Atomic Structure and Theories

Dalton

Chemistry with Doc

Dalton1.The atom is made up of identical

particles throughout2.Particles are indivisible3.Atom is made up of mostly (+) charge4.Solid Billiard Ball Model

J. J. Thompson “Plum Pudding model”

1. Discovered Electrons2. Used the “Cathode Ray Tube” a.k.a. “Crookes tube”3. Shot particle beams through a magnetic field4. Concluded that the beams were made up of

particles with a negative charge…..called electrons

Rutherford “Gold foil experiment”1. Shot alpha particles (+) through a gold (Au) foil2. Saw that most particles went through undeflected3. noticed some particles were deflected4. concluded that the atom is made up of

Small dense (+) charged particles and is mostly open space

Bohr Model1. Places electrons outside the nucleus in specific locations called orbits2. Orbits = Energy levels (n) = Periods (Remember That!)

Energy Levels 1st

2nd

3rd

Modern Atomic Theory “Wave Mechanical Theory, Electron Cloud”

1. Like the Bohr model but can’t place electrons in an exact location2. Show the Most Probable Location

Atoms are composed of subatomic particles

Name Location Charge Mass

Protons (Nucleons)

Nucleus + 1 amu

Neutrons (Nucleons)

Nucleus 0 1 amu

Electrons Outside nucleus in orbits

- 1/1836 amu

AMU= Atomic Mass UnitBased on C12 as the standard, therefore a proton 1H1 = 1/12 the Mass of Carbon

Calculating Protons, Neutrons and Electrons

6C12 atomic mass = protons + neutrons

atomic number = number of protons = which

identifies the element!

(+) , Nuclear ChargeAssume….since all elements on the periodic table areNeutral, this must also represent the # of electrons.

When they form a bond

Form and Ion It is called a….

Metals Lose Electrons (+) Ca(t)ion

t=(+)

Non-Metals Gain electrons (-) A(n)ion

n=negative

IONS

Isotopes1. different form of the same element2. Differ in the number of neutrons therefore, they have different masses

6C126C14

7X146X12

=P==n==e=

=P==n==e=

Characteristics of Isotopes1. Tend to be unstable, therefore they emit energy which makes them radioactive2. There are no stable isotopes above element #82

Atomic Mass vs Mass #(the sum of the weighted avg. of all naturally occurring isotopes P + N

(Whole number)

6C12.0171

6C12

Calculate the Atomic mass of carbon that is made up of80% Carbon 12, 15% Carbon 10 and 5% Carbon 14?

Change % to decimal, multiply by the mass, then add.

.80 X 12 = 9.6

.15 X 10 = 1.5

.05 X 14 = 0.7 11.5 amu

Lewis Dot Diagrams1. show only valence electrons2. remember…group number = valence electrons 1 =1, 2 =2, 13 = 3, 14 = 4, 15 = 5 etc.3. remember the last number in the configuration also equals # of valence electrons

Cl 2-8-7 valence electrons

3 energy levels This tells you:

3 energy levels are occupied (Cl is in per. 3) 7 valence electrons (Grp 17)

H He Li Be

B C N O

F Ne

XX

Electron Configurations

1. remember all configurations are located under the elements symbol

2. configurations show you a. total number of electronsb. number of occupied energy levels = periodsc. # of valence electrons

Ca . . 2-8-8-2 2 valence electrons Ca 18 kernel electrons

4 energy levels occupied

Remember, after element #20 (Calcium), we then start to fill in the d block which are the transitional metals.

(not so important)

Ground State vs Excited State

• Ground State• Stable• Lower energy

• Lower Energy

• Excited State• Unstable• Higher Energy State

• Higher energyAbsorb energy

Release energy

Bundle of Energy called a Quanta Bright line Spectrum

17Cl35

2-8-7

3 energy levels (period 3)Group 177 valence electrons

Spectral lines – identify the unknown