Presentation on theme: " Unit 4 The Arrangement of Electrons Ch. 4. Exam 4 Analysis Averages The Atom+/25(%) Measurement+/15(%) up from % Phases/KMT+/10(82%) down from."— Presentation transcript:
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 1 Particle-Wave Duality 2 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 10 8 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 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.