 # Where is the Electron Located?

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Where is the Electron Located?

WHAT IS ENERGY? ABILITY TO DO WORK MEASURED IN JOULES (J)
WORK: TO USE A FORCE TO MOVE AN OBJECT A DISTANCE F X d KINETIC: ENERGY DUE TO MOTION POTENTIAL: ENERGY DUE TO POSITION

WHAT ARE THE DIFFERENT FORMS OF ENERGY?
Law Of Conservation of Energy (also known as the First Law of Thermodynamics): Energy cannot be created or destroyed it merely changes form HEAT (THERMAL) ELECTROMAGNETIC CHEMICAL NUCLEAR MECHANICAL SOUND LIGHT (RADIANT)

THE DUALITY OF LIGHT LIGHT IS A VIBRATION (WAVE) IN ELECTRIC AND MAGNETIC FIELDS THAT CAN TRAVEL ACROSS SPACE AS A PHOTON (PACKET OF ENERGY). IT IS PART OF THE ELECTROMAGNETIC SPECTRUM. LIGHT CAN BE REFLECTED, REFRACTED AND DIFFRACTED

WAVE PROPERTIES WAVELENGTH (λ): DISTANCE BETWEEN TWO IDENTICAL POINTS ON A WAVE (METERS, m) FREQUENCY (ƒ): NUMBER OF WAVES THAT PASS A FIXED POINT IN A SECOND (HERTZ, Hz) SPEED OF LIGHT: c = ƒλ (3.00 X 108 m/s)

Waves

Albert Einstein Suggested that electromagnetic radiation can be viewed as a stream of particles called photons PHOTOELECTRIC EFFECT: Ejection of electrons from the surface of a metal or other material when high energy/frequency light shines on E = h ƒ E = Energy H = Planck’s Constant(6.63 X 1034 J/s) f = Frequency

Albert Einstein Developed the equation E = mc2 Energy has mass
We can calculate the mass of a photon

Arthur Compton Collided X-rays with electrons
Showed that photons do exhibit the mass from Einstein’s equation

Nature of Matter Max Planck – German physicist
Experimented with energy Energy can be lost or gained only in whole-number multiples Energy is “quantized”

Summary Energy is quantized
Electromagnetic radiation exhibits wave-like and particle-like behavior Large pieces of matter mostly exhibit particle-like properties Tiny pieces, like photons, exhibit mostly wave-like Intermediate, like electrons, exhibit both

The Bohr Model Developed a quantum model for hydrogen
Electrons moved in circular orbits around the nucleus Equation that can be used to calculate the change in energy when an electron changes orbits: E = X 10-18J (Z2/n2) n = an integer Z = nuclear charge

BOHR’S ATOMIC THEORY

HOW CAN A LINE SPECTRA IDENTIFYAN ELEMENT?
LINE SPECTRUM: Shows only specific wavelengths of light (EM spectra) What are uses of line Spectra in technology?

The Bohr Model Ground state – lowest possible energy state for an electron Suppose an electron in level n = 6 of an excited hydrogen atom falls back to level n = 1. Calculate the change in energy when this happens. ΔΕ = energy of final state – energy of initial state What is the wavelength of the emitted photon? E = X 10-18J (Z2/n2) E = h ƒ c = ƒλ (c = 3.00 X 108 m/s)

The Quantum Mechanical Model
Bohr’s equation only worked for hydrogen Heisenberg, de Broglie, and Schrodinger developed the theory behind our current model Schrodinger came up with a mathematical equation to describe the location of the electron A specific wave function = an orbital Led to the Heisenberg uncertainty principle and the exact speed of light (c)

The Quantum Model of the Atom
Heisenberg uncertainty principle: It is impossible to determine both the position and velocity of an electron or any other particle

What is the Address of the Electron?
Principle Quantum Number (n): Indicates the energy level occupied by an electron. Angular Momentum (l): Indicates the shape of the orbital (s,p,d,f,g)

Atomic Numbers and Quantum Numbers
Magnetic Quantum Number (m): Indicates the orientation of an orbital around the nucleus. Spin Quantum Number (↓↑): Indicates which way the electron is spinning

Quantum Numbers Symbol What It Means Acceptable Values n
Main energy level 1, 2, 3, 4, etc. l Orbital shape 0, 1, 2,…n-1 ml Space orientation -l…0…+l ms Electron spin +1/2 and -1/2

What are the Rules Governing Electron Configuration?
Aufbau Principle: An electron occupies the lowest energy orbital available Pauli Exclusion Principle: Only two electrons per orbital and they must spin in opposite directions Hund’s Rule: Each orbital of equal energy must have one electron before a second electron is added

Let’s Fill Up The Orbitals!

Summary of Orbitals Principle Quantum # Sublevels Number of Orbitals
Number of Electrons 1 s 2 s, p 3 8 s, p, d 5 18 4 s, p, d, f 7 32

Exceptions to Aufbau