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Chapter 2 Atoms, Molecules, Ions. HW: 4 11 23 25 31 35 39 45 50 53 55 59 61 63 65 67 69 71 102. 2.1 – Atomic Theory. Dalton’s Atomic Theory Elements are made of extremely small particles called atoms Atoms of an element are identical Atoms are not created or destroyed

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chapter 2 atoms molecules ions

Chapter 2Atoms, Molecules, Ions

HW: 4 11 23 25 31 35 39 45 50 53 55 59 61 63 65 67 69 71 102

2 1 atomic theory
2.1 – Atomic Theory

Dalton’s Atomic Theory

  • Elements are made of extremely small particles called atoms
  • Atoms of an element are identical
  • Atoms are not created or destroyed
  • Compounds are combinations of atoms

(1766-1844)

2 1 atomic theory1
2.1 – Atomic Theory

Law of Definite Proportions (ConstantComposition)

-Joseph Proust

-A compound always has the same proportion of its elements

Law of Conservation of Mass (Matter) = Matter cannot be created or destroyed

Law of Multiple Proportions

-Two or more compounds with the same elements must have different proportions of the elements

-Example: Water vs. Hydrogen peroxide

2 2 discovery of atomic structure
2.2 – Discovery of Atomic Structure

Atom = Basic unit of an element that can enter into a chemical reaction

Subatomic Particle = Particles that make up an atom (protons, neutrons, electrons are as small as we will study)

2 2 discovery of atomic structure1
2.2 – Discovery of Atomic Structure

-Cathode (Ray) Tube / Crooke’s Tube / = Glass tube w/2 metal plates. Connected to high voltage source. Emits ray.

Crooke – Determined that the ray was made of negative particles

2 2 discovery of atomic structure2
2.2 – Discovery of Atomic Structure

JJ Thomson = 1897 – Credited w/ finding electrons Determined charge to mass ratio to be -1.76  108 coulombs/g.

Millikan = 1909 - Performed the Oil Drop Experiment. Found the charge of an electron (-1.60 x 10-19C). Could then calculate mass of the electron

2 2 discovery of atomic structure3
2.2 – Discovery of Atomic Structure

Radioactivity = Spontaneous emission of radiation

a = + charge = Helium nucleus = High mass

b = - charge (high speed electrons) = Low mass

g = No charge. High energy = No mass

2 2 discovery of atomic structure4
2.2 – Discovery of Atomic Structure
  • 1900 - “Plum pudding” model, put forward by

JJ Thompson.

  • Positive sphere of matter with negative electrons imbedded in it.
2 2 discovery of atomic structure5
2.2 – Discovery of Atomic Structure

Protons = + charge particles in the nucleus

Rutherford = 1919- Gold Foil Experiment

-Most alpha particles when through, some deflected

2 2 discovery of atomic structure6
2.2 – Discovery of Atomic Structure

This proved that Thomson’s model was incorrect

Results of Gold Foil Experiment:

Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom.

-Most of the volume of the atom is empty space.

2 2 discovery of the structure of the atom
2.2 – Discovery of the Structure of the Atom

-We will only discuss protons, neutrons and electrons because they are the only ones that affect chemical behavior

-Charge on proton = +1.602 x 10-19 C. Assigned a +1 charge.

-Charge on an electron = -1.602 x 10-19 C. Assigned a -1 charge.

-Neutrons – Electrically neutral. Similar mass to protons. Discovered by Chadwick.

Mass of electron so small it is ignored

2 3 modern atomic theory
2.3 – Modern Atomic Theory

amu = atomic mass unit. 1 amu = 1.66054 x10-24 g. Based on 12 amu = mass of one atom of Carbon-12. 1 amu is approximately equal to the mass of a proton/neutron.

Angstrom (Å) = Unit used to measure atom size.

1 Angstrom = 1 x 10-10 m

2 3 modern atomic theory atomic numbers mass numbers and isotopes
2.3 – Modern Atomic TheoryAtomic Numbers, Mass Numbers and Isotopes

Symbols:

1.

2. Carbon - 12

Mass Number

2 3 atomic number etc
2.3 – Atomic Number, Etc.

Atomic Number:

All atoms of the same element have the same number of protons: The atomic number (Z)

2 3 atomic number etc1
2.3 – Atomic Number, Etc.

Mass Number:

The total number of protons and neutrons in the atom.

2 3 atomic number etc2

11

6

12

6

13

6

14

6

C

C

C

C

2.3 – Atomic Number, Etc.

Isotopes = Atoms of the same element with different masses.

-Isotopes have different numbers of neutrons.

-Isotopes have different mass numbers.

Carbon-11 Carbon-13

Carbon-12 Carbon-14

2 4 atomic weights
2.4 – Atomic Weights

Average Atomic Masses – Based on abundance of isotopes and mass of each isotope. =Atomic Weight

Example 2.4 – Page 47

2 5 periodic table
2.5 - Periodic Table

Periodic Table – Arranged by atomic number with elements with similar properties in same column.

Mendeleev – Organized first accepted Periodic Table

  • The rows on the periodic table are periods.
  • Columns are groups.
  • Elements in the same group have similar chemical properties.
periodic table
Periodic Table

Metals are on the left side of the chart.

-Low electronegativity

-Good conductors of heat and electricity

-Malleable, Ductile, Luster

-Readily lose electrons

periodic table1
Periodic Table

Nonmetals are on the right side of the periodic table (with the exception of H).

-High electronegativity

-Readily gain electrons

periodic table2
Periodic Table

Metalloids border the stair-step line (with the exception of Al and Po).

-Properties are intermediate between metals and nonmetals.

groups
Groups

1

2

16

17

18

These five groups are known by their names.

2 6 molecules and molecular compounds
2.6 – Molecules and Molecular Compounds

Chemical Formula = Shows the atoms present in a substance

Molecule – Two or more atoms in a definite arrangement held by covalent bonds. Can be the same or different atoms.

ex – H2, H2O, C6H12O6

Diatomic Molecule = Molecule made of only 2 atoms total

Molecular Compound – Must have DIFFERENT elements

ex- H2O is a compound, but H2 is NOT

2 6 molecules
2.6 – Molecules

REVIEW:

Bonds –

-Nonpolar Covalent – Equal sharing of electrons

-No partial charges

-Electronegativity of two atoms is close

-Difference of electronegativities is <0.3

-Polar Covalent – Unequal sharing of electrons

-Partial charges exist on atoms

-Electronegativity difference is 0.3-1.7

2 6 molecules1
2.6 - Molecules

Molecular Formula = Gives actual number and type of atoms in a molecule

Empirical Formula = Simplest whole number ration of atoms

Example = Glucose

2 6 molecules2
2.6 - Molecules

Structural Formula – Similar to a Lewis Structure. Shows bonds, but not shape.

slide28

2.7 – Ions and Ionic Compounds

  • When atoms lose or gain electrons, they become ions.
    • Cations are positive and are formed by elements on the left side of the periodic chart.
    • Anions are negative and are formed by elements on the right side of the periodic chart.
2 7 ions
2.7 - Ions
  • Examples:
2 7 ions1
2.7 - Ions

Ionic compounds (such as NaCl) are formed by ionic bonds. Contain both + and – ions.

Ionic bonds are generally formed between metals (cations) and nonmetals (anions).

Monatomic – one atom only with a charge

Polyatomic – more than one atom with an overall charge

metallic bond
Metallic Bond
  • Metal ions with an electron sea.
2 8 naming inorganic compounds ionic
2.8 – Naming Inorganic CompoundsIonic

Names and Formulas of Ionic Compounds:

  • Cations
    • One charge only = name only

Zn+2 = Zinc ion

Ca+2 = Calcium ion

    • Multiple charges possible = use Roman Numeral

Cu+1 = Copper (I)

Cu+2 = Copper (II)

-Old system uses –ous / -ic

    • Polyatomics – hydronium, ammonium
2 8 inorganic compounds ionic
2.8 – Inorganic CompoundsIonic

Names and Formulas of Ionic Compounds:

2. Anions:

  • Monotomic – Change ending to –ide
  • Polyatomic – MEMORIZE 8-ates and rules!
  • H+ added ions = use bi- or hydro-prefix

Example – bicarbonate = hydrogen carbonate

  • Carbonate CO3-2
  • Nitrate NO3-1
  • Sulfate SO4-2
  • Chlorate ClO3-1
  • Chromate CrO4-2
  • Bromate BrO3-1
  • Phosphate PO4-3
  • Iodate IO3-1
2 8 inorganic compounds ionic1
2.8 – Inorganic CompoundsIonic

Ionic Compounds – Cation + Anion

-Binary – Compound of 2 “atoms”

-ex – NaCl, Al2O3

-Ternary – Compound of 3 “atoms”

-ex – Mg(NO3)2

2 8 inorganic compounds binary molecular
2.8 – Inorganic CompoundsBinary Molecular

Molecular Compounds: Discrete molecular units. Contain covalent bonds. Use prefixes.