Unit 2 - Chapter 3 Elements, Atoms, Ions

1. Unit 2 - Chapter 3Elements, Atoms, Ions

2. The elements • Can we name some? • How many are there? • Where would you find that information?

3. Element Symbols • Each element has a unique symbol. • The first letter is always capitalized • if a second letter, it is always lower case • Usually the 1st letter of its name, then the 2nd letter or unique letter. • Carbon, Calcium, Cadmium, Californium • Some unusual symbols - mostly based on latin roots • sodium, potassium, gold, lead, mercury, iron, etc.

4. Atomic size • We can take a chunk of matter and break in apart into smaller and smaller pieces, eventually we would get down to individual atoms. Each piece would behave like the original chunk with all of its properties. • The atom is the smallest particle of an element that retains the properties of the element. • 108 copper atoms lined up would be 1 cm. What would be the diameter of a single copper atom?

5. Atomic theory • Democritus (ancient greek philosopher) stated that if you broke down matter eventually you would get to the smallest particle of matter that could not be divided (atomos) • John Dalton - 1800s - Did Chemical Experiments! • Things (matter, compounds) always combined in the same proportions SIMPLE WHOLE NUMBER RATIOS • Law of Constant Composition - a compound always has the same composition regardless of where it comes from or how it is made • Dalton’s Atomic Theory - page 56 of textbook

6. Dalton’s Atomic Theory • Elements are made of tiny particles - atoms • All atoms of an element are identical. • Atoms of an element are different from all other elements. • Atoms can combined to form compounds. A compound always has the same number and types of atoms. SIMPLE WHOLE NUMBER RATIOS • Atoms are not created nor destroyed by chemical reactions, simply rearranged or grouped together differently

7. Compounds • Compound is a distinct substance, that is composed of 2 or more elements, always in the same proportions (whole number ratios) • Can we name some? • A compound has a unique chemical formula, which indicates which elements and how many are in that particular substance.

8. Atomic Structure • What is a Model of the atom? • How did we get there? • Dalton - Chemical Experiments determined atom was indivisible (a solid sphere) • Cathode Ray tube experiments by J.J. Thomson (plum pudding model or TODAY maybe chocolate chip ice cream) • Gold foil experiment by E. Rutherford (nuclear atom - the marble in the Metrodome)

9. J.J. Thomson’s Experiment • The cathode ray tube discovered was a beam of particles • The beam was deflected by magnets • changed the gas -> didn’t change beam, • changed metal anode -> didn’t change beam • Particle was a fundamental particle of all substances! • Particle was a part of all atoms!!!! 1st Subatomic particle, so the atom was made of smaller particles • JJ Thomsom discovered the electron. Didn’t know about the rest of the atom, so just said it was like Plum Pudding

10. Rutherford’s Gold foil Experiment • Bombarded a thin gold foil with positively charged alpha particles. Looked at flashes of light when film was hit. • Most of the particles went straight through • 1 out of 20,000 bounced almost directly back • Conclusions: • Atom is mostly empty space • positively charged nucleus with most of the mass

12. Extra Credit - Unit 2 • Chapter 3 - pg. 86-88 , # 5, 6, 7, 10, 12, 14, 17, 18, 19, 21, 23, 29, 30, 33, 35, 39, 40, 41, 42, 46, 53, 55