Anything in black letters = write it in your notes (‘knowts’) Chapter 5 Electrons in Atoms Anything in black letters = write it in your notes (‘knowts’)

Rutherford’s Planetary Model of the Atom 5.1 – Revising the Atomic Model Rutherford’s Planetary Model of the Atom Electrons moving around a tiny nucleus

Problems with Rutherford’s Model Did not explain the chemical properties of the elements. Did not explain atomic spectra (…later…) e- would spiral into the nucleus, but they don’t

Niels Bohr The Bohr Model ~1913 Electrons are found only in specific locations (or orbits) around the nucleus. These orbits are called energy levels. To move from one energy level to another, an e- must gain or lose a quantum of energy. Niels Bohr

The energy levels in atoms are unequally spaced, like the rungs in this unusual ladder. The higher energy levels are closer together.

The Quantum Mechanical Model The modern description of e- in atoms. Similar to Bohr Model except the exact location of an electron is impossible Electron cloud Electrons are likely to be found in electron ‘clouds’ around the nucleus

Atomic orbital – Most probable place for e- to be. Each orbital can hold 2 e- maximum. The orbitals are named s, p, d & f

S (1 type) p (3 types) d (5 types) There are 7 types of f orbitals Don’t worry about these shapes…

Maximum Electron Capacity Orbital Name Types of Orbital Maximum Electron Capacity s 1 p 3 d 5 f 7 x 2 2 x 2 6 x 2 10 x 2 14 Each orbital can hold 2 e- maximum

Maximum Number of Electrons in Energy Level This chart is on page 132 Summary of Principal Energy Levels and Sublevels Energy Level Number of Sublevels Type of Sublevel Maximum Number of Electrons in Energy Level n = 1 1 n = 2 2 n = 3 3 n = 4 4 1s (1 orbital) 2 8 2s (1 orbital), 2p (3 orbitals) 3s (1 orbital), 3p (3 orbitals), 3d (5 orbitals) 18 4s (1 orbital), 4p (3 orbitals), 4d (5 orbitals), 4f (7 orbitals) 32

5.2 – Electron Arrangement in Atoms Aufbau Principle – e- occupy the orbitals of lowest energy first. Pauli Exclusion Principle – Hund’s Rule – we will not cover

Aufbau Diagram (p. 135) E- fill the lowest energy orbitals first Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p E- fill the lowest energy orbitals first Notice the 4s fills before the 3d

Maximum Number of e- Due to Orbitals Another Aufbau Diagram (write this one down!) Orbital Maximum Number of e- Due to Orbitals s 2 p 6 d 10 f 14 Aufbauprinzip, (german) "building-up principle”

1s 2s 2p 2 2 3 7 Electron Configuration – shows how e- are arranged in an atom Example: Nitrogen How many e-? Which orbitals fill first and how many e- can go into each orbital? Write the electron configuration for N 7 See aufbau diagram # of e- in orbitals 1s 2s 2p 2 2 3

Your turn… Write the electron configuration for a) boron b) silicon c) sulfur

Can you see how the periodic table can be used as an Aufbau Diagram?

The Electromagnetic Spectrum (p. 139) 5.3 – Atomic Emission Spectra and the Quantum Mechanical Model The Electromagnetic Spectrum (p. 139) Low energy ( = 700 nm) High energy ( = 380 nm) Frequency  (s-1) 3 x 106 3 x 1012 3 x 1022 102 10-8 10-14

A prism separates light into the colors it contains A prism separates light into the colors it contains. White light produces a rainbow of colors. Screen Prism Slit Light bulb

Light from a helium lamp produces discrete lines. Screen Slit Prism Helium lamp

The lines that result are unique for each element and are called its atomic emission spectrum.

Bohr’s Model explained the emission spectra When an atom absorbs energy an electron jumps to a higher energy level (excited state). The electron returns to the lower energy level, emitting a photon with a definite energy. The photon’s energy shows up as a line in the emission spectrum.

Chapter 5 Quick Quiz Explain the main difference between the Bohr Model and the Quantum Model of the atom. How many electrons can be an atomic orbital? How many types of s, p, d, and f orbitals are there? s = ______, p = _______, d = ______, f = ______ What is the maximum e- capacity of the s orbitals ____, p orbitals ____, d orbitals ____, f orbitals ____

Write the electron configuration for the following elements. Helium Strontium Aluminum Chlorine Silver Arsenic

Chapter 5 Things to Know… Rutherford  Bohr  Quantum Mechanical Models, Energy Levels, Atomic Orbitals (s, p, d, f) , Aufbau Principle & Diagram, Electron Configurations, Explanation of Atomic Emission Spectra