Unit 4 The Arrangement of ElectronsCh. 4

Exam 4 Analysis

Averages The Atom +/25 (%) Measurement +/15 (%) up from % Phases/KMT +/10 (82%) down from %

**Plan of Action!**

What Do You Think?Electron Placement

Describe the location of electrons in a single lithium (Li) atom.

The Development of a New Atomic Model

Ernest Rutherford Model incomplete did not describe why the electrons where not

pulled to the center of the atom (positively charged nucleus), opposite charges attract.

Early Twentieth Century – New/Revised Atomic Model Absorption and Emission of light by matter Relationship between light and an atom’s electrons

Light behaves like a particle and a wave. (Particle-wave duality) Particle-Wave Duality 1 Particle-Wave Duality 2

Electromagnetic Radiation A form of energy that exhibits wavelike behavior as it travels

through space.

Gamma Rays, X-rays, Ultraviolet, Infrared, Microwaves, Radio waves.

Electromagnetic Spectrum All types of light waves move at a constant speed (3.0 x 108 m/s –

“the speed of light”) through a vacuum (relatively the same for air) Speed = Wavelength x Frequency

c = λν Wavelength – distance between corresponding points on adjacent

waves (meters). Frequency – number of waves that pass a given point in a specific

time.

Photoelectric Effect

Emission of electrons from a metal when light shines on the metal

Electromagnetic radiation (light) strikes the surface of the metal ejecting electrons from the metal and causing an electric current, if the frequency was below a certain minimum.

The Particle Description of Light

Quantum The minimum quantity of energy that can be lost or gained by an

atom.

Photon A particle of electromagnetic radiation having zero mass and

carrying a quantum of energy.

Check for Understanding

What is the difference between the excited and ground state?

List the different types of electromagnetic radiation found in the electromagnetic spectrum.

How are frequency, wavelength, and energy related?

The Hydrogen-Atom Line-Emission Spectrum

Ground State Lowest energy state of an atom

Excited State An atom has higher potential energy than it has in its ground

state When returning to ground state, the atom gives off the energy

it gained in the form of electromagnetic radiation (light) Video

Line-Emission Spectrum When a narrow beam of emitted light is shined through a

prism, it then is separated into four specific color(s) of the visible spectrum.

Bohr Model of the Hydrogen Atom

Niels Bohr Proposed a hydrogen-atom model that linked the atom’s electron

to photon emission The electron can circle the nucleus only in allowed paths called

ORBITS Absorption

Energy must be added to an atom in order to move an electron form a lower energy level to a higher energy level.

Emission When the electron falls to a lower energy level A photon is emitted (light)

The Quantum Model of the Atom

The Heisenberg Uncertainty Principle States that it is impossible to determine simultaneously both the

position and velocity of an electron or any other particle. One of the fundamental principles of our present understanding

of light and matter.

The Quantum Model of the Atom

The Schrodinger Wave Equation Hypothesis that electrons have a dual wave-particle nature Helped lay the foundation for Modern Quantum Theory Describes mathematically the wave properties of electrons and

other very small particles. Gives only the probability of finding electrons at a given place

around the nucleus Electrons do not travel in neat orbits, now in regions called

orbitals 3-D region around the nucleus that indicates the probable location

of an electron Different shapes and sizes

Flame Test Lab

See hand-out.

7 Stations

15 minutes to complete

Emission Spectra

Bulbs (H, He, Ne, Ar, and N)

and Emission Spectra.

“The relationship between electrons and energy is...... The emission spectra is produced by......”

Electron Orbital

-Electrons orbit the nucleus in orbital clouds.

-Electrons with different amounts of energy exist in different energy levels.

The Electron Cloud Model

Electrons in each energy level

• Each energy level can hold a limited number of electrons.

• The lowest energy level is the smallest and the closest to the nucleus.

Electron Orbital Continued

Energy Level # of Electrons

1 2

2 8

3 18

4 32

Draw the Atoms

Lithium Atom:

3 Protons

3 Neutrons

3 Electrons Aluminum Atom:13 Protons13 Neutrons13 Electrons

Valence Electrons

• The electrons in the outermost energy level are called valence electrons.

• See Periodic Table

- Complete in YOUR notes!

Determine the number of protons, neutrons, electrons AND draw the Bohr models of the following atoms:

A. Gallium

B. Krypton

C. Sulfur

D. Titanium

For Next Time…

Complete Part 1 Formative in first 5 minutes of class!

Read pages 111-122!!