1. ATOMS Chapter 4

2. What is an Atom? • The smallest particle into which an element can be divided and still be the same substance • The building blocks of all matter

3. Size of Atoms • Atoms are really, really small • Even the biggest atoms can’t be seen

4. Can you cut it? • Cut a strip of paper 28 cm long by 4 cm wide • If you can cut the strip of paper in half 31 times you will end up with a piece of paper the size of an atom. • Take your strip of paper and cut it into equal halves. • Cut one of the remaining pieces of paper into equal halves. • Continue to cut the strip into equal halves as many times as you can. • Make all cuts parallel to the first one. When the width gets longer than the length, you may cut off the excess, but that does not count as a cut.

5. How far did you get? • Here are some comparisons to think about! • Cut 1 14.0cm Child's hand • Cut 2 7.0 cm Fingers, ears, toes • Cut 3 3.5 cm Watch, mushroom, eye • Cut 4 1.75 cm Rings, insects • Cut 6 .44 cm Poppy seeds • Cut 8 1 mm Thread. Congratulations if your still in! • Cut 10 .25 mm Still cutting? Most have quit by now • Cut 12 .06 mm Microscopic range, human hair • Cut 14 .015 mm Width of paper, microchip components • Cut 18 1 micron Water purification openings, bacteria • Cut 19 .5 micron Visible light waves • Cut 24 .015 micron Electron microscope range • Cut 31 .0001 micron The size of an Atom!

6. Is there anything smaller than an atom? • YES

7. Parts of an Atom • Three subatomic particles (there are more) - protons – positive charge, located in the nucleus - neutrons – no charge, located in the nucleus - electrons – negative charge, located in the electron cloud

10. Charged Atoms • When an atom has the same number of protons and electrons, the atom is neutral • When there is a different number of protons and electrons, the atom has a charge • Charged atoms are called ions

11. An ion is positive when the protons outnumber the electrons • An ion is negative when the electrons outnumber the protons

12. Isotopes • Atoms of an element that have the same number of protons but different number of neutrons

13. Do Section Review Page 89

14. Electron Shells • 1st shell can hold 2 • 2nd shell can hold 8 • 3rd shell can hold 18 but for our purposes we will consider it full at 8

15. Bohr Models

16. Do Bohr Model activity sheet

17. Forces • Gravity – attraction between particles in the atom. Very small force in the atom • Electromagnetic – holds electrons around the nucleus • Strong – holds the nucleus together (is stronger than the electromagnetic force that is pulling it apart • Weak – responsible for radioactivity. Helps change neutrons into protons and electrons