electrons electrons are found circling the nucleus at extremely fast speeds. + and – attract. the...

Electrons

• Electrons are found circling the nucleus at extremely fast speeds.

• + and – attract. The reason e- are not pulled into the nucleus is because of how fast they are moving. (Kinetic Energy)

Energy

• E- near the nucleus require lower energy

• E- away from the nucleus require higher energy

• E- can jump from one level to another by gaining or losing energy

• Because of this, an e- is most likely to be found in the 1st energy level, closest to the nucleus. (ground state) Aufbau Principle

Energy Level

Max. # of e-

Energy

1 2 Lowest

2 8

3 18 Higher

Electron Energy Levels

• There is a maximum # of e- each level can hold.• The first energy level can hold only 2 e- (H and He)• The second can hold 8 more (Li-Ne)• The third can hold 18, but 8 will fill up first (Na-Ar)

Name electrons 1st 2nd 3rd

Be 4 2 2

Na 11 2 8 1

N

Ar

Valence Electrons

• The e- in the outer most energy level are called

valence electrons.

• The number of valence e- determines how an element bonds.

• We can easily find out how many valence electrons elements in columns 1, 2, and 13-18 have.

• Transition metals (middle of PT) usually have 1 or 2 valence e-. (We cannot predict)

Valence Electrons

1 2 3 4 5 6 7 8

Skip 3-12

Valence cont.

• How many valence electrons do the following elements have?

Ca _______ Si _________

Li ________ Cl _________

P ________ F __________

Ar _______ B __________

Answers

• Ca= 2• Si = 4• Li = 1• Cl = 7• P = 5• F = 7• Ar = 8• B = 3

Sublevels

• Within the energy levels, electrons occupy specific sublevels.

• S- group 1, 2 (2 e-)

• P- group 13-18 (6 e-)

• D- group 3-12 (transition metals) (10 e-)

• F- Lanthanide, Actinide (14 e-)

Energy

• The energy levels don’t fill up perfectly in order.

• E- fill up in order of energy.

• The 4s sublevel requires less energy than the 3d sublevel, so e- fill it first.

• The correct order follows the Periodic Table.

Electron Configuration on the Periodic Table

S BlockP Block

D Block

F Block

What the PT really looks like

6s

4f5d

Electron Configuration

• Write the electron configuration of the following elements:

• Aluminum ___________________

• Chlorine _____________________

Answers

• Aluminum: 1s22s22p63s23p1

• Chlorine: 1s22s22p63s23p5

Noble Gas Configuration

Put the previous noble gas in ( ) and start from there.

•Aluminum– Noble gas [Ne]3s23p1

•Chlorine– Noble gas [Ne] 3s23p5

Electron Configuration-3 rules• Aufbau Principle: e- occupy orbitals of

lowest energy first.• Pauli Exclusion Principle: To occupy the

same orbital e- must have opposite spin• Hund’s Rule: e- don’t double up in an orbital

until they have to.

Carbon:

1s 2s 2p

Find the e- config for Fe

Fe= ____________________________

1s 2s 2p 3s 3p

4s 3d

Electromagnetic spectrum

• The quantum mechanical model grew out of the study of light. Around 1900 light was believed to consist as a wave.

• Electromagnetic spectrum: Radiation over a broad range of wavelengths.

(radio waves longest, gamma rays shortest)

• Visible light was in the middle

c = f x λ

c = speed of light (3.0 x 108 m/sec)

f = frequency of wave (waves per sec) in Hz

λ= wavelength in meters

If the wavelength increases, what should happen to the frequency?

Atomic Emission Spectrum

• When electric current is passed through a gas, the e- are energized.

• When atoms absorb energy, their e- move to higher energy levels.

• These e- lose energy by emitting light when they return to lower energy levels.

• Each element emits a different of spectra of light-like an element fingerprint.

Photoelectric effect

• e- are ejected when light shines on metal…but not every frequency of light works

• E=hv

Einstein

• Einstein determined light can also be described as a quanta of energy that behave as if they were particles. (photon)

• Light behaves as both a wave and a particle.

Heisenberg Uncertainty Principle

• It is impossible to know both the position and velocity of a tiny particle at the same time.

• Once you use lab methods to find position, you alter its motion

• The act of measuring the position of an e- changes its velocity

Electron Dot Diagrams

• Write the element symbol

• Use dots to represent the # of valence e-

• Make a square with up to 2 dots on each side, up to a total of 8.