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

METAL

light e-

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

E1E2

E3

E1 = lowest energy level

E3 > E2 > E1

Ground State to Excited State

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

1

2

3

456

En

erg

y o

f at

om

1

2

3

4

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

1s

2s

3s

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 Configurations1) 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 Configurations3) Hund’s Rule – if orbitals

have equal energy, one e- will go in each orbital before doubling up1 2

4

3

5 6

Rules Governing Electron Configurations3b) Hund’s Rule – all electrons

in singly occupied orbitals must have the same spin

Yes

NO NO NO

Yes Yes

Blocks On Periodic Table

sd

p

f

s

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 2p 3s 3p

4s 3d

Electron Configuration Notation• Oxygen (8 e-)

• Sulfur (16 e-)

• Vanadium (23 e-)

1s 2s 2p2 2 4

1s 2s 2p2 2 6 3s 3p2 4

1s 2s 2p2 2 6 3s 3p 264s2 3d 3

• Rule: start from previous noble gas, then write the configuration

• Oxygen

• Sulfur

• Vanadium

Noble Gas Notation

[He]2s 2p2 4

[Ne]3s 3p2 4

[Ar] 4s 3d2 3

Valence Electrons• Electrons in outer most

energy level- located in highest s & p orbitals

N:

Mg:

Se:

2s 2p2 31s2 5 valence e-

2s 2p2 61s2 3s2 2 valence e-

2s 2p2 61s2 3p 4s6 23s2 3d 4p10 4

6 valence e-

Electron Dot Structure• Shows valence electrons in a

diagram• Nitrogen (5 v.e.)

• Magnesium (2 v.e.)

• Selenium (6 v.e.)

N

Mg

Se