopic particles' mass and velocity uncertainty are inversely related.
  • De Broglie Wavelength is significant for microscopic particles like electrons, protons, and neutrons.
  • The Uncertainty Principle by Heisenberg highlights the impossibility of determining both position and velocity with 100% accuracy.
  • Uncertainty in position and velocity is crucial for microscopic particles' significant values.
  • The failure of the atomic model was due to not considering the dual nature of electrons.
  • The Quantum Mechanical Model accounts for the dual nature of electrons, incorporating wave-particle duality.
  • This model views electrons as 3D waves, representing a quantum mechanical approach.

02:28:02

Quantum Mechanics: Energy, Equations, and Electrons

  • The text discusses the concept of energy, velocity, and coordinates in a three-dimensional space.
  • It mentions the Vav equation, also known as the Schrödinger equation, which is fundamental in quantum mechanics.
  • The equation is crucial in determining the total energy of a system and is integral to the quantum mechanical model.
  • The text delves into the significance of the equation and its implications in quantum physics.
  • It introduces the concept of the wave function, which plays a vital role in understanding the behavior of electrons.
  • The text explores the Heisenberg uncertainty principle, highlighting the limitations in determining the exact position of electrons.
  • It discusses the probability density function and its role in predicting the likelihood of finding electrons in specific regions.
  • The text explains the concept of quantum numbers, which provide detailed information about the location and energy levels of electrons.
  • It elaborates on the principal quantum number, azimuthal quantum number, and magnetic quantum number, each contributing to defining the electron's properties.
  • The text concludes with a discussion on the maximum number of electrons in subshells and the formula for calculating orbital angular momentum.

02:43:25

"Electron Orbitals and Spin Values Explained"

  • If Sushel is present, three values of M are possible for him, ranging from -1 to +1, including zero.
  • These three values of M correspond to three orbitals.
  • The three orbitals are named P.C., P.A., and P.J.
  • The subshell value Lo indicates the subshell and subcell, determining the value of M.
  • For a value of Lo, five orbitals are possible, accommodating a total of 5 electrons.
  • F subshell with a value of 3 for L indicates M values from -3 to +3, allowing for 7 orbitals.
  • The spin of an electron can be defined as either plus half or minus half.
  • Each orbital can hold a maximum of 2 electrons with opposite spins.
  • S subshell contains one orbital, allowing for a maximum of 2 electrons.
  • P subshell has three orbitals, accommodating a total of 6 electrons.

02:59:00

Understanding Nodal Planes in Atomic Orbitals

  • Nodal plane concept discussed in relation to electron probability and angular mode
  • Explanation of nodal planes in relation to PC and electron distribution
  • Clarification on the number of nodal planes for different scenarios
  • Details on the formula for nodal planes and the significance of L in the formula
  • Explanation of radial nodes and the formula for radial node calculation
  • Clarification on the presence of angular nodes and their significance
  • Discussion on the presence of nodal planes in different orbitals like 2px, 3px, etc.
  • Explanation of the total number of nodes in different orbitals and the significance of radial and nodal nodes
  • Clarification on the presence of nodal planes in di orbitals and s orbitals
  • Details on the energy order of atomic orbitals based on the principal quantum number N and the number of electrons in the species

03:13:15

Orbital Energy Levels and Electron Configuration

  • Energy value after Beta depends on N and L values
  • N and L values determine energy levels
  • N + L Rule or Bar Badi Rule states higher N + L value leads to higher energy
  • Example: Comparing energy levels of orbitals based on N and L values
  • Order of increasing energy: 3s, 3d, 4f, 4p, 5s, 4d
  • N + L values determine orbital energy levels
  • Example: Comparing energy levels of different orbitals based on N values
  • Rules for electron filing: Offbio Principal, Pauli Exclusion Principle, Hans' Rule of Maximum Multiplicity
  • Offbio Principal: Electrons fill orbitals in increasing energy order
  • Pauli Exclusion Principle: Two electrons in a vital must have opposite spins
  • Hans' Rule of Maximum Multiplicity: Electrons fill degenerate orbitals one by one before pairing
  • Exceptions in electron configurations for stability: Chromium and Copper configurations
  • Factors contributing to stability: Exchange energy and symmetric distribution of electrons
  • Magnetic properties determined by unpaired electrons: Diamagnetic vs. paramagnetic substances
  • Calculation of magnetic moment using the formula: N(N+2)
  • Importance of electronic configuration in determining magnetic properties
  • Homework assignment: Calculate magnetic moment based on number of unpaired electrons
  • Emphasis on efficient use of study time for maximum learning and revision
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