Chem

What do these 6 items all have in common?

Electromagnetic radiation - a form of energy that has wavelike properties - all forms found in the electromagnetic spectrum Examples of electromagnetic radiation: Xrays Microwaves Light waves Radio waves – when you hear static on the radio when you aren’t getting a signal, that is the leftover microwaves from the big bang 15 billion years ago (it is cooling off so now the waves are the energy and wavelength of radio waves)

ELECTROMAGNETIC RADIATION RADIO WAVES MICRO- WAVES INFRARED LIGHT VISIBLE LIGHT UV LIGHT X-RAYS LOWEST ENERGY HIGHEST ENERGY

Listening to music in the car using the radio RADIO WAVES Listening to music in the car using the radio

MICROWAVES Making popcorn

Using the remote control INFRARED LIGHT Using the remote control

The blue color of the sky VISIBLE LIGHT The blue color of the sky

ULTRAVIOLET LIGHT Using a tanning booth

X-RAYS Checking to see if the ankle was broken

WAVELENGTH AND FREQUENCY ARE TWO IMPORTANT PROPERTIES OF WAVES. DIFFERENT FORMS OF EMR TRAVEL IN WAVES. WAVELENGTH AND FREQUENCY ARE TWO IMPORTANT PROPERTIES OF WAVES.

Wave Characteristics Amplitude Wavelength Wavelength 2 sec 0 sec Amplitude Wavelength Wavelength Frequency Amplitude The shortest distance between two equivalent Points (meters) How many waves pass a certain point per sec. (s-1 OR Hz) Wavelength – the shortest distance between two equivalent points on a wave Frequency – how many wave pass a certain point per second Amplitidude –the height of the wave from crest to origin State: Light travels as photons; photons have no mass but have energy The energy a photon has is based on the equation E = hv Energy is directly proportional to the frequency. Frequency has a unit of Hz which is = 1 𝑠 or s-1 or per second. Wavelength is also related to frequency; how many people know the speed of light? Yes, what is it? EA 3 x 108 m/s The speed of light is a constant that is known. Speed of light is based on the speed it travels over time. Wavelength is in meters and frequency is per second, so c=vλ The height of a wave from crest to origin

THE HIGHER THE FREQUENCY, THE SHORTER THE WAVELENGTH FREQUENCY = THE NUMBER OF WAVES THAT PASS BY A FIXED POINT PER SECOND. THE HIGHER THE FREQUENCY, THE SHORTER THE WAVELENGTH

THE HIGHER THE FREQUENCY, THE HIGHER THE ENERGY FREQUENCY = THE NUMBER OF WAVES THAT PASS BY A FIXED POINT PER SECOND. THE HIGHER THE FREQUENCY, THE HIGHER THE ENERGY

THE HIGHER THE ENERGY, THE SHORTER (SMALLER) THE WAVELENGTH

Practice

Electrons and Energy Levels Each electron has a distinct amount of energy that is related to the energy level (shell) it is in Electrons with the lowest energy are found in the shell closest to the nucleus Electrons with the highest energy are found in the shell furthest from the nucleus The greater the distance from the nucleus, the greater the energy of the electron

Each energy level has a maximum number of electrons that it can hold The smallest energy level (the one closest to the nucleus, the first) can hold 2 electrons. The second energy level, can accommodate 8 electrons. The third energy level, can accommodate 18 electrons. The 4th energy level can accommodate 32 electrons N e 1 2 2 8 3 18 4 32

HOW DOES A NEON SIGN WORK? BECAUSE OF ELECTRONS

Ground vs. Excited State Ground state=when the electrons occupy the lowest energy levels possible Excited state= on or more electrons gain energy and move to a higher energy level or shell (leaving the lower energy levels to be not completely full)

Ground and Excited State When an electron gains energy, it jumps to a higher energy level or shell This is a very unstable condition We call this condition the excited state Very rapidly, an electron in the excited state will lose energy and move back to a lower energy level or shell When excited electrons fall from an excited state to a lower energy level, they release energy in the form of light

Ground  Excited State Electron gains energy from heat, light, electricity Electron “jumped” to a higher energy level (shell)

Excited  Ground State Electron releases energy in the form of light Electron “falls” back and returns to ground state (normal position)

Bright Line Spectrum Electrons falling from an excited state down to the ground state give off visible light Different elements produce different colors of light or spectra These spectra are unique for each element (just like a human fingerprint is unique to each person)

Demo