Atomic Structure and Theories Dalton Chemistry with Doc

Dalton 1.The atom is made up of identical particles throughout 2.Particles are indivisible 3.Atom is made up of mostly (+) charge 4.Solid Billiard Ball Model

J. J. Thompson “Plum Pudding model” 1. Discovered Electrons 2. Used the “Cathode Ray Tube” a.k.a. “Crookes tube” 3. Shot particle beams through a magnetic field 4. 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) foil 2. Saw that most particles went through undeflected 3. noticed some particles were deflected 4. concluded that the atom is made up of Small dense (+) charged particles and is mostly open space

Bohr Model 1. Places electrons outside the nucleus in specific locations called orbits 2. Orbits = Energy levels (n) = Periods (Remember That!) Energy Levels 1 st 2 nd 3 rd

Modern Atomic Theory “Wave Mechanical Theory, Electron Cloud” 1. Like the Bohr model but can’t place electrons in an exact location 2. Show the Most Probable Location

Atoms are composed of subatomic particles NameLocationChargeMass Protons (Nucleons) Nucleus+1 amu Neutrons (Nucleons) Nucleus01 amu ElectronsOutside nucleus in orbits -1/1836 amu AMU= Atomic Mass Unit Based on C 12 as the standard, therefore a proton 1 H 1 = 1/12 the Mass of Carbon

Calculating Protons, Neutrons and Electrons 6 C 12 atomic mass = protons + neutrons atomic number = number of protons = which identifies the element! (+), Nuclear Charge Assume….since all elements on the periodic table are Neutral, this must also represent the # of electrons.

When they form a bond Form and IonIt is called a…. MetalsLose Electrons(+)Ca(t)ion t=(+) Non-MetalsGain electrons(-)A(n)ion n=negative IONS

Isotopes 1. different form of the same element 2. Differ in the number of neutrons therefore, they have different masses 6 C 12 6 C 14 7 X 14 6 X 12 =P= =n= =e= =P= =n= =e=

Characteristics of Isotopes 1. Tend to be unstable, therefore they emit energy which makes them radioactive 2. 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) 6 C C 12

Calculate the Atomic mass of carbon that is made up of 80% Carbon 12, 15% Carbon 10 and 5% Carbon 14? Change % to decimal, multiply by the mass, then add..80 X 12 = X 10 = X 14 = amu

Lewis Dot Diagrams 1. show only valence electrons 2. 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 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 X X

Electron Configurations 1. remember all configurations are located under the elements symbol 2. configurations show you a. total number of electrons b. number of occupied energy levels = periods c. # of valence electrons Ca 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 energy Absorb energy Release energy Bundle of Energy called a QuantaBright line Spectrum

17 Cl energy levels (period 3) Group 17 7 valence electrons

Spectral lines – identify the unknown