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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.