CHEM 101 Chapter Notes - Chapter 2: Atomic Number, Noble Gas, Photon
Orbitals
Dalton’s Theory
I. 4 parts:!
A. All matter is made of atoms. Atoms are indivisible & indestructible!
B. All atoms of a given element have identical masses & properties!
C. Compounds are formed by a combination of 2+ different kinds of atoms!
D. A chemical reaction is a rearrangement of atoms!
A & B are false; smaller particles exist!
C & D are correct!
J.J. Thompson
I. Different charges (+) and (-) attract!
II. Like charges (+) and (-) repel!
III. Bent beam & negative magnet!
Rutherford’s Gold Foil Experiment
I. Most passed through b/c most of the atom is empty space!
II. Some deflected—-> hit by positive nucleus —-> dense and big!
A. His model had empty space and negative electrons, which is correct, but had no orbit,
which was incorrect !
Niels Bohr
I. Electrons don’t just float around, they have a distinct orbit!
Orbitals Theory
I. Orbital!
A. Region with electrons!
B. Different shapes and sizes that are determined by mathematical probabilities!
Pauli Exclusion Principle
I. One interpretation!
A. Each orbital can hold 2 electrons!
B. Electrons in same orbital must have opposite spins!
Types of Orbitals
*** One orbital can hold up to two electrons. Different types of orbitals have different #s
of orbitals
I. S orbital!
A. 1 orbital (# of lines for orbital diagram)!
B. Holds up to 2 electrons!
II. P orbital!
A. 3 orbitals (# of lines for orbital diagram)!
B. Holds up to 6 electrons!
III. D orbital!
A. 5 orbitals (# of lines for orbital diagram)!
B. Holds up to 10 electrons!
IV. F orbital!
A. 7 orbitals (# of lines for orbital diagram)!
B. Holds up to 14 electrons!
Bohr’s Postulate
I. Each energy level can hold a maximum of 2n2 electrons!
II. n= energy level!
III. Examples!
A. 1st energy level: 2 12*2=2!
B. 2nd energy level: 8 22*2=8!
Aufbau Principle
I. You will always start with the orbitals that have the lowest energy and build up from there!
A. The lowest energy orbital in a particular energy level is s2 then p…!
###### 1s1!
###The base one represents the energy level (shell)!
###The letter represents the type of orbital (sub-shell)!
###The exponent represents the number of electrons in the orbital!
I. Each orbital is represented with a line _________!
A. 1 line for the S orbital!
B. 3 lines for the P orbital!
C. 5 lines for the D orbital!
D. 7 lines for the F orbital!
Hund’s Rule
I. Fill each degenerate orbital before pairing electrons in order to minimize repulsion!
A. (P” orbital has room for 6 arrows, but you have to put one in each box before you put
two in one, which have to face opposite directions!
Electron Configuration
I. Complete!
A. Write out the entire thing from 1s2 to the element term!
II. Shorthand!
1. Take just the last term!
III. Noble Gas!
A. Take the noble gas (last box) from the upper row and do the complete list until you get
to the element!
IV. Orbital Diagram!
1. “S” orbital only has room for 2 arrows!
2. “P” orbital has room for 6 arrows!
3. “D” orbital has room for 10 arrows!
4. “F” orbital has room for 14 arrows!
Energy Level
# of electrons
Orbital Present
1
2
1s
2
8
2s, 2p
3
18
3s, 3p, 3d
4
32
4s, 4p, 4d, 4f
Light and Energy
I. 3 Primary Characteristics of Light!
A. Wavelength $(λ)— distance of one complete cycle!
B. Frequency (v)— number of cycles past a given point!
C. Speed of light (c)— 3.0 x 108 m/sec!
I. Inverse Relationship between wavelength and frequency !
A. Short wavelength — high frequency!
B. Long wavelength — low frequency!
Equation λ x v = c!
#λ— meters!
#v— Hz!
#c— m/sec!
I. Electromagnetic Spectrum!
A. 1m = 109 nm (visible light)!
When energy travels towards the left, towards gamma rays, it is increasing; when
traveling towards the right, energy is decreasing!
Frequency and wavelength of visible light:!
Document Summary
Orbitals: all matter is made of atoms. Atoms are indivisible & indestructible: all atoms of a given element have identical masses & properties, compounds are formed by a combination of 2+ di erent kinds of atoms, a chemical reaction is a rearrangement of atoms. A & b are false; smaller particles exist. J. j. thompson: di erent charges (+) and (-) attract. Rutherford"s gold foil experiment: most passed through b/c most of the atom is empty space. Some de ected -> hit by positive nucleus -> dense and big: his model had empty space and negative electrons, which is correct, but had no orbit, which was incorrect. Niels bohr: electrons don"t just oat around, they have a distinct orbit. Orbitals theory: orbital, region with electrons, di erent shapes and sizes that are determined by mathematical probabilities. Pauli exclusion principle: one interpretation, each orbital can hold 2 electrons, electrons in same orbital must have opposite spins.
