Atomic Theory Lecture 1

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Questions and Answers

What are the main elements that the Greek model proposed the universe is composed of?

Electrons and protons

Matter and energy

Matter and space

Atoms and void (correct)

What is one key concept of Dalton's atomic model?

Atoms can be created or destroyed in chemical reactions.

All atoms of an element differ in mass.

Atoms are made of smaller particles.

Compounds are formed by combinations of atoms. (correct)

Which scientist is credited with the discovery of the electron?

John Dalton

Ernest Rutherford

Joseph John Thomson (correct)

Niels Bohr

In Rutherford's model of the atom, what component is considered to contain most of the atomic mass?

Nucleus Signup and view all the answers

According to Bohr's model, how do electrons move around the nucleus?

In orbits of set size and energy Signup and view all the answers

Which atomic model proposed that atoms are uniform spheres of positively charged matter?

Thomson’s model Signup and view all the answers

What was the first model to suggest that atoms are indivisible?

Dalton’s model Signup and view all the answers

What characterizes the modern atomic model compared to earlier models?

Incorporation of quantum mechanics Signup and view all the answers

What is the relationship between wavelength and frequency in electromagnetic radiation?

Wavelength increases as frequency decreases. Signup and view all the answers

What is the value of Planck's constant used in energy calculations?

6.626 x 10^-34 J·s Signup and view all the answers

Which statement is true regarding the energy of radiation?

Energy is directly proportional to frequency. Signup and view all the answers

What is the frequency of light with a wavelength of $700 imes 10^{-9}$ meters?

$4.29 imes 10^{14} s^{-1}$ Signup and view all the answers

In terms of energy, how does light with a longer wavelength compare to light with a shorter wavelength?

Longer wavelength light has lower energy. Signup and view all the answers

Which phenomenon demonstrates the particle nature of light as described in the photoelectric effect?

No electrons are ejected until light reaches a minimum energy threshold. Signup and view all the answers

What effect does an increase in frequency have on the energy of electromagnetic radiation?

Energy increases directly with frequency. Signup and view all the answers

What characterizes electromagnetic radiation with short wavelengths?

High energy and high frequency. Signup and view all the answers

Which statement correctly describes the relationship between an electron's orbit size and its energy?

The largest orbits have the highest energy. Signup and view all the answers

What is a key aspect of Niels Bohr's model of the atom regarding electron transitions?

Radiation is emitted or absorbed during electron transitions. Signup and view all the answers

According to Heisenberg's Uncertainty Principle, what is true about orbitals?

Orbitals are areas where electrons can be found with some probability. Signup and view all the answers

How does the wavelength of a moving body relate to its momentum according to de Broglie's theory?

Wavelength is inversely proportional to momentum. Signup and view all the answers

Which of the following describes when electromagnetic radiation has a long wavelength?

It has low energy and low frequency. Signup and view all the answers

Which formula relates the speed of light, wavelength, and frequency of electromagnetic waves?

$ u = rac{c}{ ext{wavelength}}$ Signup and view all the answers

What characterizes the mechanics used to describe the motion of large bodies compared to tiny particles?

Large bodies are better described by classical mechanics. Signup and view all the answers

What is the significance of Planck’s constant in relation to electromagnetic radiation?

It relates the energy of a photon to its frequency. Signup and view all the answers

How does the size of an electron's orbit relate to its energy levels?

The smallest orbit has the lowest energy, while larger orbits correspond to higher energy levels. Signup and view all the answers

Explain the significance of orbitals in quantum mechanics.

Orbitals are regions where electrons are likely to be found, derived from solutions to Schrödinger's equation. Signup and view all the answers

What does Heisenberg's Uncertainty Principle state about electron position and momentum?

It states that one cannot simultaneously determine the exact position and momentum of an electron. Signup and view all the answers

Describe how de Broglie's theory relates wavelength and momentum.

De Broglie's theory states that the wavelength of a moving body is inversely proportional to its momentum. Signup and view all the answers

How is momentum calculated in classical mechanics compared to quantum mechanics?

In classical mechanics, momentum is calculated as mass times velocity; in quantum mechanics, it also integrates wave properties. Signup and view all the answers

What is the relationship between frequency and wavelength in electromagnetic radiation?

Frequency is inversely proportional to wavelength; as wavelength increases, frequency decreases and vice versa. Signup and view all the answers

What did Albert Einstein contribute to the understanding of electromagnetic radiation?

Einstein's work, particularly on the photoelectric effect, provided evidence for the particle nature of light. Signup and view all the answers

How does electromagnetic radiation behave differently with respect to wavelength and energy?

Electromagnetic radiation with shorter wavelengths has higher energy compared to radiation with longer wavelengths. Signup and view all the answers

What is the formula used to determine the frequency of radiation?

The formula is $ν = \frac{c}{\lambda}$, where $c$ is the speed of light and $\lambda$ is the wavelength. Signup and view all the answers

How does the energy of radiation relate to its frequency?

The energy of radiation is directly proportional to its frequency, given by the equation $E = hν$. Signup and view all the answers

What does the photoelectric effect demonstrate about the nature of light?

The photoelectric effect demonstrates that light exhibits particle-like behavior, where photons can eject electrons from a material. Signup and view all the answers

In the context of electromagnetic radiation, what is the relationship between wavelength and energy?

Longer wavelengths correspond to lower energies, while shorter wavelengths correspond to higher energies. Signup and view all the answers

Define Planck's constant and its significance in physics.

Planck's constant, $h = 6.626 \times 10^{-34}$ J·s, is significant as it relates energy and frequency of radiation in quantum mechanics. Signup and view all the answers

What happens to the frequency of electromagnetic radiation if the wavelength decreases?

If the wavelength decreases, the frequency increases, indicating a higher energy state. Signup and view all the answers

What is the term used to describe the smallest discrete unit of energy in radiation?

The term is 'quantum,' which refers to the fundamental discrete energy level. Signup and view all the answers

How does the temperature of a black body relate to the intensity of radiation it emits?

The intensity of radiation emitted by a black body increases with temperature, following Planck's law. Signup and view all the answers

How did Democritus contribute to atomic theory?

Democritus proposed that the universe is composed of atoms and the void, emphasizing the indivisibility of atoms. Signup and view all the answers

What did Dalton's atomic theory assert about atoms of a given element?

Dalton's theory stated that all atoms of a given element are identical in mass and properties. Signup and view all the answers

In what pivotal way did Thomson's model change the understanding of atomic structure?

Thomson's model introduced the concept of sub-atomic particles by discovering the electron. Signup and view all the answers

How did Rutherford's model alter previous atomic theories?

Rutherford's model revealed that most of an atom's mass is concentrated in a small, positively charged nucleus. Signup and view all the answers

What was a critical aspect of Bohr's model regarding electron behavior?

Bohr's model posited that electrons move in fixed orbits around the nucleus, each with a specific energy level. Signup and view all the answers

What distinguishes the modern atomic model from earlier atomic models?

The modern atomic model incorporates quantum mechanics, describing electron behavior in terms of probabilities rather than fixed orbits. Signup and view all the answers

What critical discovery did Rutherford make concerning the structure of the atom?

Rutherford discovered the nucleus, which contains most of the atomic mass and is positively charged. Signup and view all the answers

In what way did the Greek model of atomic theory differ from Dalton's model?

The Greek model posited that matter is made of atoms and void, while Dalton's model detailed specific properties and behaviors of atoms. Signup and view all the answers

Study Notes

Pharmaceutical Chemistry - Atomic Theory Lecture 1

Recommended Reading: Use "Chemistry and Chemical Reactivity" by Kotz, Treichel, and Townsend. The 7th and 8th editions are available in the library, as well as an e-book version.
General Chemistry Textbooks: All general chemistry textbooks contain a section on atomic theory.
Atomic Model History:
- Greek Model (400 BC): The universe consists of atoms and void.
- Dalton's Model (1803): Matter is made of indivisible, indestructible atoms. All atoms of an element are identical. Compounds are combinations of different atoms. Chemical reactions are rearrangements of atoms.
- Thomson's Model (1904): Atoms are uniform spheres of positive charge with negatively charged electrons embedded. Discovered the electron.
- Rutherford's Model (1911): Most of the atom's mass is in the positively charged nucleus. Negatively charged electrons orbit the nucleus. Discovered the nucleus.
- Bohr's Model (1913): Electrons rotate around the nucleus in orbits. Energy of an orbit is related to size, and the smallest orbit has the lowest energy. Radiation is absorbed or emitted when an electron moves between orbits.
- Modern Atomic Model (Quantum Mechanics): Bohr's orbits are quantized and called orbitals. Orbitals are regions in space where electrons are likely to be found (Heisenberg's Uncertainty Principle).
Models and their Descriptions: Atomic models have been refined over time, with each model building on the deficiencies of the previous one.
Recent Imaging of Orbitals: Field Emission Electron Microscope images of atomic orbitals (s and p) exist.
Wave-Particle Duality (De Broglie): The wavelength of a moving object is related to its momentum. The momentum equals mass multiplied by velocity. The wavelength inversely varies with the momentum.
Electromagnetic Radiation:
- Waves have frequency (ν, Greek letter "nu").
- Frequency is expressed in cycles per second (Hertz - s^-1).
- Wavelength (λ, Greek letter "lambda").
- Radiation velocity (c) =3.00 x 10⁸ m/s
Example Calculation: If red light has a wavelength of 700 nanometers (nm), its frequency is 4.29 x 10¹⁴ s^-1.
Energy of Radiation: The energy of radiation is proportional to frequency (E = hν).
Planck's constant (h): The constant of proportionality for the energy-frequency relationship, which is 6.63 x 10^-34 J•s.
Quantized Energy: The energy emitted by a black body varies in stepwise fashion
Photoelectric Effect:
- Classical theory predicted that increasing light intensity would increase ejected electron energy.
- Experiments showed this was not true.
- Electrons are only ejected when light of a minimum energy (frequency) is used (not intensity)
- Number of electrons ejected depends on light intensity, not frequency.
Photon Concept: Light is comprised of discrete particles called photons.
Energy of 1 mole of Red Light Photons: Example calculation yielding 172 kJ/mol.

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