UNIT 2: ATOMIC THEORY AND PERIODICITY

Section 2: Electrons in the Atom

Review (NOT ON NOTES)

Atoms are the basic units of matter

Nucleus (center of atom) made up of protons and neutrons with a cloud of electrons surrounding it

Electrons in an Atom In order to function properly, atoms

must organize electrons so that they don’t collide.

Electrons become organized into different energy levels.

The outermost electrons in an atom are called the valence electrons.

Energy Levels Energy levels are located at set

distances from the center of the atom

Each energy level can contain a specific number of electrons: 1st Energy Level – Closest to the nucleus; Can hold a maximum of 2 electrons

2nd Energy Level and Beyond (3rd, 4th, etc.) – Each can hold a maximum of 8 valence electrons

Ground vs. Excited State The normal place where an electron would be

is called its ground state. If the atom absorbs ENERGY (light, heat, etc.),

electrons can JUMP UP an energy level. This would be its excited state.

Electrons can not stay at this elevated position, so they fall back down to their original place

When they fall back down, they GIVE OFF waves of energy!

Electromagnetic Spectrum Spectrum of energy with

electric and magnetic properties

Is comprised of… AC power Radio waves Microwaves Infrared radiation Visible light Ultraviolet radiation X-rays Gamma rays

The lists above is in order of decreasing wavelength

Smaller Wavelength = HIGHER energy

Wavelength The distance between similar parts of

the curve (crest to crest; trough to trough)

Visible Light Part of the spectrum that we are able to

see Made up of colors: ROYGBIV

Red, orange, yellow, green, blue, indigo, violet Different colors come from different

wavelengths Red has the longest wavelength and violet has

the shortest wavelength

Light and the Structure of the Atom

Each color in the visible light spectrum is a specific wavelength

When electrons emit energy (fall from excited state back to ground state), they emit a color The color depends on the wavelength of

energy being emitted

Atomic Spectrum

Each element behaves in its own unique way when excited by heat/electricity, producing a very specific pattern of lines of color, called an atomic spectrum

NOW…

Take a moment

to summarize!