Atomic theory, wave, and energy locaion

Democritus

Proposed that matter is made of tiny, indivisible particles called atoms

John Dalton

Developed the first modern atomic theory stating atoms of the same element are identical and combine in whole-number ratios

Dalton’s Atomic Theory

States that all matter is made of atoms, atoms are not created or destroyed, and chemical reactions rearrange atoms

J.J. Thomson

Discovered the electron using cathode ray tubes

Plum Pudding Model

Model where electrons are embedded in a positively charged sphere

Ernest Rutherford

Discovered the nucleus through the gold foil experiment

Gold Foil Experiment

Showed that atoms are mostly empty space with a small, dense, positive nucleus

Niels Bohr

Proposed that electrons move in fixed energy levels around the nucleus

Bohr Model

Atomic model where electrons occupy specific energy levels

Quantum Mechanical Model

Modern atomic model that describes electrons as probability clouds

Electron Cloud

Region around the nucleus where electrons are most likely to be found

Proton

Positively charged particle located in the nucleus

Neutron

Neutral particle located in the nucleus

Electron

Negatively charged particle found in the electron cloud

Charge of a Proton

+1

Charge of a Neutron

0

Charge of an Electron

−1

Atomic Number

Number of protons in an atom

Mass Number

Total number of protons and neutrons

How to Find Neutrons

Mass number minus atomic number

Isotope

Atoms of the same element with different numbers of neutrons

Why Isotopes Have Different Masses

Because they have different numbers of neutrons

Electromagnetic Radiation

Energy that travels through space as waves

Wavelength (λ)

Distance between two identical points on a wave

Frequency (f or ν)

Number of wave cycles that pass a point per second

Hertz (Hz)

Unit used to measure frequency

Speed of Light (c)

3.0 × 10⁸ meters per second

Wave Equation

c = λf

How Wavelength and Frequency Are Related

They are inversely related

Long Wavelength Means

Low frequency and low energy

Short Wavelength Means

High frequency and high energy

Electromagnetic Spectrum

All types of electromagnetic radiation arranged by wavelength

Order of EM Spectrum (Low to High Energy)

Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma

Visible Light Spectrum

Range of light humans can see

Red Light

Has the longest wavelength and lowest energy in visible light

Violet Light

Has the shortest wavelength and highest energy in visible light

Energy of Light

Depends on frequency

Planck’s Constant (h)

6.626 × 10⁻³⁴ joule·seconds

Planck’s Equation

E = hf

Photon

A packet of light energy

Higher Frequency Means

Higher energy

Lower Frequency Means

Lower energy

Photoelectric Effect

Electrons are emitted from a metal when hit by high-energy light

What Increases Light Energy

Increasing frequency, not brightness

Electron Energy Levels

Fixed amounts of energy electrons can have

Electron Absorbs Energy When

It moves to a higher energy level

Electron Emits Energy When

It moves to a lower energy level