Electrons In Atoms
Electromagnetic Radiation
• Form of energy that exhibits both
wavelike behaviors and particle
behaviors
Electromagnetic Spectrum
• Shows all forms
of electromagnetic
radiation
Quanta
• Electrons gain/lose energy in set
increments only
• Each set amount of energy is called a
quantum
• Lost energy is released as
electromagnetic radiation, with more
energy = higher frequency
Photoelectric Effect
• Emission of electrons from metal’s
surface when light of specific frequency
shines on surface
light
eMETAL
Wrap-Up #1
• If electrons will only be emitted by light
of high energy, which of the following is
more likely to release electrons?
– Blue light with low intensity (dim)
– Red light with high intensity (bright)
– Radio waves with high intensity
Bohr Model – Electron States
• Ground State
– Lowest energy state of an electron
– Where the electron is “naturally”
• Excited State
– State when an electron gains energy
– Only exists while energy is being absorbed by
the atom
• Glow in the dark materials – the electrons absorb
energy from light and re-release it as light when its
surroundings are dark
Bohr Model
E1 = lowest energy level
E1
E3 > E2 > E1
E2
E3
Ground State to Excited State
4
Energy of atom
1. in ground state, no
energy radiated
2. in excited state,
electrons jump to
higher energy level
(because they’ve
absorbed energy from
an external source)
3. electrons go from high
E level to low E level
4. photon emitted
6
5
4
3
3
2
2
1
1
Atomic Orbitals
• Volume surrounding the nucleus in
which an electron is 90% likely to be
found
Principle Quantum Number (n)
• Indicates the energy level an electron is
on
– Use periodic table to tell
– The period number corresponds to the
principle quantum number (n = 1,2,3…)
Energy Orbitals
• Shape of orbital that tells the path of the
electrons
– 4 orbitals: s, p, d, f
– The letter tells you the shape of the
orbital
s orbital
• Shape: electrons travel in a sphere
s orbital
3s
1s
2s
The greater the energy level, the bigger the orbital
p orbital
• Shape: dumbbell or figure 8 shaped
d orbital
• Shape – double dumbbells or a dumbell
with a ring around it
Electron Configuration
• Description of the arrangement of
electrons in an atom
• Allows us to visualize where the
electrons in an atom can be found
Rules Governing Electron Configurations
1) Aufbau Principle – electrons occupy lowest
energy orbital available
- fill up level 1 first, then level 2, etc.
2) Pauli Exclusion Principle – there is a max
number of electrons that occupy a single
orbital (2) and they must have opposite spin
Rules Governing Electron Configurations
3) Hund’s Rule – if orbitals have equal
energy, one e- will go in each orbital
before doubling up
1
2
3
4
5
6
Rules Governing Electron Configurations
3b) Hund’s Rule – all electrons in singly
occupied orbitals must have the same
spin
Yes
Yes
Yes
NO
NO
NO
Blocks On Periodic Table
s
s
p
d
f
Divisions of Orbitals
• s orbital – 1 sublevel (2 e- max)
• p orbital – 3 sublevels (6 e- max)
• d orbital – 5 sublevels (10 e- max)
• f orbital – 7 sublevels (14 e- max)
Orbital Diagram
• Nitrogen
• How many electrons? 7
1s
2s
2p
Orbital Diagram
• Silicon
• How many electrons? 14
1s
2s
2p
3s
3p
Wrap-Up #2: Orbital Diagram
• Copper
• How many electrons? 29
1s
2s
4s
2p
3d
3s
3p
Electron Configuration Notation
• Oxygen (8 e-)
2
2
1s 2s 2p
4
• Sulfur (16 e-)
2
2
6
2
1s 2s 2p 3s 3p
4
• Vanadium (23 e-)
2
2
6
2
6
2
1s 2s 2p 3s 3p 4s 3d
3
Noble Gas Notation
• Rule: start from previous noble gas,
then write the configuration
• Oxygen [He] 2s 2 2p 4
2
4
[Ne]
• Sulfur
3s 3p
2
3
[Ar]
4s 3d
• Vanadium
Valence Electrons
• Electrons in outer most energy level
- located in highest s & p orbitals
N:
2 2
3
5 valence e
1s 2s 2p
Mg:
2
2
6
1s 2s 2p 3s
2
2 valence e-
Se: 1s2 2s2 2p 6 3s2 3p6 4s 2 3d10 4p 4
6 valence e-
Electron Dot Structure
• Shows valence electrons in a diagram
• Nitrogen (5 v.e.)
N
• Magnesium (2 v.e.)
Mg
• Selenium (6 v.e.)
Se