2. CHEMISTRY- Elements, Atoms & Compounds INTRODUCTION TO THE PERIODIC TABLE OF ELEMENTS

3. WHAT IS AN ELEMENT? review Substance made up of a single type of atom. Can’t be broken into simpler components by chemical or physical processes. There are 92 naturally occurring elements. They may be solids, liquids or gases. Have Symbols- O (Oxygen), H (Hydrogen), N (Nitrogen), Mg (Magnesium), C (Carbon), Cl (Chlorine), Na (Sodium)

4. Gold is one example of an element. A bar of gold can be shaved into gold dust, and still be recognizable as gold. A bar of gold can be shaved into gold dust, and still be recognizable as gold. How fine can the dust become and still be considered gold? The smallest particle that would still have the properties associated with gold is an atom. How small is an atom? Consider that a small gold coin may contain over 2.0 X 10 22 atoms.

5. What is an Atom? An atom is the basic structure from which all matter is composed. Although atoms are too small to be seen with our eyes, scientists have long had indirect evidence for the existence of atoms.

6. All atoms have 2 common structures: nucleus energy level(s)

7. energy level nucleus electrons+ + protons neutrons- - Each structure is made of subparticles.

9. History of Elements and Atoms Some elements were discovered as early as Ancient times. (Silver, Sulfur, Gold, Copper etc.)Some elements were discovered as early as Ancient times. (Silver, Sulfur, Gold, Copper etc.) The first idea of atoms was originally proposed by an ancient Greek Philosopher, Demokritos (~ B.C. 500)The first idea of atoms was originally proposed by an ancient Greek Philosopher, Demokritos (~ B.C. 500) The first new scientific discovery of an element occurred in 1669 when Hennig Brand discovered phosphorous.The first new scientific discovery of an element occurred in 1669 when Hennig Brand discovered phosphorous. Some elements were discovered as early as Ancient times. (Silver, Sulfur, Gold, Copper etc.)Some elements were discovered as early as Ancient times. (Silver, Sulfur, Gold, Copper etc.) The first idea of atoms was originally proposed by an ancient Greek Philosopher, Demokritos (~ B.C. 500)The first idea of atoms was originally proposed by an ancient Greek Philosopher, Demokritos (~ B.C. 500) The first new scientific discovery of an element occurred in 1669 when Hennig Brand discovered phosphorous.The first new scientific discovery of an element occurred in 1669 when Hennig Brand discovered phosphorous.

10. Dmitri Mendeleev Father of the Periodic Table In 1860, at the age of 26, Mendeleev was working on a writing a chemistry book. He noticed patterns and trends among the elements. He ordered elements according to increasing atomic masses. He then placed the elements into a table called the periodic table of the elements, his greatest achievement. By 1869 when his book was published, 63 elements had been discovered.

12. H.G.J. Moseley (Thomas) Used X-Rays to measure the protons in nearly all of the elements Determined that the elements should be ordered based on atomic number versus atomic mass Died at the age of 28 in war Used X-Rays to measure the protons in nearly all of the elements Determined that the elements should be ordered based on atomic number versus atomic mass Died at the age of 28 in war

15. N 7 nitrogen 14.007 G element symbol atomic number state of matter element name atomic mass How many electrons? How many protons? How many neutrons? 7 7 7 An example of an entry in the periodic table.

16. The number of protons in the nucleus of an atom is that atom’s atomic number. Gold has 79 protons. The atomic number of gold is ___. Carbon has 6 protons. The atomic number of carbon is 6. + - - - - - - + + + + + The number of protons plus the number of neutrons in the nucleus of an atom is its atomic mass.

17. N 7 nitrogen 14.007 G The atomic mass is always rounded to the nearest whole number 14.007 to 14 26.560 to 27

18. To find the number of neutrons in an atom, subtract the atomic number from the atomic mass. 16 Atomic mass (protons + neutrons) - 8Atomic number (protons) ___ 8Number of neutrons

19. Atomic Number = Atomic Mass = Protons = Neutrons = Electrons = Energy Levels = 8 16 8 8 8 2 oxygen atom