Unit 1 – Atomic Structure Lesson 1: The Electromagnetic Spectrum

Wavelength & Frequency Wavelength – Measured in nm  distance between 2 peaks

Frequency Measured in Hz  # of wavelengths passing a given point in a second

Electromagnetic Spectrum As wavelength decreases, frequency increases

Types of Radiation Gamma Rays – Highest frequency – Sources: nuclear reactions, outer space – Have enough penetrating ability to pass through 3 meters (9 feet!) of concrete – In large amounts can cause radiation poisoning – When controlled, can be used to help cure some cancers

X-Rays – Extensively used in the medical field – Uncontrolled exposure to x-rays, can lead to mutations or cell damage – Used by geologists & chemists for characterizing the structure & properties of crystalline materials Types of Radiation

UV – Some exposure promotes Vitamin D production and tanning – Too much can lead to sunburn, retina damage and cancer Types of Radiation

More UV uses – Kills micro-organisms in water and food – Hardens casts – Insects & birds use UV for navigation

Infrared (IR) – Molecules existing above absolute zero (-273 Celsius) all emit IR, recorded as heat – ½ of the Sun’s energy is emitted in the IR region – Tungsten light bulbs are inefficient. They produce more IR than actual visible light Types of Radiation

Infrared Cont’d

Types of Radiation Microwaves – Highest frequency – Emitted by Earth, buildings, cars, planes – Low level radiation in space

Radio waves Types of Radiation

Visible light (radiation our eyes see) – Ranges from 780 nanometers (deep red) to 400 nanometers (violet) – ROYGBIV – Also called a “continuous spectrum

Visible light cont’d

Electrons travel in specific orbits Emit light when they give off the energy they acquired & fall back to their original orbit

Spectroscopy Emission – Study of the line spectra given off by electrons returning to their original energy level Absorption – Study of the dark lines of a spectra which represents the energy that was absorbed by a sample

The Glowing Pickle! _ks _ks

Historical Development of The Atomic Model John Dalton ( ) – English school teacher, interested in chemistry, physics and meteorology – Developed atomic theory – Published the first list of atomic weights – Died in 1844 after suffering from repeated strokes for over 7 years, although he continued to contribute effectively to science

Dalton’s Atomic Theory 1.All elements are composed of tiny, indivisible particles called atoms 2.Atoms of the same element are identical and those of different elements are different 3.Atoms of different elements can physically mix together or chemically combine in simple whole number ratios to form compounds

4. While chemical reactions occur when atoms are separated, joined, or rearranged, atoms of one element are never changed into atoms of another element as a result of a chemical reaction

JJ Thomson ( ) Plum pudding model

Ernest Rutherford ( ) “gold foil experiment”

Neils Bohr ( ) Proposed electrons are arranged in orbits

-Electrons cannot exist between energy levels -To move up an energy level an electron must gain enough electricity -When it loses this acquired energy, it moves back down to its original energy level

Increasing energy Energy Levels

Louis de Broglie ( ) Wave particle theory Related circumference of orbit to whole number wavelengths of an electron travelling around the nucleus

Erwin Schrodinger ( Defined the probability of finding an electron around the nucleus