1. Atoms, Molecules, and Ions
Atomic Theory of Matter
John Dalton – earliest version of the atomic theory
Elements are composed of small particles called atoms.
2. Atoms of a given element are identical
Law of Conservation of Matter/Energy – matter/energy cannot be created or destroyed
4. Two or more elements that combine chemically form compounds

2. Atomic Theory of Matter
Element – one kind of atom
Compound – 2 or more elements chemically bonded. Chemically different than elements
Mixture – 2 or more substances together, each maintains its chemical identity

3. Discovery of Atomic Structure
Similar charges repel each other
Opposite charges attract each other
Radioactivity
Ernest Rutherford – 3 types of radiation
Alpha (α) – positively charged particle
Beta (β) – negatively charged particle
Gamma (γ) – no charge; dangerous
Alpha particle (α) is the core of a helium atom

4. Nuclear Atom
J.J. Thomson – atoms are a uniform positive sphere with electrons embedded in it.
“Plum Pudding Model”

5. Nuclear Atom
Rutherford – fired alpha particles at gold foil to study scattering, most went straight through, some bounced straight back.

6. Rutherford – the Nuclear Atom
Deduced that:
most of an atom is empty space
center of atom has a positive charge
The nucleus – small and dense
contains the majority of the mass of an atom
Rutherford Gold Foil Animation

7. 2.3 Modern View of Atomic Structure
Atoms are composed of 3 particles
Proton – positive charge (+)
Neutron – neutral charge
Electron – negative charge (-)
Mass of an atom – all in nucleus sum of protons and neutrons

8. Modern Atomic Structure
Size of an Atom – Between 1-5 Angstroms (Ǻ)
Angstrom (Ǻ) = 1 x m
Electron Cloud – area around nucleus where electrons spend most of their time
- makes up most of the size of an atom
- mostly empty space

9. How many copper atoms (DCu atom = 2
How many copper atoms (DCu atom = 2.6 Ǻ) fit across the edge of a penny (19 mm)?

10. Isotopes, Atomic #, Mass #
Isotopes, atomic #, and mass # - bookkeeping of subatomic particles
All atoms of an element have the same number of protons
Isotopes – Atoms of the same element with differing #’s of neutrons
- affects mass #

11. Atomic Number (Z) – number of protons
Mass Number (A) – # of protons + neutrons
Examples:

12. 2.4 Periodic Table (developed in 1869)
Your new best friend!!!!
Periodicity – repeating patterns of chemical and physical properties
Vertical Columns – family or group; similar chemical behavior
Horizontal Rows – Periods

14. Metals – Left of staircase; except Hydrogen;
Metals – Left of staircase; except Hydrogen; most are _________ at room temp.
Nonmetals – Right of staircase; includes H
most are _______ at room temp.
Metalloids – lie along staircase,behave as metal and nonmetal
Elements Song
Meet the Elements

16. 2.5 Molecules and Ions
Molecule – Two or more nonmetal atoms bonded together
7 Diatomic molecules: Horses Need Oats For Clear Brown Irises H2 N2 O2 F2
Cl2
Br2 I2

17. 7 Diatomic Molecules

18. Subscripts – represent the # of atoms of the element just before it
Ex: H2O C6H12O6
CaSO4 Mg3(PO4)2

19. Molecular, Empirical, and Structural Formulas
Molecular Formula – Actual # of atoms
Example: C6H12O6 , H2O2
Empirical Formula – Relative # of atoms
smallest whole # ratio
usually for ionic compounds
Example: CH2O , HO , NaCl

20. Formula Types (con’t) Structural Formula – lines represent bonds;
indicates which atoms are bonded to each other

21. Ions – form when an atom gains or loses electrons
Cation – metal atom loses electrons to form a positive ion
Anion – nonmetal atom gains electrons to form a negative ion
Metals are losers (shhhhhh!)

22. Symbol
17O2-
52Cr3+
Protons 38 34
Neutrons 50 45 74
Electrons 36 54
Net Charge 2+ 1-

23. Polyatomic Ions Polyatomic Ions – many atoms with a charge
See test packet for a list of common PAI’s
Covalently bonded (nonmetals)

24. Predicting Ionic Charge
Predicting Ionic Charge - use the staircase
metals – lose electrons, form cations
nonmetals – gain electrons; form anions
Atoms will gain or lose electrons to have the same number of electrons as the nearest noble gas (for the main group [A] elements only)
NOBILITY IS STABILITY

25. Ionic vs. Covalent
Ionic Compounds – electrons are transferred from the metal (loser) to the nonmetal
Empirical formula shows ratio – ionic compounds form large 3-D crystals.
Covalent molecule – electrons are shared between 2 or more nonmetals