Download 3b Atomic Theory Overview Unit 3b OVERVIEW atomic theory

Unit 3 OVERVIEW: Atomic Theory
Important concepts:
1. Atoms are made up of electrons, neutrons, and protons. Electrons are small and have a negative charge and are found in orbitals.
Protons are large and are found in the nucleus and are positive. Neutrons are large and found in the nucleus and have no charge.
2. Credit for the discovery of the electron is given to JJ Thompson. Credit for the discovery of the proton is given to Ernest
Rutherford.
3. Atomic number is the number of protons in the nucleus. Atomic mass is the average number of protons and neutrons in the
nucleus. Mass number is simply the number of protons and neutrons added together. Isotope is the same element but with a different
number of neutrons. We give a proton and neutrons a mass of one AMU.
4. Nuclear Symbols
X is the symbol for the element
A is the mass number
Z is the atomic number.
5. 15. Average Atomic Mass is the average mass of all of the isotopes. Nitrogen-14 has a mass of 14.003074amu and is 99.63%
abundant. Nitrogen-15 has a mass of 15.000108amu and is 0.37 % abundant. This is the solution for nitrogen: (14.003074amu)
(0.9963) + (15.000108amu) (0.0037) = 14.007 amu
6. Pauli Exclusion Principle- No more than 2
electrons can occupy the same orbital and no 2
electrons can have the same set of quantum
numbers.
7. Aufbau Principle - Electrons always fill orbitals
with the lowest energy first. Electrons fill orbitals in
a way to minimize the energy of the atom.
Therefore, the electrons in an atom fill the principal
energy levels in order of increasing energy (the
electrons are getting farther from the nucleus). The
order of levels filled looks like this: 1s, 2s, 2p, 3s,
3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,
and 7p.
8. Hund’s Rule- each electron will first fill all the
suborbitals with similar energy before pairing with
another electron in a half-filled orbital.
9. Orbital (Spin) diagram is a visual way to reconstruct the electron configuration by showing
each of the separate orbitals and the spins on the electrons. This is done by first determining the
subshell (s,p,d, or f) then drawing in each electron according to the stated rules above.
10. Wavelength () is from crest to crest. Amplitude is from mid line to the height of the wave. Frequency (f) is how
many waves pass a certain point usually per second. Speed of light = 3 x 108meters/second
11. When energy is added to an electron it will go from ground state to excited state. When it drops back to ground state
energy is released in the form of light.
12. c = f 1) c is the symbol for the speed of light, the speed at which all electromagnetic radiation moves when in a
perfect vacuum. (3.00 x 108 m/s) 2) λ is the Greek letter lambda and it stands for the wavelength of light. Wavelength is
defined as the distance between two successive crests of a wave. When studying light, the most common units used for
wavelength is nanometer, because it is so small. The official unit used by SI is the meter, so you must convert to it first.
Keep in mind that one nanometer equals 10-9 meters. 3) f stands for the frequency of the light wave. Frequency is defined
as the number of wave cycles passing a fixed reference point in one second. When studying light, the unit for frequency is
called the Hertz (its symbol is Hz). One Hertz is when one complete cycle passes the fixed point, so a million Hz is when
the millionth cycle passes the fixed point. There is an important point to make about the unit on Hz. It is NOT commonly
written as cycles per second (or cycles/sec), but only as sec-1 (more correctly 1/s, or Hz ). The "cycles" part is deleted,
although you may see an occasional problem which uses it.
What is the frequency of light having a wavelength of 555 nm? f = 5.40 x 1014 s-1
13. E = hf 1) E is the energy of the particular bundle of energy for that independent electromagnetic wave. 2) h stands
for a fundamental constant of nature now known as Planck's Constant. The value for Planck's Constant is
6.6260755 x 10-34 Joule second. Please note that the unit is Joule MULTIPLIED BY second. It is not a division, both
Joule and second are in the numerator. 3) f is the frequency of the particular photon being studied. The discussion about
frequency above applies here.
How many Joules of energy are contained in the light with λ = 550 nm? 3.612 x 10-19 J