Bell Ringer 9-28-09 What two other things does the atomic number tell you? Where can the atomic number be found in the element square? Where can the atomic mass be found in the element square? Atomic mass rounded is called __________. How do we find the number of neutrons in an atom?

Objectives ALCOS # 2 Describe the structure of atoms. ALCOS # 3 Determine the # of protons, neutrons, and electrons of atoms.

Chapter 4 Section 2 Organizing the Elements

Mendeleev In 1869, he created the first periodic table. He noticed a pattern in the elements when he arranged them in order of increasing atomic mass.

Henry Moseley Rearranged the Periodic Table in order of increasing atomic number instead of mass

Periodic Table’s Organization The properties of an element can be predicted from its location in the periodic table. Today, the periodic table is arranged in order of increasing atomic number.

Organization of the Periodic Table Periods- the horizontal rows (sideways) There are 7 periods. Groups (Families)- the vertical columns (up-and-down) There are 18 groups.

Element Square 1 H Hydrogen 1.0079

Elements 1-92  Found in nature All elements above 92  synthetic (man-made)

Elements in the Human Body Oxygen (65%) Carbon (18%) Hydrogen (10%) Nitrogen (3%) Calcium (1.5%) Phosphorus (1.0%) Potassium (0.35%) Sulfur (0.25%) Sodium (0.15%) Magnesium (0.05%) Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron (0.70%) Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium, Arsenic, Bromine (trace amounts)

Sun The sun is mostly made of Hydrogen. It exists at very high temperatures (15 million degrees Celsius). At these high temps, matter cannot exist as a solid, liquid, or gas, so it is plasma.

Stars Nuclear Fusion- when 2 atomic nuclei combine, forming a larger nucleus (releases a lot of energy) Happens in stars

Stars Nuclear Fusion

Interactive Websites Periodic Table of the Elements The Periodic Table of the Elements, Standard Form