1. Review Scientist who discovered the electron using the cathode ray tube –Thomson Scientist who used the oil drop experiment to discover the charge on the electron –Millikan Scientist who conducted the gold foil experiment to discover that the nucleus is small, dense, and positively charged. –Rutherford

2. Review Scientist that developed the pulsating planetary model –Bohr Scientist that discovered the existence of the neutron –Chadwick Scientist that had the solid sphere model of the atom –Dalton

3. Review Greek philosopher who coined the term atom from the Greek word atomos –Democritus Greek philosopher who did not believe in the atom –Aristotle Scientist who created the law of definite proportions –Proust

4. Review Scientist who created the law of multiple proportions –Dalton Scientist who created the law of conservation of mass –Lavoisier

5. Review

6. An atom is the smallest particle of an element that gives it its chemical and physical properties.An atom is the smallest particle of an element that gives it its chemical and physical properties. The atom is extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. The atom is extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. If a large sports stadium were an atom, a marble would represent the nucleus. If a large sports stadium were an atom, a marble would represent the nucleus.

7. An atom consists of a Positively charged nucleus that contains protons and neutronsPositively charged nucleus that contains protons and neutrons Negatively charged electrons in space outside of the nucleus.Negatively charged electrons in space outside of the nucleus. Atom Structure Nucleus Electron cloud

8. Atoms found in nature have a neutral charge. Why?

9. Atomic Number All atoms of the same element have the same number of protons in the nucleus 13 Al 26.981 Atomic number Atom symbol AVERAGE Atomic Mass

10. Atomic Number Atomic # = # protons = # electrons *only for neutral atoms

11. Mass Number Mass NumberMass Number = # protons + # neutrons NOT on the periodic table, electron is so small that its mass is negligibleNOT on the periodic table, electron is so small that its mass is negligible

12. Average Atomic Mass Weighted average, more abundant isotopes have a greater affect –On the periodic table

13. Atomic Symbols Hyphen/mass notation - show the name of the element, a hyphen, and the mass number in sodium-23 Nuclear symbol - show the mass number and atomic number next to the chemical symbol mass number 23 Na atomic number 11

14. Figure 3.10: Two isotopes of sodium.

15. Isotopes Atoms of the same element but different mass number.Atoms of the same element but different mass number. Boron-10 ( 10 B) has 5 p and 5 nBoron-10 ( 10 B) has 5 p and 5 n Boron-11 ( 11 B) has 5 p and 6 nBoron-11 ( 11 B) has 5 p and 6 n 10 B 11 B

16. Practice Ar-40 P-31

17. Isotopes? Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 9292

18. 1.An __ ___ is the smallest particle of an element that has the chemical properties of the element. 2. The 3 particles that make up the atom are ________, _________, and _________. 3. Atoms with the same number of protons and electrons, but a different number of neutrons are called ____________. 3. Atoms with the same number of protons and electrons, but a different number of neutrons are called ____________. 4. ___________ was an English scientist who developed an atomic theory in the early 1800s.