JEE 2024: Structure of Atom Class 11 | One Shot | 1 Month 11th Done | JEE Chemistry #jeepreparation

Vedantu JEE English・2 minutes read

The text covers the structure of the atom, from subatomic particles to atomic models, quantum mechanics, wave equations, and charge calculations, essential for understanding board and JEE exams. Key topics include cathode ray tube experiments, Millikan's oil drop experiment, charge-to-mass ratios, atomic spectra, isotopes, isotones, and Schrodinger's equation, culminating in a comprehensive overview of atomic structure and properties.

Insights

The session on the structure of the atom covers crucial topics for board exams, JEE Mains, and JEE Advanced, including subatomic particles, atomic models, and quantum mechanical models.
The discovery of subatomic particles began with the cathode ray tube experiment, showcasing electron behavior in low-pressure air and under high voltage, independent of electrode materials or gas composition.
Millikan's oil drop experiment demonstrated the quantization of electric charge on droplets, concluding that the charge is an integral multiple of the electron's charge.
Rutherford's experiment deduced that most of the atom is empty, with electrons orbiting the nucleus, leading to the quantized energy levels and structure explained by Bohr's atomic model.
The principles of quantum mechanics, including Heisenberg's uncertainty principle, Hund's rule, and Pauli's exclusion principle, govern electron behavior in orbitals with distinct shapes and quantum numbers.

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Recent questions

What is the photoelectric effect?
The photoelectric effect refers to electrons being ejected from a metal surface when exposed to light, with emission dependent on intensity and threshold frequency. Excess energy transfers as kinetic energy to electrons.
How does Bohr's atomic model explain atoms?
Bohr's model quantitatively explains atoms by proposing electrons move in stationary orbits around the nucleus, with energy emitted or absorbed during energy level jumps.
What is Heisenberg's uncertainty principle?
Heisenberg's principle states the impossibility of precisely determining position and momentum simultaneously, crucial in quantum mechanics and understanding subatomic particles.
What are quantum numbers in electron configuration?
Quantum numbers like ML and MS help count electrons and determine their orbitals, with rules like Aufbau, Hund's, and Pauli's guiding electron filling patterns.
What is Schrodinger's wave equation?
Schrodinger's equation describes the 3D wave motion of electrons, involving parameters like mass, energy, and potential energy to determine electron behavior in atoms.

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Summary

00:00

"Atomic Structure Essentials for Exam Success"

The session on the structure of the atom will last about four to five hours, covering topics crucial for board exams, JEE Mains, and JEE Advanced.
Key topics include the discovery of subatomic particles (electrons, protons, neutrons), atomic models (Thomson's, Rutherford's, Bohr's), and quantum mechanical models.
Other important topics encompass the photoelectric effect, dual behavior of electromagnetic radiation, atomic spectra, orbitals, quantum numbers, and electronic configurations.
The session delves into Schrodinger's wave equation, Heisenberg's uncertainty principle, Hund's rule, and Pauli's exclusion principle.
The discovery of subatomic particles began with the cathode ray tube experiment, showcasing the behavior of electrons in low-pressure air and under high voltage.
Cathode rays move from the cathode to the anode in a straight line, exhibiting negative charge behavior in the presence of electric or magnetic fields.
The behavior of cathode rays is independent of electrode materials or gas composition, highlighting the consistency of electron behavior.
In the presence of electric and magnetic fields, cathode rays deflect, showcasing the charge-to-mass ratio, with electrons having a charge of -e.
Millikan's oil drop experiment demonstrated the quantization of electric charge on droplets, concluding that the charge is an integral multiple of the electron's charge.
By manipulating current flow, Millikan observed changes in droplet speed, leading to the conclusion that the electric charge on droplets is quantized.

18:33

Subatomic Particle Properties and Charge Calculations

The formula for electrical charge is Q = n * e, where Q is the charge, n is an integral multiple, and e is the charge of an electron.
The charge on an electron is -1.6 * 10^-19 C, with the present value being 1.602176 * 10^-19 C.
To find the mass of an electron, use the formula m_e = (1.602176 * 10^-19 C) / (1.758820 * 10^11 C/kg), resulting in a mass of 9.1094 * 10^-31 kg.
The discovery of protons involved using a discharge tube with a perforated anode, where cathode rays changed direction upon hitting a fluorescent screen, leading to the term "anode rays."
The mass of positively charged particles depended on the gas nature, and their behavior in magnetic or electric fields was opposite to electrons.
Neutrons were discovered by Chadwick in 1932, using alpha particles from polonium bombarding beryllium to produce neutral particles with mass but no charge.
The properties of subatomic particles include electron, proton, and neutron symbols (E, P, N), absolute and relative charges, mass per kg, and mass per u.
JJ Thomson determined the charge-to-mass ratio of an electron by measuring cathode ray deflection, resulting in 1.76 * 10^8 C/kg.
Calculating the number of electrons in a particle with a charge of 5.5 * 10^-16 C involves dividing the charge by the electron charge, yielding the answer as option A.
Determining the increasing order of charge-to-mass ratios for neutron, proton, alpha particle, and electron reveals the neutron having the lowest ratio, followed by proton, alpha particle, and electron.

39:14

Atomic Models and Isotopes: A Summary

Isotopes are atoms with identical atomic number but different mass number.
Isobars are atoms with the same mass number but different atomic number, with an example being 14C 6 and 14 7n.
Isotones are elements with the same number of neutrons.
Isosters are species with the same number of atoms and electrons.
Isodipers are elements with the same number of A-2Z.
Isoelectronic species are elements with the same number of electrons.
Paramagnetic and diamagnetic species or atoms have unpaired or zero unpaired electrons, respectively.
Thompson's atomic model, also known as the plum pudding model, describes atoms with a positively charged nucleus and electrons orbiting it.
The model does not adhere to Maxwell's theory of electrodynamics, which states that moving electrons should emit energy and eventually fall into the nucleus.
The distance of closest approach refers to the point where an alpha particle, approaching a positively charged nucleus, turns back due to the repulsion, balancing kinetic and potential energy.

01:00:50

Alpha Particle Kinetic Energy and Distance Calculations

Q1 and Q2 can be represented as k2eZe/R or 2eZe/R, with R denoting the distance.
The alpha particle moves with velocity, reaching a distance R, with potential energy kZe^2/R and kinetic energy 0.
The kinetic energy equation is 1/2MV^2 = 2kZe^2/R, or R = 4kZe^2/MV^2.
M represents the mass of the particle, k is 9 x 10^9, Z is the atomic number, and e is 1.6 x 10^-19C.
The distance of closest approach is crucial for J Mains and J Advanced exams.
To achieve a head-on collision with the nucleus, the alpha particle approaches until R = 4kZe^2/MV^2.
Calculating the number of neutrons in 88 strontium 38 is a simple subtraction, yielding 50.
Rutherford's experiment deduced that most of the atom is empty, with a radius of 10^-10m and electrons orbiting the nucleus.
Identifying ISO diaphores involves calculating mass numbers for different elements.
Determining the charge-to-mass ratio involves utilizing the formula RV^2/2kZe^2, with calculations leading to option A as the answer.

01:21:30

Understanding Electromagnetic Radiation and Quantum Theory

Frequency is the number of oscillations per second, analogous to choosing between Oreo and Marie biscuits to understand frequency.
Wavelength is the distance between two consecutive crests or troughs in a wave.
Amplitude is the maximum distance from the rest position or the height of a crest in a wave.
Velocity of electromagnetic radiation is the speed of light, which is 3 x 10^8 meters per second.
Wave number is the inverse of wavelength, and all electromagnetic radiations travel at the same speed in a vacuum.
The formula C = νλ represents the speed of light as the product of frequency and wavelength.
Electromagnetic radiation spans from cosmic rays to radio waves, with energy increasing from left to right and wavelength increasing from bottom to top.
Black body radiation refers to an ideal body that emits and absorbs radiation uniformly, maintaining thermal equilibrium with its surroundings.
Planck's quantum theory introduced the concept of quantized energy levels in atoms and molecules, with energy directly proportional to frequency.
The photoelectric effect, observed by Hertz in 1887, involves electrons being ejected from a metal surface when exposed to light, with results dependent on intensity, threshold frequency, and kinetic energy.

01:42:03

Photoelectric Effect and Bohr's Atomic Model Explained

Excess energy H Nu minus H Nu naught is transferred to the electron as kinetic energy in the photoelectric effect.
The incident light's frequency must be higher than the threshold frequency Nu naught for electron emission.
The kinetic energy of the electron is determined by the difference between the incident light's energy and the threshold frequency.
Formulas include kinetic energy as half MV square equals H Nu minus H Nu naught and HC by Lambda equals HC by Lambda naught plus kinetic energy.
Graphs illustrate relationships like kinetic energy versus frequency, number of ejected electrons versus frequency, and number of ejected electrons versus intensity.
Stopping potential is the minimum potential needed to halt the photoelectric effect, calculated as kinetic energy equals charge times stopping potential.
Kinetic energy of photoelectrons increases linearly with the frequency of the incident light.
The electromagnetic radiation with the maximum wavelength is radio waves.
Calculation of the velocity of photoelectrons with maximum kinetic energy involves formulas like E equals H Nu and half MV square equals H Nu minus work function.
Bohr's atomic model, proposed by Niels Bohr in 1930, quantitatively explained the structure of the hydrogen atom using Planck's concept of energy quantization.

02:02:23

Atomic Orbits: Energy, Momentum, and Velocity

Electrons in an atom can move around the nucleus in orbits, which are stationary states or allowed energy states.
Orbits are arranged concentrically around the nucleus, forming concentric circles.
Electrons revolve around the nucleus due to the centripetal force provided by the electrostatic force of attraction between the positive nucleus and negative electrons.
The centripetal force pulling electrons towards the nucleus is balanced by a centrifugal force, representing the kinetic energy of the electron.
Energy is emitted or absorbed when electrons jump between energy levels, not during their regular orbiting.
The energy difference between two levels is represented by E2 - E1 or ΔE, which is equal to Hν or Hc/λ.
Only orbits where the angular momentum of the electron is a whole number multiple of H/2π are permitted.
The angular momentum of the electron in an atom is quantized, just like energy.
The formula for the radius of the orbit is R = 52.9n^2/Z in picometers, where Z is the atomic number.
The velocity of the electron in an orbit can be calculated using the formula V = 2.18 x 10^6Z/n m/s.

02:21:24

"Bohr Model, Rydberg Equation, Hydrogen Spectrum"

The potential energy (PE) is calculated as -2K, leading to PE = -2Kz^2/R.
The total energy (TE) is derived as KE + PE, resulting in TE = KE - Kz^2/R.
The value of R is determined as n^2H^2/4π^2mkz^2e^2, which is substituted into the TE formula.
Substituting R into the TE formula yields TE = -Kz^2e^4/2R.
The formula for TE is simplified to TE = -13.6Z^2/n^2 electron volts per atom.
The Rydberg's equation is presented as 1.096x10^7Z^2/n^2, crucial for calculations.
The absorption and emission spectra of hydrogen are discussed, showing their complementary nature.
The hydrogen spectrum includes Lyman, Balmer, Paschen, Brackett, and Fund series.
The limitations of Bohr's atomic model are highlighted, including its restriction to single-electron systems.
The derivation of the Redberg constant formula is explained, essential for spectral line calculations.

02:39:02

Quantum Physics Principles and Rules Explained

Energy gap decreases as you move up, with the infrared region showing a reduction in energy gap.
A formula, Delta n (Delta n + 1) / 2, determines the total number of spectral lines during transitions.
Spectral line splitting in a magnetic field is associated with Deep Roy.
De Broglie's equation relates the wavelength of a moving particle to its mass and velocity.
The circumference of the nth orbit is n times the wavelength of electrons.
The relationship between wavelength and kinetic energy is given by Lambda = root over H Square / 2m.
Formulas for Lambda include H / mV, root over H Square / 2mKE, and root over H Square / 2mQV.
Heisenberg's uncertainty principle states the impossibility of precisely determining position and momentum simultaneously.
The principle of Aufbau rule emphasizes filling lower energy levels first before moving to higher ones.
Hunds Rule dictates that electrons fill subshells singly before pairing up, while Pauli's rule prohibits two electrons from having the same four quantum numbers.

02:59:23

Quantum Numbers, Orbitals, and Wave Functions

ML is the magnetic quantum number, ranging from -L to +L.
MS is the spin quantum number, with values of +1/2 or -1/2.
Understanding these quantum numbers helps in counting electrons and determining their orbitals.
The shape of orbitals varies: s orbitals are spherical, p orbitals are dumbbell-shaped, and d orbitals are double dumbbell-shaped.
Schrodinger's equation describes the 3D wave motion of an electron.
The equation involves double partial differentiation and various parameters like mass, energy, and potential energy.
Transitioning to polar coordinates yields different wave function values (eigenvalues) like PSI 1, PSI 2, etc.
The wave function (PSI) represents the amplitude or most probable function of finding an electron.
PSI Square, not PSI, is crucial for determining the probability of finding an electron in an orbital.
Nodes, where the probability of finding an electron is zero, are determined by radial and angular nodes in the wave function.

03:17:13

"Atomic Energy Levels and Orbital Cuts"

L will be equal to 1, resulting in 3 minus 1 minus 1, which equals 1, leading to one cut.
For 4p, the formula is 4 minus 1 minus 1, resulting in two cuts, with one cut at the bottom.
The energy of a 2py orbital is the same as that of 2px and 2pz orbitals, all at the same level.

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