Completing the Model of the Atom

Chapter 7 Notes

Objectives

• 7.1 Relate emission spectra to the electron configurations of atoms.

• 7.1 Relate energy levels and orbital's within atoms

• 7.2 Distinguish the s,p,d,and f blocks on the periodic table and relate them to an element's electron configuration.

• 7.2 Predict the electron configurations of elements using the periodic table

More Electron Configurations

Hund’s RulePauli Exclusion Principle

Aufbau Principle

Quick Warm up

• Who is the guy we associate with Electrons and energy levels?

• Bohr

Filling in Electrons

• Electrons can only fill into certain shells • These shells have different shapes associated

with the orbital of the electrons• 4 different shells– S orbital: Circular– P orbital: Dumb bell shape (x, y, z axis)– D orbital: Dumb bell shape (and donut)– F orbital: Dumb bell shape (crazier still)

Electron Orbit Shapes

• Electrons fill into different shells– Different types of shells based off of the way the

electrons orbit the nucleus

Why are they shapes?

• Even though the electron is said to be at a certain location (energy level), the electron is orbiting the nucleus and the shape is a probability of where you will find it

• The orbitals drawn correspond to a greater than 90% chance of finding the electron (if you were to take a snap shot)

Filling in Electrons

• Each orbital can only hold 2 electrons• Each subset of orbitals has different amounts

of orbitals– 1 S orbital per energy level (holds 2 electrons)– 3 P orbitals per energy level (holds 6 )– 5 D orbitals per energy level (holds 10 )– 7 F Orbitals per energy level (holds 14 )

Filling in Electrons

• Electrons fill into the closest available orbital to the nucleus– Closest orbital corresponding to the lowest energy

• 1s22s22p63s23p64s23d104p65s24d105p66s2

– 4f145d106p67s25f146d107p6 • Looks a bit confusing… and would be difficult

to memorize… Periodic Table Ally

Filling in Electrons

Another way of looking at it

• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __ Each line represents an orbital for

electrons to fill in and occupy

Pauli Exclusion Principle

• 3p ____ ____ ____• 3s ____• 2p ____ ____ ____• 2s ____• 1s ____

• Pauli Exclusion Principle: No electrons in the same orbital spin the same direction (denoted by Up and Down arrows)

Rules for Filling in Electrons

• 3p ____ ____ ____• 3s ____• 2p ____ ____ ____• 2s ____• 1s ____ Aufbau Principle: Electrons

fill in the lowest energy levelsavailable (Build up)

Hund’s Rule

• 3p ____ ____ ____• 3s ____• 2p ____ ____ ____• 2s ____• 1s ____ Hund’s Rule: If all

orbitals aren’t filled, first fill them (same spin as first) before pairing the electrons up (want their own space (Attila the Hun)

Writing Out Electron Configs

• Long Hand– Cl (Chlorine) • 1s22s22p63s23p5

– Ca (Calcium)• 1s22s22p63s23p64s2

– Oxygen (O)?– Zinc (Zn)?– Krypton (Kr)?

Review

• How many electrons can each orbital have?• What is the Pauli Exclusion principle?• What is Hund’s rule?• What is the aufbau principle?• What is the shape of a “p” orbital?

Practice: Fill in electrons for Ni

• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Practice: Fill in electrons for Al

• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Practice

• Identify the element by its electron configuration– A) 1s22s22p63s2

– B) 1s22s22p63s23p64s2

– C) 1s22s22p63s23p64s23d104p5

– D) 1s22s22p63s23p64s23d104p65s24d105p66s2

• 4f145d9

Are some electrons more important than others?

• When atoms interact, what is really interacting are the electrons (the electron magnetic field)

• As new electrons are added, the electrons closer to the nucleus are no longer interacting with other atoms

• The outer most electrons are called the• Valence Electrons

Valence Electrons

• Only electrons in the S and P orbitals interact with other atoms and account for the molecules chemical reactivity (for the most part)

• And not all the S and P electrons, just the S and P electrons in the Highest energy level

Valence Electrons

• Example: Sulfur, has an electron configuration of 1s22s22p63s23p4

• The 1s, 2s, and 2p electrons are closer the nucleus and don’t interact 1s22s22p63s23p4

• The highest energy level reached is the 3rd energy level 1s22s22p63s23p4

• We count all the electrons in the S and P at the highest energy level: 6 valence e’s 1s22s22p63s23p4