Timeline of Atomic Theory Make sure it has

Dates (some may not have dates) Important Peoples Names What they found/discovered/believed to be true The experiment they did Picture of the model they developed (if there is

one)

The AtomWhat is it made of???

Protons Positively charged Mass = 1 amu = 1.67 x10-24 grams Located in the nucleus Gives an atoms its identity (atomic number)

Neutrons Neutral charge Mass = 1 amu =1.67 x10-24 grams Located in the nucleus Different numbers of neutrons define isotopes

Electrons Negative charge Mass = 1/1840 amu = 9.11 x10-28 grams Located outside the nucleus (energy levels,

shells, orbitals) Equal to the number of protons in a neutral

atom Loss or gain of electrons gives ions their

charge

Isotopes The identity of the element depends on the

number of protons Atoms of the same element can have different

number of neutrons. Atoms of the same element that has different

number of neutrons have different masses.

Isotope Designation

11H

12H

13H

92235U

Mass number

Atomic numberElement Symbol

*Nuclides of Hydrogen*Nuclides of Hydrogen

More Isotope Designation

They They bothboth have have 66 protons. protons.

Carbon-12 Carbon-14 Carbon-12 Carbon-14

6 6 neutrons neutrons 88 neutrons neutrons

Plutonium-241Plutonium-241(Name of element- mass number)

# neutrons = Mass # - atomic ## neutrons = Mass # - atomic #

Atomic Number Gives an atom its identity # Protons The whole number in bold type in each element

square (1)

Cl

17 35.453

Chlorine

Atomic Mass The mass average of all naturally occurring

isotopes of an element The number expressed as a decimal in each

element square

Na11 22.990

Sodium

Determination of Atomic Mass There are three isotopes of oxygen; and their relative

abundances: Oxygen -16 99.759 % Oxygen-17 0.037 % Oxygen-18 0.204 %

Lets figure out the atomic weight of oxygen together!

Mass Number Sum of the protons + neutrons Always a whole number

Representation

C 12

6

M

AX

Mass Number

Atomic Number

Symbol

Electron Energy Levels 1 has a maximum of 2 electrons

Both in the “s” sublevel 2 has a maximum of 8 electrons

2 in the “s” sublevel 6 in the “p” sublevel

3 has a maximum of 18 electrons 2 in the “s” sublevel 6 in the “p” sublevel 10 in the “d” sublevel

Electron Energy Levels (cont.) 4 has a maximum of 32 electrons

2 in the “s” sublevel 6 in the “p” sublevel 10 in the “d” sublevel 14 in the “f” sublevel

Electron Configurations Hydrogen – has only one electron in the first

energy level and the first sublevel

1 H: 1s1

Helium – has 2 electrons in the first energy level filling it to capacity

2 He: 1s2

Electron Configurations (cont.) Lithium – has 2 electrons in the first energy level

and one in the second

3 Li: 1s22s1

Be – has 2 e- in the first energy level and 2 in the second but they both go into the “s” sublevel

4 Be: 1s22s2

Electron Configurations (cont.) Carbon – has 2 electrons in the first energy level and

four in the second

6C : 1s22s22p2

Fluorine – has 2 e- in the first energy level and 5 in the second but they go into both the “s” & “p” sublevels

9F: 1s22s22p5

Rules for Orbital Diagrams for an Atom Aufbau – electrons fill lowest energy levels

first ( follow the diagonal rule) Pauli Exclusion Principle- There can only be

2 electrons in an orbital Hund’s Rule – electrons fill equal energy

orbitals with one first before they pair

Orbital Diagram for A Nitrogen Atom

N

1s 2s 2p 3s

Orbital Diagram for A Fluorine Atom

F

1s 2s 2p 3s

Orbital Diagram for A Magnesium Atom

Mg

1s 2s 2p 3s