CHAPTER 5 “ELECTRONS IN ATOMS”

TERMS 1.Wavelength 2.Frequency 3.Amplitude 4.Electromagnetic spectrum 5.Atomic orbital 6.Excited state 7.Ground state 8.Electron configuration 9.Valence electron Take minutes and create a Vocabulary Poster using a Chapter 3 Term

PARTS OF A WAVE Wavelength Amplitude Origin Crest Trough

Wavelength (represented by λ, the Greek letter lambda) is the shortest distance between equivalent points on a continuous wave. Wave

Frequency (represented by ν, the Greek letter nu) is the number of “waves” that pass a given point per second. One hertz (Hz), the SI unit of frequency, equals one wave per second. Wave

In calculations, frequency is expressed with units of “waves per second,” example: ( ) or (s –1 ). C = speed of wave = 3.00 x 10 8 m/s Wave

Calculating Wavelength of an EM Wave What is the wavelength of a microwave having a frequency of 3.44 x 10 9 Hz? 1. Rearrange

Substitute c and the microwave’s frequency, v, into the equation. Calculating Wavelength of an EM Wave Divide the values to determine wavelength, λ, and cancel units as required.

ELECTROMAGNETIC SPECTRUM: EM SPECTRUM Used to describe electromagnetic radiation Includes a wide range of wavelengths and frequencies. Visible light are the colors we see

STOP Do practice problems on white boards. Then, create your own EM Spectra. Make interpretations of how an EM Spectra reads to you.

Question 1 A helium-neon laser emits light with a wavelength of 633 dm. What is the frequency of this light? What is the wavelength of X rays having a frequency of 4.80 x Hz? Question 2

A laser emits light with a wavelength of 5.65x10 2 mm. What is the frequency of this light? Question 3 What is the wavelength of a ray that has a frequency of 8.94 x Hz? Question 4

SECTION 5.2 Quantum Theory and The Atom

Energy states The lowest energy state is called its ground state. When an atom gains energy, it in an excited state.

Quantum Numbers A quantum number, n, is assigned to each orbit. For the first orbit n = 1, the second orbit, n = 2; and so on.

BOHR SAID THAT: Energy related to orbit Electrons cannot exist between orbits Higher energy level : Further away from nucleus Maximum number of electrons in outermost orbital the energy level is stable (unreactive)

BOHR’S MODEL Nucleus Electron Orbit Energy Levels Nucleus Electron Orbit Energy Levels

CHANGING THE ENERGY A hydrogen atom, with only one electron, and in the first energy level. Ground state

Changing the energy Heat, electricity, or light can move the electron up to different energy levels. The electron is now said to be “ excited ”

Changing the energy As the electron falls back to the ground state, it gives the energy back as light

LINE SPECTRUM OF VARIOUS ELEMENTS

STOP Flame Test

The arrangement of electrons in an atom is the electron configuration. Low-energy systems are more stable. Ground-state Electron Configuration

Orbitals on the PT In order of increasing energy, the sequence of orbitals is s, p, d, and f. S – 2 electrons P – 6 elections D – 10 electrons F – 14 electrons

WRITING ELECTRON CONFIGURATION USE YOUR PT 1.Number row. 2.Orbital 3.Electrons = atomic number

PRACTICE How would you write the electron configuration for Sodium? What’s the atomic number?  11, so the superscript numbers should add to 11 1s 2 2s 2 2p 6 3s 1  Do the superscript numbers should add to 11?

GROUND-STATE ELECTRON CONFIGURATION Three rules apply The aufbau principle/rule The Pauli exclusion principle/rule Hund’s rule These all define how an electron is arranged.

AUFBAU PRINCIPLE States: each electron occupies the lowest energy orbital available. Step 1: determine ground-state by learning the sequence of atomic orbital's The aufbau Diagram

THE AUFBAU DIAGRAM Each box represents an atomic orbital. Fig: 5.17 Page 135

ELECTRON CONFIGURATIONS… 2) Pauli Exclusion Principle - at most 2 electrons per orbital - different spins

ELECTRON CONFIGURATIONS 3) Hund’s Rule- When electrons occupy orbitals of equal energy, they don’t pair up until they have to.

ELECTRON CONFIGURATIONS Let’s write the electron configuration diagram for Phosphorus  We need to account for all 15 electrons in phosphorus

The first two electrons go into the 1s orbital Notice the opposite direction of the spins only 13 more to go... Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

The next electrons go into the 2s orbital only 11 more... Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

The next electrons go into the 2p orbital only 5 more... Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

The next electrons go into the 3s orbital only 3 more... Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f

Increasing energy 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 7p 6d 4f 5f The last three electrons go into the 3p orbitals. 3 unpaired electrons

NOBLE GAS NOTATION Travel back to the last noble gas prior to your element. Sodium last pasted Ne therefore we can write its electron configuration like…  [Ne] 3s 1 Reads: go to Neon then to the 3 rd row in the s orbital 1 element in.

VALENCE ELECTRONS Define as the electrons in the atom’s outermost orbitals.  Example: Sulfur has 16 electron total.  Representative elements go by the column number  Transition metals are given

Valance Electrons

ELECTRON-DOT STRUCTURE Include:  element’s symbol = inner- electrons  Surrounded by dots = valence electrons  Check out Table 5.5 as a Reference

ELECTRON-DOT STRUCTURE O Cl

CLASSWORK Create a poster of your element Include… symbol name electron configuration Aufbau diagram electron-dot structure Noble gas configuration if possible