Energy and the Quantum Theory
Light electrons are understood by comparing them to light 1. radiant energy 2. travels through space 3. makes you feel warm Light has properties of waves and particles
Amplitude: height of a wave (intensity) Wavelength: distance between crests (λ) Frequency: number of wavelengths passing a point in a given amount of time (cycles/ sec., Hz) (ν) Speed: light ( 3.00 X 10 8 m/s = c)
λ = 633 nm (red) What is the frequency? Convert: 633nm x (1m / 1x10 9 nm)= 6.33x10-7 m Solve for v. v = c / λ ν = (3.00x10 8 m/s) / (6.33x10-7 m) = 4.74x10 14 Hz
Electromagnetic waves what light is Electromagnetic radiation 1. light 2. x-rays 3. gamma rays 4. radio waves
1. What is wavelength? 2. What is amplitude? 3. What is frequency? 4. What is the math relationship between wavelength and frequency? 5. What is electromagnetic radiation? 6. What are some types of waves other than light?
Planck proposed that a fixed amount of energy can be absorbed or emitted by atoms, and called the energy a quantum E = hν h = 6.63 x 10-34 J-s Planck s constant
Which one shows continuous energy and which one shows discrete?
Light causes electrons to shoot off metals not any kind of light will do Example: with Na red light never works but violet light always works
Photon: discrete particle of light electron can either use the photon or it can t; no partial use is allowed Energy of a photon is high when the frequency is high higher frequency is more dangerous low frequency is not dangerous
Light behaves as both a wave and a particle
1. What does Planck s constant teach us about atoms? 2. What is the photoelectric effect? 3. What is a photon? 4. Explain the duel nature of light.
Line spectrum: contains only certain colors or wavelengths Atomic emission spectrum: a line spectrum for the elements; fingerprint of elements, unique for each element
Electrons have certain orbits that correspond to quanta of energy Quantum number (n): energy level Ground state (n=1): lowest energy level, closest to nucleus Excited state (n>1): higher energy level, further from nucleus
When an electron absorbs energy from light, it jumps to a higher energy level. When it falls back to the ground state, it releases the energy as light.
DeBroglie proposed the idea of matter waves. Since light behaves like a wave and particle, matter should also act like a wave and particle. There is a dual nature to matter. Electron microscopes work because matter behaves like a wave.
The position and momentum of a moving object (electron) cannot be measured and known at exactly the same time. We can only tell the probability of finding it in a certain area.
1. What is the atomic emission spectrum? 2. Explain Bohr s model of the atom. 3. What happens when electrons change shells in an atom? 4. What did DeBroglie propose? 5. What is the Heisenberg Uncertainty Principle?
Quantum-mechanical model uses probability to describe electron motion Electron density cloud that shows the probability of finding an electron in a certain area
Area where electron is most likely to be found (90%) s spherical p dumbbell d four leaf clover f - complex
Principal energy levels described by quantum number (n) Sublevels n=1 1 sublevel 1s n=2 2 sublevels 2s, 2p n=3 3 sublevels 3s, 3p, 3d n=4 4 sublevels 4s, 4p, 4d, 4f 2s is bigger than 1s but same shape
Sublevel orbitals s 1 p 3 d 5 f 7
A spinning charge produces a magnetic field, so a spinning electron is like a little magnet. Opposite spins will cancel each other. Only two electrons can fit in an orbital. They are called paired electrons.
s 2 p 6 d 10 f 14
1. What is an electron orbital? 2. What shape is the S orbital? 3. How many orbitals are there? How many electrons can fit in each orbital? 4. How many different orbitals are there within the P orbital? The D orbital? 5. Why is an electron like a little magnet?
Show where electrons are located in the atom and how much energy they possess.
Electrons are added one at a time to the lowest energy orbitals available until all electrons have been accounted for. Examples: C has 6 electrons Cl has 17 electrons
There can only be two electrons per orbital; they must have opposite spins. ( paired & unpaired electrons)
Electrons fill up orbitals in the same sublevel with one electron before they pair up.
1. What is the Aufbrau Principle? 2. What is the Pauli Exclusion Principle? 3. In what order to the orbitals fill up? Start with 1s and end with 3d. 4. What is Hund s rule?