Unit 3 Atomic Theory

Atom Smallest particle possessing the properties of an element.

Nucleus Dense, positively charged central region that contains protons and neutrons.

Protons Positively charged subatomic particles that are found in the nucleus

Neutrons Neutral subatomic particles (have no electrical charge) that are found in the nucleus.

Electron Cloud Different energy levels surrounding the atom’s nucleus where electrons can be found.

Electrons Negatively charged subatomic particles that surround the nucleus.

Atomic Number The number of protons in an atom.

Atomic Mass The relative average mass of an atom of an element as found in nature. Atomic mass = # of protons + # of neutrons.

II: Atomic Particles ParticleMassLocationCharge Proton 1 AMU NucleusPositive Neutron NucleusNeutral Electron 0 AMU Electron cloud Negative

Isotopes Atoms of the same element that have a different number of neutrons.

Isotopes  Two (2) or more atoms of the same element with a different mass.  Percent (%) abundance: Protium, Deuterium, Tritium %, 0.015%, 0%

Self Check 1.What two subatomic particle are found in the nucleus? A. Neutrons and Electrons B. Protons and Electrons C. Neutrons and Protons D. Neutrons only D. Neutrons only

Self Check 2.The atomic number is equal to the _______. A. Number of neutrons in an atom. B. Number of electrons in an atom. C. Number of neutrons plus the number of protons in an atom. D. Number of protons in an atom.

Self Check 3.Isotopes are atoms of the same element that have a different number of ______. A. Neutrons B. Protons C. Electrons D. All of the above

Self Check 4.The element with an atomic number of 14 is? A. Nitrogen B. Silicon C. Aluminum D. Sulfur

Important Number Stuff  Atomic number is equal to the number of protons (and electrons in a neutral atom)  Atomic Mass is the sum of protons and neutrons

Examples… Element # protons # neutrons # electrons Ave. Atomic mass Boron Sulfur Gold

Sample—look at “2_weighted ave.”  Of 100 marbles: –25 have a mass of 2.00g –75 have a mass of 3.00g –What is the average mass?  25% = % = 0.75  (0.25 x 2.00) + (3.00 x 0.75) = Ave Mass  = 2.75

Sample with Atoms  Copper 63 amu = 69.17%  Copper 65 amu = 30.83%  Calculate the Average atomic mass

Continued…  Copper 63 amu =  Copper 65 amu =  Calculate the Average atomic mass  (63 x ) + (65 x )  AMU –Check on periodic table

Ions Electrically charged atoms or groups of atoms. Cations = positively charged Anions = negatively charged

I: Models of the atom over time  Democritus: fifth century BC Philosopher –First to describe matter as made of tiny particles  John Dalton: “Billiard ball” theory 1803 –Atom = small solid sphere  In an element = all the same “sphere”  Different elements = different “sphere”  Compounds = different spheres combined in different ratios

Continued…  JJ Thompson: 1897 “Plum Pudding” model –Atom = sphere of + and – particles –Discovered the electron = Nobel prize

Valence Electrons Electrons found in the outer-most energy level of the electron cloud. Identify patterns using periodic table based on element location

Continued  Ernest Rutherford: 1908 –Atom = mostly empty space  + nucleus  - electrons outside  Niels Bohr: 1913 –Electrons traveled in circular orbits

Continued…  Electron Cloud Model: 1920’s –Atom = Dense nucleus of + protons and neutral neutrons. –Electrons surround nucleus in “clouds” of different NRG levels. (NRG =Numerical Renormalization Group)

Elements on the Periodic Table 1 Hydrogen H 1.008

Self Check 5.Draw a picture of what Iron in its neutral state would look like on the periodic table. Hint:

Self Check Answers 1. C 2. D 3. A 4. B Iron Fe 55.85

III. Molar Conversions III. Molar Conversions

A. What is the Mole?  A counting number (like a dozen)  Avogadro’s number (N A )  1 mol = 6  items A large amount!!!!

 1 mole of hockey pucks would equal the mass of the moon! A. What is the Mole?  1 mole of pennies would cover the Earth 1/4 mile deep!  1 mole of basketballs would fill a bag the size of the earth!

B. Molar Mass  The mass of 1 mole of an element or compound. Round to nearest whole number (except chlorine)  Atomic weight label: –amu/atom or g/mol  Molecular weight label: –amu/molecule or g/mol

B. Molar Mass Examples  carbon  aluminum  zinc 12 g/mol 27 g/mol 65 g/mol

B. Molar Mass Examples  water  sodium chloride –H2O–H2O–H2O–H2O –2(1) + 16 = 18 g/mol –NaCl – = 58.5 g/mol

B. Molar Mass Examples  sodium bicarbonate  sucrose –NaHCO 3 – (16) = 84 g/mol –C 12 H 22 O 11 –12(12) + 22(1) + 11(16) = 342 g/mol

C. Molar Conversions molar mass (g)(g) MASS IN GRAMS MOLES NUMBER OF PARTICLES 6  (atoms/molecules)

C. Molar Conversion Examples  How many moles of carbon are in 26 g of carbon? 26 g C 1 mol C 12 g C = 2.17 mol C

C. Molar Conversion Examples  How many molecules are in 2.50 moles of C 12 H 22 O 11 ? 2.50 mol C 12 H 22 O 11 6  molecules 1 mol = 1.5  molecules molecules C 12 H 22 O 11 C 12 H 22 O 11

C. Molar Conversion Examples  Find the mass of 2.5 moles of NaHCO mol NaHCO 3 84 g 84 g 1 mol = 210 g NaHCO 3

Patterns on the Periodic Table