Atomic Number Number of Protons Always an integer!

Mass Number Number of Protons + Neutrons Always an integer!

12 C Left Superscript = mass number 6

12 C Left Subscript = atomic number 6

80 Br 35 Atomic Number = ?

20 Ne Mass Number = ?

27 Al Mass Number = ?

40 Ca 20 Atomic Number = ?

# of electrons in a neutral atom? Neutral atoms have the same number of electrons and protons.

Isotope Atoms of the same element with a different # of neutrons Same # of protons, different # of neutrons Same atomic #, different mass # 6 C and 6 C 12 14

Characteristics of Proton Charge = +1, mass = 1 amu, location = inside nucleus

Characteristics of Neutron Charge = 0, mass = 1 amu, location = inside nucleus

Characteristics of Electron Charge = -1, mass = 1/1836 amu or amu, location = outside nucleus

Summary of facts for subatomic particles Relative Mass (amu)Relative ChargeLocation Proton or  1+1Nucleus Neutron or  10Nucleus Electron or  or  0 Outside Nucleus

Ion An atom that has gained or lost electrons & so carries charge

Positive Ion An atom that has LOST electrons

Negative Ion An atom that has GAINED electrons

Charge # protons - # electrons

Nucleons Protons & Neutrons

atom Smallest bit of an element that retains the properties of the element.

atom Smallest bit of an element that can participate in a chemical reaction.

# of neutrons Mass number – atomic number Subtract the atomic number FROM the mass number!

14 C 8 neutrons 6 protons 6 electrons 6 # of neutrons = ? # of protons = ? # of electrons = ?

9 Be 5 neutrons 4 protons 4 electrons 4 # of neutrons = ? # of protons = ? # of electrons = ?

40 Ar 22 neutrons 18 protons 18 electrons 18 # of neutrons = ? # of protons = ? # of electrons = ?

15 N 8 neutrons 7 protons 7 electrons 7 # of neutrons = ? # of protons = ? # of electrons = ?

24 Mg Right superscript = charge 12 2+

15 N 8 neutrons 7 protons 10 electrons (gained 3) 7 # of neutrons = ? # of protons = ? # of electrons = ? -3

19 F 10 neutrons 9 protons 10 electrons (gained 1) 9 # of neutrons = ? # of protons = ? # of electrons = ?

16 O 8 neutrons 8 protons 10 electrons (gained 2) 8 # of neutrons = ? # of protons = ? # of electrons = ? -2

23 Na 12 neutrons 11 protons 10 electrons (lost 1) 11 # of neutrons = ? # of protons = ? # of electrons = ? +1

24 Mg 12 neutrons 12 protons 10 electrons (lost 2) 12 # of neutrons = ? # of protons = ? # of electrons = ? +2

27 Al 14 neutrons 13 protons 10 electrons (lost 3) 13 # of neutrons = ? # of protons = ? # of electrons = ? +3

Nuclear Charge Charge on the nucleus only. Does not include the electrons. Always positive. Equals the number of protons. Equals the atomic number.

Cation Positive ion

Anion Negative ion

Dalton’s Model Billiard Ball Model Solid Indivisible Homogeneous

Dalton’s model 1.All matter is composed of atoms. 2.Atoms of a given element are identical, atoms of different elements are different.* 3.Atoms cannot be subdivided, created, or destroyed.* 4.Atoms of different elements combine in small whole number ratios to make compounds. 5.In chemical reactions, atoms are rearranged.

Thomson’s Model Plum Pudding Model Solid Divisible Inhomogeneous: contain charges! Electrons are particles!

Deflection of cathode ray No deflection in field free region Deflection in electrostatic field Deflection in magnetic field

Thomson’s model Thomson gets credit for discovering electron because he got the first “numbers” – he found the charge-to-mass ratio of the electron.

Rutherford’s Model Nuclear Model Mostly empty space Divisible Inhomogeneous Contains a small, dense positive nucleus

Rutherford’s model Nuclear Model

Rutherford’s Experiment Shot αlpha particles at gold foil. 1.Most went through, so most of the atom is empty space. 2.Some deflected back by small dense positive nucleus.

Rutherford’s Experiment Most of the alpha particles went through so most of the atom is empty space A very small percent of the alpha particles deflected back: Evidence for a small, dense, positive nucleus.

Bohr’s Model Shell Model

Bohr’s Model Shell Model Electron is still a particle. Quantized energy levels. Electrons move on 3-D spherical orbits.

Bohr Configurations In the NYS Reference Tables! Bohr configurations are “irregular” because the Bohr model is incorrect. You cannot predict them for the larger atoms, even if you know the maximum capacities of each orbit.

Bohr Diagram Sulfur: p Valence electrons are in outermost orbit

Bohr Configuration Maximum Capacity of Orbits Orbit, nMaximum Capacity n2n 2 Sulfur: occupied levels but only two completely occupied levels. Read question with care!

Schrodinger’s Model Wave Mechanical Model Electron is treated as a wave. Electron Energy is Quantized. Most probable location = orbitals.

Schrodinger’s Model Wave Mechanical Model

Lewis Dot Diagrams for Atoms Use dots or x’s to represent the valence electrons. The symbol represents the nucleus and all the inner shell electrons – this is the kernel of the atom. In NYS, the # of dots has to match the # of valence electrons.

Lewis Dot Diagrams

atomic mass The mass of the entire atom: includes protons, neutrons, electrons. Expressed relative to the mass of a Carbon-12 atom.

atomic mass unit 1 atomic mass unit  1/12 the mass of a C-12 atom. or The C-12 atom has a mass of atomic mass units.

Isotopic Mass Mass of one specific isotope Notice that these are decimals! Why is C-12 exactly …? Because C-12 is the standard! Note: we use these rarely! Table of Isotopic Masses:

Average atomic mass The weighted average of the masses of the naturally occurring isotopes of an element. What are these masses in the periodic table? Warning: chemists get sloppy & call this atomic mass.

Average atomic mass 1)Convert % abundance to decimal format. 2)Multiply abundance factor by appropriate mass. 3)Sum

Quick check on average atomic mass calculation. 1)Final answer must be between the highest & lowest masses. 2)Final answer will be closest to mass of most abundant isotope.

Calculate the average atomic mass of Cl. 1)75% =.75 and 25% =.25 2)(.75) X 35 = and (.25) X 37 = ) = 35.5 = avg. atomic mass of Cl 4)Ans is between 35 & 37, but closer to 35. Convert % to decimal Multiply each abundance factor by appropriate mass Add up all the terms Quick check. Report to tenths place. IsotopePercent Abundance Cl-3575% Cl-3725% Note: The NYS Regents make severe approximations to the isotopic masses! So no worries about sig figs!

Law of Conservation of Mass for ordinary chemical and physical change Mass is neither created nor destroyed Total Mass Before = Total Mass After Total Mass Reactants = Total Mass Products

Law of Conservation of Mass for ordinary chemical and physical change O 2 + 2H 2  2H 2 O 32 grams of oxygen reacts with X grams of hydrogen yielding 36 g of water. 32 g + X g = 36 g X = 4 g Recall: in this kind of problem you do NOT use the coefficients!

Chemical Equations Reactants  Products aA + bB  cC + dD A & B are reactants. C & D are products.

Law of Definite Proportions A chemical compound contains the same elements in exactly the same proportions by mass regardless of sample size or source.

Law of Definite Proportions NaCl is 39.3% Na and 60.7% Cl no matter how big the sample or where it is from

Law of Multiple Proportions When two or more different compounds are composed of the same two elements, then the ratio of the mass of the second element combined with a certain fixed mass of the first element is always a ratio of small whole numbers.

Law of Multiple Proportions Normalized Data! Grams MnGrams O Compound A17.16 g5.00 g Compound B12.87 g5.00 g Compound C11.44 g5.00 g This is the fixed mass, so you can forget about it! Take ratios of the Mn masses! A/B = 17.16/12.87 = 1.33 = 4/3 A/C = 17.16/11.44 = 1.5 = 3/2 B/C = 12.87/11.44 = = 9/8

Relative atomic mass Both atomic mass units and the mole are based on C-12.

Relative atomic mass Dual Perspective Microscopic vs. Macroscopic

Relative atomic mass Take the relative atomic mass from the periodic table and 1.Stick “atomic mass unit” after it to get the average mass of one atom or 2.Stick “gram” after it to get the mass of one mole of that element.

Mole Measure of the amount of substance in terms of the number of particles. The amount of any substance that contains as many particles as there are atoms in 12 grams of pure 12 C.

Dual Perspective The average Li atom has a mass of atomic mass units. A mole of Li atoms has a mass of grams.

mole 6.02 X Avogadro’s Number

Molar Mass Mass of one mole of a substance. For elements, the molar mass is the relative atomic mass expressed in grams.

# of moles from Table T. # of moles = Mass of sample Molar Mass

1 Mole 6.02 X 10 23

0.5 Mole 3.01 X 10 23

0.25 Mole 1.50 X 10 23

2.0 Mole X Or X 10 24