1. The Atom Created by Dr. A. Davila

9. Atoms and Their Electrons. Classroom Media, 1995. Full Video. 30 September 2010..

12. Elements in the Human Body

13. Composition of Air COMPONENTVOLUME Nitrogen78% Oxygen21% Other1%

14. Composition of the Air on Planet Earth

16. Elements in Our Body and Atmosphere

17. The Carbon Cycle

20. Describe an Element Identify the element Provide the elements’ symbols Provide its atomic number and atomic mass What is its appearance, its other properties Explain its uses How would you classify it?

25. periods groups metals metalloidsnonmetals Atomic # always capitalized Never capitalized dissimilar similar malleable electrical conductor brittle Electrical insulator

26. metals nonmetals Shiny luster dull luster conductor insultor malleable high melting point brittle low melting point

27. Democritus disagreed with other philosophers who thought that matter could be explained only by descriptive terms. In his view, all of the descriptions of matter were secondary to the identity of the atoms making it up.

28. Rutherford called the positively charged, central part of the atom the nucleus. He named the positively charged particles in the nucleus protons. He also suggested that electrons were scattered in the mostly empty space around the nucleus. Thee atoms must be made of mostly empty space.

29. Niels Bohr found evidence that electrons in atoms are arranged in energy levels. The lowest energy level is closest to the nucleus and can hold only two electrons. Higher energy levels are farther from the nucleus and can contain more electrons. This simplified model shows a nucleus of protons and neutrons and electron paths based on energy levels.

30. The Modern Atomic Model As a result of continuing research, scientists now realize that because electrons have characteristics that are similar to waves and particles, their energy levels are not defined, planetlike orbits around the nucleus. Rather, it seems most likely that electrons move in what is called the atom's electron cloud.

31. Lavoisier showed that wood and the oxygen it combines with during burning have the same mass as the ash, water, carbon dioxide, and other gases that are produced. In a similar way, an iron bar, oxygen, and water have the same mass as the rust that forms when they interact. From Lavoisier's work came the law of conservation of matter, which states that matter is not created or destroyed? Matter only changes form.