The Quantum Model of the Atom What atoms really look like. (We Think?)

The Bohr Atom The Bohr model of the atom has electrons orbiting the nucleus in orbit that we call energy levels. Electrons are particles like little planets going around the nucleus. Electrons can move between energy levels absorbing or giving off light. Called atomic spectra.

Emission spectra “atomic finger prints”

A problem with Bohr’s atom. Electrons traveling in an orbit should give off light continuously … they don’t. Why? Bohr didn’t know, his model just worked.

What are electrons? – 1924: De Broglie said that electrons were waves containing specific amounts of energy (like Bohr’s energy levels) – But no one said that they weren’t still a particle

Heisenberg Uncertainty Principle We can only observe electrons by interaction with photons. Interactions with photons cause electrons to move. Problem? 1927 – Heisenberg says: we can’t know where an electron is AND where it is going at the same time.

Quantum Theory 1926: Erwin Schrödinger calculated electrons as waves and found only specific energies worked (once again, just like Bohr)

Solve!

Orbital A three dimensional space around the nucleus where an electron is likely to be found. Described by Schrodinger equation as a probability of finding the electron.

Quantum Numbers Tell us where electrons are LIKELY TO BE based on energy states of electrons. There are 4 numbers to describe each electron. The 1) energy level, 2) the sub level, 3) the orbital and 4) the spin. Pauli exclusion principle: no two electrons in the same atom can have the same four quantum numbers

1) Energy Level “principle quantum number” Indicates main energy level just like Bohr’s model There are 7 energy Levels As n increases, so does the energy and distance from nucleus

2) The Sub Level Describes the SHAPE There are 4 shapes The specific orbital the electron is in. s has 1, p has 3, d has 5, f has 7 3) The Orbital

s orbitals are spherical

p orbitals are dumbell shaped

d orbitals are complex

f orbitals are really complex

4) The Spin For each orbital there are two spins: up and down. Thus, each orbital contains two electrons

s = electron Up spin Down spin

p = electron down up down up down

d = electron up down

f 14 electrons total!

How are orbital shapes related to the energy levels spdf n = 11s n = 22s2p n = 33s3p3d n = 44s4p4d4f n = 55s5p5d5f5g n = 66s6p6d6f6g6h n = 77s7p7d7f7g7h n = 88s8p8d8f8g8h

As energy level goes up, orbitals get bigger! 2s is larger than 1s 3p is larger than 2p 3s is larger 2s etc.

Sub Level Number of Orbitals in the Sub Level Number of Electrons Needed to Fill Sub Level Total Number of Orbitals in the Energy Level n 2 Total Number of Electrons in Energy Level 2n 2 1s1212 2s12 2p3648 3s12 3p36 3d s12 4p36 4d510 4f

The Periodic Table Remember: # of electrons = atomic number Where does each electron go? Electron Configuration: Arrangement of electrons in an atom.

Rules! Aufbau principle: an electron occupies the lowest-energy orbital that it can. Hund’s Rule: orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron.

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p Lowest EHighest E

Six boys move into a new house.

Hydrogen 1s = electron

Helium 1s

Lithium 1s 2s

Beryllium 1s 2s

Boron 2s2s 2p2p 1s

Carbon 1s 2s2s 2p2p

Nitrogen 1s 2s2s 2p2p

Oxygen 1s 2s2s 2p2p

Fluorine 1s 2s2s 2p2p

Neon 1s 2s2s 2p2p

Orbital Notation 1s 2s2p

Hydrogen 1s 1 2s2p Electron Configuration 1s

Helium 1s 2s2p 1s 2 Electron Configuration

Lithium 1s 2s2p 1s 2 2s 1 Electron Configuration

Beryllium 1s 2s2p 1s 2 2s 2 Electron Configuration

Boron 1s 2s2p 1s 2 2s 2 2p 1 Electron Configuration

Carbon 1s 2s2p 1s 2 2s 2 2p 2 Electron Configuration

Nitrogen 1s 2s2p 1s 2 2s 2 2p 3 Electron Configuration

Oxygen 1s 2s2p 1s 2 2s 2 2p 4 Electron Configuration

Fluorine 1s 2s2p 1s 2 2s 2 2p 5 Electron Configuration

Neon 1s 2s2p 1s 2 2s 2 2p 6 Electron Configuration

Noble Gas Configuration To help you be lazy! Write noble gas in [ ] that precedes the element. Then only write electrons that exist thereafter. The electron configuration for Helium is NOT [He]!

1 H 1s 1 2 He 1s 2 3 Li [He]2s 1 4 Be [He]2s 2 5 B [He] 2s 2 2p 1 6 C [He] 2s 2 2p 2 7 N [He] 2s 2 2p 3 8 O [He] 2s 2 2p 4 9 F [He] 2s 2 2p 5 10 Ne [He] 2s 2 2p 6 11 Na [Ne] 3s 1 12 Mg [Ne] 3s 2 13 Al [Ne] 3s 2 3p 1 14 Si [Ne] 3s 2 3p 2 15 P [Ne] 3s 2 3p 3 16 S [Ne] 3s 2 3p 4 17 Cl [Ne] 3s 2 3p 5 18 Ar [Ne] 3s 2 3p 6

19 K [Ar] 4s 1 20 Ca [Ar] 4s 2 21 Sc [Ar] 4s 2 3d 1 22 Ti [Ar] 4s 2 3d 2 23 V [Ar] 4s 2 3d 3 24 Cr [Ar] 4s 1 3d 5 25 Mn [Ar] 4s 2 3d 5 26 Fe [Ar] 4s 2 3d 6 27 Co [Ar] 4s 2 3d 7 28 Ni [Ar] 4s 2 3d 8 29 Cu [Ar] 4s 1 3d Zn [Ar] 4s 2 3d Ga [Ar] 4s 2 3d 10 4p 1 32 Ge [Ar] 4s 2 3d 10 4p 2 33 As [Ar] 4s 2 3d 10 4p 3 34 Se [Ar] 4s 2 3d 10 4p 4 35 Br [Ar] 4s 2 3d 10 4p 5 36 Kr [Ar] 4s 2 3d 10 4p 6

Exceptions! Half filled orbital sets are happy! Completely filled orbital sets are happy!