Chapter 4 Electrons

ELECTRON BEHAVIOR

Who made this model of the atom?

What did Bohr discover? **ENERGY LEVELS!! electrons are around the nucleus in fixed orbits (like the planets around the sun!)

Electrons are always moving!  Electrons are on distinct paths called orbits.  The farther the electron is from the nucleus, the more energy it has.  Electrons can change energy levels and emit a photon of light.  Photon: packet of energy

Electron Movement Vocabulary  Ground State: electrons in the lowest possible energy level  Excited State: electrons absorb energy and move to a higher energy state  Emission : when an electron falls to a lower energy level, a photon is emitted  Absorption : energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level  Quantum: amount of energy needed to move between energy levels

Electron Movement

 When electrons moves from the excited state to the ground state they emit a photon of light  The light emitted by an element is viewed as a bright line emission spectrum  Each band of light represents the energy released by an electron when it moves from higher to lower energy

Light is organized on the: Electromagnetic Spectrum

Because electrons move so much… WE CANNOT KNOW AN ELECTRONS EXACT POSITION OR SPEED AT THE SAME TIME Heisenberg Uncertainty Principle:

Schrodinger  Don’t know the exact position…  Predict where electron will be 90% of the time  Each energy level has a different region of probability

Electron Location

DO NOW  How would you describe your current location? Start off really broad, as in the United States, and describe your location to be more specific.  How would you describe the location of an electron?  Do electrons stay in the same place?

We do not know where the electrons are, but we can describe where they might be

First Location: ENERGY LEVEL n = 1, 2, 3, 4 …

ENERGY LEVEL SUB- LEVEL

Second Location: SUBLEVEL These are the probability regions called: s, p, d, f

SUB- LEVEL ORBITAL

Energy 1s 2s 3s 4s 5s 2p 3p 4p 3d Third Location: ORBITAL s = 1p = 3d = 5 f = 7

How to fill in an Orbital Diagram

Energy Electron Configuration for: Hydrogen Step 1: Electrons are represented as arrows and drawn one at a time. Electrons start at the lowest possible energy. 1s 2s 3s 4s 5s 2p 3p 4p 3d

Energy  Paired electrons Electron Configuration for: Helium Step 2: Electrons have opposite spins. Draw one up and one down. 1s 2s 3s 4s 5s 2p 3p 4p 3d

Energy Electron Configuration for: Oxygen Step 3: Electrons will spread out first before they pair up. Draw electrons in each orbital first then pair them.  Unpaired electron 1s 2s 3s 4s 5s 2p 3p 4p 3d

What is the electron configuration of S? S 16 electrons Energy 1s 2s 3s 4s 5s 2p 3p 4p 3d

What is the electron configuration of Sr? Sr 38 electrons 1s 2s 3s 4s 5s 2p 3p 4p 3d Energy

Outermost subshell being filled with electrons

Why is location important? location influences behavior

Valence Electrons  valence electrons:  electrons in the outermost energy level  can be lost, gained, or shared  electrons that are responsible for reactions  Elements in a group have similar properties because they have the same number of valence electrons

How many valence electrons in each group? Only the main block elements!

All electrons under the highest energy level Inner Core Electrons