Electrons in Atoms: Electrons in Atoms: Electron ConfigurationElectron Configuration

Chemistry EQs: What is the relationship between

matter and energy?How does the behavior of electrons affect

the chemistry of atoms?

GPSGPS

SC3 Students will use the modern atomic theory to explain the characteristics of atoms.b. Use the orbital configuration of neutral atoms to explain its effect on the atom’s chemical properties.f. Relate light emission and the movement of electrons to element identification.

VocabularyVocabulary

Aufbau PrinciplePauli Exclusion PrincipleHund’s RuleElectron ConfigurationValance ElectronEnergy levels

Lewis StructureGround stateExcited stateOrbitalsQuantum

Excited ElectronsExcited Electrons

Bohr Model of the Atom:Bohr Model of the Atom:

Bohr’s Model: electrons orbit the nucleus; only orbits in certain energies are permitted.

Ground State- lowest E levelExcited State- Higher than ground state.

◦The e- are raised to the next level, then release light when they return to ground state

Must have enough E to raise to next level or won’t happen.

Bohr ModelBohr Model

Bohr Model of the atomBohr Model of the atom

ElectronsElectrons

DeBroglie- Quantum Mechanics- light behaves

as wave & particles Visible objects (baseball) have too

small to see, need very small object to detect

 Heisenburg Uncertainty Principle- Can’t know the position & speed of electron at the same time

Bohr Model Bohr Model Quantum Model Quantum ModelE- do not fall towards nucleus E- reside in electron clouds called orbitals

ElectronsElectrons

Energy levels- region around nucleus where e- likely to be found (electron density is high)

Quantum- amount of energy for e- to jump levels

Continuous- ramp, no units Quantitized- fixed levels, fixed units

Schrodinger- estimates the probability of e- to be in certain area; electrons are like a fuzzy cloud, but more dense= more likely to find e- 90% of the time in a particular location

Orbitals-Wave functions with corresponding densities (shape and energy)

**orbital is NOT the same as Bohr’s orbit

Electron configurationElectron configurationRow=Period=Energy Level => horizontalColumn= Group/ Family=> vertical

◦ Elements in the same family have the same # of valence electrons & share similar chemical properties.

Valence electrons= e- in to last energy level.◦Valence e- correspond w/ group # (does not

include transition elements): Group 1A= 1 valence e- Group 2A= 2 valence e- Group 3A (13) = 3 valence e- Group 4A (14) = 4 valence e- Group 5A (15) = 5 valence e- Group 6A (16) = 6 valence e- Group 7A (17) = 7 valence e- Group 8A (18) = 8 valence e- FULL SET; STABLE

Electron ConfigurationElectron Configuration Tells the arrangement of electrons around

the nucleus of an atom Written in ground state, which is the lowest

energy & most stable arrangement e- arrange from lowest to highest E level

Electron configurationElectron configuration..

Orbital: the 3-D space around the nucleus that describes an electrons probable location.

Energy Level (n): indicate the relative sizes & energies of atomic orbitals. ◦ As n increases, the orbitals become larger, and the e-

spends more time farther from the nucleus. ◦ n = major energy levels; n = 1-7; correspond w/ the 7

rows on the P.T. Sublevel: energy levels contained w/in a energy

level; s, p, d, f

Electron ConfigurationElectron Configuration

What shape are the orbitals?What shape are the orbitals?

s and p Orbitals

Electron ConfigurationElectron Configuration Tells the arrangement of electrons around

the nucleus of an atom

Written in ground state, which is the lowest energy & most stable arrangement

Follows 3 rules:1. Aufbau Principle2. Pauli Exclusion Principle3. Hund’s Rule

Aufbau PrincipleAufbau Principle

Each electron will occupy the lowest available energy level 1st, then higher energy levels.

Pauli Exclusion PrinciplePauli Exclusion Principle A maximum of 2 electrons with opposite

spins can fit in an orbital (No more than 2 e- can

occupy orbitals). e- in the same orbital must have opposite

spin (repulsion); ◦ Show each orbital w/ its own box◦ One is spinning clockwise & the other is counter

clockwise, Show this with one arrow going up & one pointing down.

NOT

Hund’s RuleHund’s RuleSingle electrons with the same spin must

occupy each equal energy level before additional electrons with opposite spins can be added

e- enter orbitals singularly, then pair up◦Example: when filling the p sublevel with 4e-,

each box gets 1 before doubling up one box

NOT

 

Using the PT:•The principal quantum number , n = period.•There are 4 blocks: (s, p, d, f)•Noble gases:full s & p level making them inert (stable).•Alkali Metals- s1

•Alkaline Earth Metals- s2

•Transition Elements- d1-d10

•Inner Transition Elements- f1-f14

Electron ConfigurationElectron Configuration--

Electron Fill SequenceElectron Fill Sequence

Electron ConfigurationElectron Configuration

Electron Sequence ModelElectron Sequence Model

1s

2s

3s

4s

5s

6s

7p

6p

5p

4p

3p

2p

6d

5d

4d

3d

4f

5f

7s

Follow the yellow brick road

Electron ConfigurationElectron Configuration

Examples:F 1s22s22p5

Cl 1s22s22p63s23p5

Al 1s22s22p63s23p1

Br 1s22s22p63s23p64s23d104p5

Orbital Diagrams”Orbital Diagrams”Uses boxes to represent orbitalsUses boxes to represent orbitals

1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 3p 4s 3d 4p

Noble Gas NotationNoble Gas NotationSimplified version of writing e- configurationsNoble gas is placed in brackets [ ]

Noble Gas ShortcutNoble Gas Shortcut

When doing configurations for large numbers of electrons, we can take a short cut using noble gases. (yay!)

Example, lets try Sulfur: (16 electrons)◦The noble gas that comes before Sulfur is: Neon◦Noble gas is placed in brackets [ ]◦Place noble gas in bracket to represent the e-

configuration up to that noble gas.◦Write the rest of the e- config. for that element.◦So we could shortcut by writing: [Ne] 3s2 3p4

Now you try: Manganese and Strontium

Electron Configuration and Orbital Electron Configuration and Orbital NotationNotation

Valence ElectronsValence Electrons

e- in the outer most energy level that determines chemical properties

Lithium = 1s2 2s1

Bromine = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

Aluminum = [Ne] 3s2 3p1

Family NumberVE are the electrons available to form chemical bonds w/ other elements.

Lewis Dot Structure: Electron Lewis Dot Structure: Electron DotDotChemical symbol & valence electrons of atom

Valuable in showing how atoms share electrons in covalent bonds

We can draw Lewis structures for every element using valence electrons

Count the # of valence electron, then arrange then around the symbol for the atom one at a time; up to 8 electrons.

Arrange 1/ side around the symbol, then couple up if more than 4 electrons.

Lewis DotLewis Dot