1. Electrons in Atoms
Section 2.2

2. Electron Motion and Energy
e- and p+ are oppositely charged
So.. Why aren’t electrons pulled into the nucleus?
Niels Bohr
e- have enough energy to keep in motion around the nucleus
ex: Like satellites orbiting a planet-
Called the Bohr Model
But e- behave a little differently

3. Waves Electrons behave like waves, and waves transfer energy
Water waves, sound waves
Movement of e- is electromagnetic radiation
All types of electromagnetic radiations are shown in the electromagnetic spectrum

5. Characteristics of Waves
Wavelength: the shortest distance between equivalent points on a continuous wave
Represented by lambda (λ)
Frequency: number of waves that pass a given point per second
Represented by nu (v)
Measured in hertz (Hz), meaning 1/s
Amplitude: waves height from the origin to the crest (high point) or trough (low point)

6. Wave Equations Speed of light = wavelength x frequency C = λ v
C= 3 x 10 ^8 m/s
Units:
Λ = m
V = Hz (1/s)

7. Electromagnetic Spectrum
A range of all the forms of electromagnetic radiation, separated by frequencies and wavelengths.
Includes radio waves (longest wavelength, lowest frequency), microwaves, infrared, visible light, ultraviolet, X ray, and gamma rays (shortest wavelength, highest frequency)

8. Electrons and Light Electrons and light are related by energy
When atoms are exposed to energy they get excited – their electrons move
This movement results in a release of light energy
The spectrum of light released is called the emission spectrum

9. Energy Levels
When atoms were exposed to an energy source it was found that electrons only absorbed/released certain amounts (frequencies) of energy
This was evidence that energy levels
Regions of space in which electrons can move around the nucleus- existed

10. Electron Cloud Model
Energy levels are not neat, planet- like orbits around the nucleus
They are spherical regions of space around the nucleus where electrons are most likely to be found
Current model of the atom; electron cloud model

11. Arrangements of Atoms
Each energy level can hold a limited number of e-
1st holds 2, 2nd holds 8, 3rd holds 18 and every level after holds 32
The e- in the outermost energy levels are called valence electrons
These are the electrons that interact when atoms come into contact

14. Lewis Dot Structure
We represent valence electrons with Lewis dot diagram
Valence electrons are written as dots around the symbol of an element
Example: