Law of multiple proportions

If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.

Another way to say this is:

A law proposed by Dalton which states that when elements combine, they do so in the ratio of small whole numbers. For example carbon and oxygen react to form CO or CO₂, but not CO_1.8.

Law of Multiple Proportions

proton 

p+ or p

in nucleus

positive charge

number defines atom

number above symbol on periodic table 

neutron 

n

neutral

in nucleus

purpose is to be mass in atom 

electron 

e-

orbit around the nucleus

negative charge 

neutral atom 

all stable atoms

number of protons (p/p+) is equal to number of electrons (e-) 

atomic number 

Z 

number of protons (p/p+)

number above the symbol on the periodic table 

atomic 

mass number 

A

weight of the atom

number of protons + the number of neutrons 

isotope 

literally: same type

same element, different mass due to different number of neutrons 

symbol 

eg: ^1H 

abbreviation used to represent an atom on the periodic table

the number to the upper left of the symbol is the mass number 

ion 

atom with unequal ratio of protons (p/p+) and electrons (e-)

can be positively charged or negatively charged 

light 

 has both wave properties and particles

visible light is only a small part of the spectrum

[image]

wavelength 

symbol: ___

the distance between 2 crests 

amplitude 

symbol: A

the maximum displacement from the mean position 

frequency 

symbol: v

the number of crests that pass a point per second 

higher frequency means shorter wavelengths

purple is the highest frequency, while red is the lowest

photons 

particles that make up a stream (wave) of light

energy of the photons is related to the frequency of the waves:

E=hv (energy (E) = Plank's Constant (h) x frequency (v) 

energy of photons in relation to  speed

v= c/__ (velocity = velocity of light/ wavelength)

velocity of light 

in the equation v = c/___ (wavelength)

c = 3.00 x 10^8 m/s 

Planck's Constant 

h

as in the equation: E = hv

h = 6.63 x 10^-34 j/s 

Bohr Theory 

electrons (e-) have discrete energy levels

e- are in orbits and that have specific energies

this explains light absorption and emission 

early theory of atomic structure

explains postion of e- in relation to the nucleus

only performed on H (hydrogen) 

the farther away from the nucleus the e-, the energy level

Quantum Mechanical Model 

replaced Bohr's model because Bohr's only worked for a few atoms because (he used hyrogen)

-e (electrons) can be found anywhere within a shell, not just in a ring

each -e (electron) is associated with a set of 4 quantum numbers 

Principal Quantum Number 

n

  labels the energy levels of hydrogenic atoms. It is the first in a set of numbers that show the unique quantum state of an electron

Pauli exclusion principle

Angular Momentum Quantum Number

l (cursive)

Magnetic Quantum Number 

ml (cursive, lowercase "l")

describe the unique quantum state of an electron

Spin Quantum Number 

Ms

n 

Bohr's orbit 

n + l rule 

e- (electrons) increase in energy as the sum of n+l increases 

e- closer to the nucleus have lower energy and those farthest from the nucleus have highest 

Degenerate e- (electrons) 

Have the same energy 

Shell 

a group of electrons in an atom all having the same  n ( principal quantum number)

subshell 

e- (electrons) of an atom with the same n + l 

e- in same shell 

2 e- (electrons) having the same n, l, and ml are said to be in the same orbit 

Classification of Orbitals 

to make classification easier, orbitals are assigned letters based on the value of l (angular momentum quantum number)

Values of l 

• s = 0
• p = 1
• d = 2
• f = 3

Heisenberg's Uncertainty Principal 

the statement that locating a particle in a small region makes the momentum of the particle uncertain, and conversely, measuring the momentum of a particle precisely makes the position uncertain

only the probable location can be calculated 

Maximun number of e- (electrons) per orbital 

• s = 2
• p = 6
• d = 10
• f = 14

Orbital Diagrams 

e- orbitals are filled as per energy levels and the Pauli Exclusion Principle, the Aufbau Principle  and Hund's Rule

Pauli Exclusion Principle 

no atomic orbital can contain more than 2 e-

if e- are in the same orbital, they must have opposite spin 

Aufbau Principle 

e- go to the lowest energy level first, before filling another energy level 

Hund's Rule 

every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.