LT1: Electron Arrangement (Ch. 5)

How do fireworks work?

Rutherford’s Model of the Atom Contributions Problems Nucleus: Explains where positive protons are and where the majority of the mass of the atom is found Electron Arrangement: electrons are outside the nucleus flying in empty space Doesn’t explain electron arrangement, why electrons aren’t pulled into nucleus, or reactivity/properties of atoms (related to electron arrangement)

EM radiation has Characteristics of Waves Frequency= number of waves passing a point in a given amount of time.

What is the relationship between wavelength and frequency of EM waves What is the relationship between wavelength and frequency of EM waves? How is Energy related?

Electromagnetic Radiation- waves created by electric and magnetic fields moving at right angles to each other.

What does amplitude tell you about the wave?

Why did the wave model of light need a revision? It didn’t explain why only certain colors are emitted from heated objects. It didn’t explain why metals emit electrons when struck by certain types of light.

Planck and Quantum Matter can only gain a CERTAIN AMOUNT OF ENERGY= QUANTUM The colors emitted from an object when heated is directly related to the Quantum.

Is light a wave or a particle?

Why do we see colors from neon signs? What do you think the color depends on?

Explanation--- remember ROYGBIV Atoms are struck by Energy (light, flame, electricity). The electrons are excited out of ground state to excited state where they are unstable. As electrons fall back to ground state they give off the energy they absorbed as LIGHT. The color depends on the quantum absorbed. Higher quantum= BIV Lower quantum= ROY

Atomic emission spectrum= set of frequencies an atom gives off- continuous color is broken down with a spectroscope--fingerprint for an atom

LAB Question: Why does copper emit green and strontium emit red? Use the terms: quantum, ground state, excited state, energy level, frequency, wavelength, and electron.

Quantum Mechanical Model- describes electron arrangement in Energy levels and Orbitals Quantum Mechanical Model answers: How do electrons move around the nucleus of an atom? How does ENERGY determine arrangement? What are ENERGY LEVELS? What are ORBITALS?

Bohr’s Model ENERGY LEVELS: Contributions Visual ENERGY LEVELS: Electrons move in circular patterns around the nucleus like planets around the sun. Closer to the nucleus= lower energy Further from nucleus= higher energy QUANTUM NUMBER: n=1 closest to nucleus Movement from n= 2 to n=1 results in a photon

Problems with Bohr Model Doesn’t explain electron movement within Energy Levels correctly Electrons DO NOT orbit like planets around the sun Only works for Hydrogen

Accepted theory today: Quantum Mechanical Model of the Atom http://www Electrons are treated like waves Electrons have certain ENERGY VALUES which dictate their distance from the nucleus Lower energy ___________ the nucleus Higher energy __________ the nucleus DOES NOT explain electron path as “orbiting like planets around the sun”

De Broglie and the Quantum Mechanical Model Wave-like motion of electrons: all moving particles have wave-like motion that restricts how much energy the electrons can absorb and emit (QUANTUM)

Schrodinger and the Quantum Mechanical Model Atomic Orbitals: 3D space electrons are likely to be found SHAPES electron fly in

Quantum Mechanical Model continued Principal Quantum Number (n)= #’s assigned that correlates with: Size Speed of electron Distance from the nucleus Amount of energy electron has COLOR AND LABEL A PERIODIC TABLE

Atomic Orbitals

Quantum Mechanical Model cont. Principle Energy Level= correlates with the distance from the nucleus and amount of energy electron has. Electrons fill lowest energy levels first Energy sublevels= the number of orbitals in each energy level Electrons fill lowest energy orbitals first

s Sphere 1 2 p Dumbbell 3 6 d Clover 5 10 f Complex 7 14 Type of sublevel Shape # of orbitals (configurations) Max # of electrons s Sphere 1 2 p Dumbbell 3 6 d Clover 5 10 f Complex 7 14

Can you fill in the rest by looking at a Periodic table? Energy level or Principal Quantum Number Sublevels Max # of electrons 1 1s 2 2s, 2p 2,6 = 8 3 3s, 3p, 3d 2,6,10 = 18 4 5 6 7

Heisenberg Uncertainty Principle

Electron Configuration- Main Idea: A set of three rules can be used to determine electron arrangement in an atom. Aufbau principle Electrons occupy lowest energy level first. Pauli Exclusion Principle Electron have opposite spins if they are in the same orbital. Hund’s Rule Electrons occupy each orbital before pairing.

Practice Electron configuration of Sodium: Orbital Notation of Sodium: Noble Gas Configuration of Sodium:

Exceptions to the Rules Many transition metals don’t follow the rules Copper and Chromium are common examples