Atomic Structure and Discoveries Quiz

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Questions and Answers

What aspect of atomic structure does the Rutherford model fail to explain?

The size of the nucleus

The electronic configuration of atoms (correct)

The types of ions formed

The presence of neutrons

Why is the Rutherford model compared to a solar system?

Because it depicts a central nucleus surrounded by electrons like planets (correct)

Because it considers both electromagnetic and gravitational forces

Because it represents all atomic particles equally

Because it explains electron orbits accurately

What is a significant drawback of using classical mechanics to describe electron motion?

It cannot account for quantum behavior of electrons (correct)

It accurately describes electron stability

It suggests stationary electrons are more stable

It shows electrons have fixed orbits in a predictable manner

What issue arises from considering electrons as stationary around the nucleus?

There would be a collapse of the atomic structure Signup and view all the answers

How does the Rutherford model relate to ion formation?

It does not address how electrons gain or lose energy Signup and view all the answers

What is a black body characterized by?

It emits and absorbs radiations of all frequencies. Signup and view all the answers

How does the intensity of radiation emitted by a black body vary with wavelength?

It reaches a maximum value at a given wavelength and then decreases. Signup and view all the answers

What is the phenomenon whereby electrons are ejected from certain metals when exposed to light?

Photoelectric effect. Signup and view all the answers

What type of equipment is used in the study of the photoelectric effect?

A vacuum chamber with a detector. Signup and view all the answers

Which of the following factors does not affect the distribution of black body radiation?

The material composition of the black body. Signup and view all the answers

What is the threshold frequency (ν₀) for the metal described in the content?

$7.0 × 10^{14} s^{-1}$ Signup and view all the answers

Using Einstein's equation, which of the following represents the process of an electron emitting radiation?

Kinetic energy = h(ν − ν₀) Signup and view all the answers

What happens to atoms and molecules after they absorb energy from electromagnetic radiation?

They become excited and move to a higher energy state. Signup and view all the answers

What type of spectrum is produced when a substance emits radiation after absorbing energy?

Emission spectrum Signup and view all the answers

What does ν represent in the equation for kinetic energy of an emitted electron?

The frequency of the incident radiation Signup and view all the answers

What is the fundamental unit of electrical charge represented by in the equation q = n e?

e Signup and view all the answers

What determines the charge to mass ratio of positively charged particles discovered in canal rays?

The type of gas in the cathode ray tube Signup and view all the answers

Which of the following statements about positively charged particles in canal rays is true?

They carry a charge that is always a multiple of the fundamental unit. Signup and view all the answers

What type of force is NOT mentioned as acting on the oil droplets in Millikan's apparatus?

Magnetic force Signup and view all the answers

Which statement accurately describes the behavior of positively charged particles compared to electrons?

They experience opposite forces in magnetic fields. Signup and view all the answers

What is the formula for angular momentum of an electron moving in a circular orbit?

$mevr$ Signup and view all the answers

Which of these statements is true regarding the principal quantum numbers of an electron in a hydrogen atom?

They can be any positive integer. Signup and view all the answers

What is the expression for the radius of the nth stationary state in a hydrogen atom according to Bohr's theory?

$rn = n^2 a_0$ Signup and view all the answers

What determines the stationary orbits that an electron can occupy?

The integral multiples of $h/2π$ for angular momentum Signup and view all the answers

How is the frequency of radiation absorbed or emitted during transitions between stationary states calculated?

$f = rac{ΔE}{h}$ Signup and view all the answers

Study Notes

Discovery of Protons and Neutrons

Modified cathode ray tubes enabled the identification of positive charges, termed canal rays.
Millikan's experiments demonstrated that the charge (q) on oil droplets is an integral multiple of the elementary charge (e); q = n*e (where n = 1, 2, 3...).
Canal rays are positively charged gaseous ions, their charge-to-mass ratio varies by gas type.
The smallest positive ion identified is the proton, derived from hydrogen.
Rutherford's model suggests stability is questionable under classical mechanics due to electron movement.

Drawbacks of Rutherford Model

The Rutherford atomic model likens an atom to a miniature solar system, where electrons orbit a dense nucleus.
The model neglects the electronic structure, particularly how electrons are distributed around the nucleus.
Classical mechanics predicts instability since electrostatic attraction would lead to electrons spiraling into the nucleus.

Black Body Radiation

Black body radiators emit radiation based solely on temperature, characterized by a maximum intensity at specific wavelengths.
The intensity of radiation increases with temperature but decreases as wavelength shortens beyond a certain point.

Photoelectric Effect

In 1887, Hertz discovered that exposing specific metals (like potassium, rubidium, cesium) to light emitted electrons, termed the photoelectric effect.
A critical frequency (threshold frequency) is required for electron ejection; below this threshold, no electrons are emitted.
Light of higher frequency can liberate electrons with measurable kinetic energy, governed by the equation: KE = (h*(ν - ν₀)) where ν₀ is the threshold frequency.

Emission and Absorption Spectra

When substances absorb energy, they emit radiation, forming an emission spectrum.
Excited atoms or molecules transition to lower energy states, releasing radiation at characteristic frequencies.

Angular Momentum in Electron Orbits

Angular momentum (L) for an electron in circular motion around a nucleus is quantized and defined as: L = mevr (where v is linear velocity).
Only certain orbits are permissible, associated with integer multiples of h/2π (Planck constant).
The Bohr model sets fixed orbits (n = 1, 2, 3...) corresponding to principal quantum numbers, with the first radius at r₁ = 52.9 pm (a₀).

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Description

Test your knowledge on the discovery of protons and neutrons, along with the limitations of the Rutherford model. This quiz covers key experiments and concepts, such as canal rays and black body radiation. Evaluate your understanding of atomic structure and its implications in classical mechanics.