1. Atoms

2. Elements vs. Compounds  Elements can NOT be chemically broken down to a simpler substance, compounds can. (Ex. H 2 O  H 2 + O 2 )  Pure substances can be either elements or compounds. Most materials are MIXTURES of pure substances.  There are only 88 naturally occurring elements, 114 elements that are known.

3. Dalton’s Atomic Theory  Elements are made of tiny particles called ATOMS  All atoms of a given element are identical  The atoms of a given element are different from those of any other element

4. Atomic Theory Cont’d  Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms.  Atoms are indivisible in chemical processes. That is, atoms are not created or destroyed in chemical reactions. A chemical reaction simply changes the way atoms are grouped together.

5. Law of Constant Composition  A given compound always contains the same proportions (by mass and by number) of its elements  This means a given compound always has the same composition, regardless of where it came from.

6. Chemical Formulas  A formula describes how a compound is composed in terms of atoms (how many and which) How many of each atom are in:  Na 2 CO 3  (NH 4 ) 3 PO 4

7. ATOMS

8. Subatomic Particles  Protons – (p + )  Defines the element  Is the integer number (Atomic Number) on the periodic table  Have a positive charge  Has a mass of 1 a.m.u.  How many protons does Carbon have?  How many protons does Iron have?  How many protons does Ununnilium have?  What element has 35 protons?

9. Subatomic Particles  Neutrons – (n 0 )  Have no (neutral) charge  Have a mass of ~1 a.m.u.  Contribute to the total mass of an atom  Define the isotope of an atom  How many neutrons does Carbon-12 have?  How many neutrons does Carbon 14 have?  How many neutrons does Uranium-238 have?

10. Subatomic Particles  Electrons – (e - )  Have a negative charge  Equal numbers as protons in NEUTRAL atoms  Gained, lost, or shared in CHEMICAL REACTIONS  Have a mass of 1/1836 th of a proton (neglible!) How many electrons does Carbon have? How many electrons does F - have?

11. Make Up Of Atom  Protons and Neutrons are in the center of the atom.  Electrons are whizzing around on the outside of the atom.  What element (and isotope) is this atom?

12. Empty Space  There is a LOT of empty space is in between the nucleus and the electrons  If the nucleus was a marble on the 50 yard line of a football stadium, the electrons would be in the nosebleed seats…

13. Isotopes  Isotopes are atoms of an element that have different masses.  Same element = same # protons  Different mass = different # neutrons  Isotopes are also known as nuclides  Every element has many nuclides – both stable and unstable  The atomic mass on the periodic table is the weighted average of all the stable nuclides of that element.

14. Isotopes  The specific isotope of any element is written with the generic formula Z A X Where Z = the atomic number A = the mass number (protons + neutrons) X = the elemental symbol  Write the symbol for Magnesium with 13 neutrons.

15. Chart of Nuclides (black = stable, red = unstable)

16. Chemical v. Nuclear Reactions  Chemical reactions:  Electrons are involved (exchanged or shared)  Atoms are rearranged, but stay as the same atom.  What we will be studying most this year  Nuclear reactions:  Nucleii (protons and neutrons) are involved and changed.  Atoms become different elements by losing or gaining protons.