Blue Physical Science Book pp 336 - 342 The Periodic Table Blue Physical Science Book pp 336 - 342

I. Discovering a Pattern 1. Dimitri Mendeleev is credited with 'discovering' the periodic table. He figured out patterns in elements' physical properties

a. Periodic Properties of the elements 1. "periodic" means repeating at regular intervals (for example, there are 7 days/week) 2. Mendeleev's table repeated when he arranged the elements in order of increasing atomic size. (3.) Mendeleev's table is called the "Periodic Table of the Elements"

b. Predicting Properties of Missing Elements 1. Mendeleev noticed that the elements fit the pattern if he left gaps in the series. 2. He predicted the properties of the missing elements and he was right!

II. Changing the Arrangement 1. Moseley (a British scientist) noticed that if you arranged the elements by their number of protons, the few elements in Mendeleev's table that didn't fit worked out better. 3. "Periodic Law" = repeating chemical and physical properties of elements change with the elements' atomic number (# of protons)

III. The Periodic Table and Classes of Elements 1. The zigzag line on the periodic table separates the metals and nonmetals

a. Metals 1. Most elements are metals 2. Most metals are solid at room temperature. (Mercury is liquid.) 3. Metals are good conductors of heat and electricity. 4. They tend to be shiny, ductile, malleable

b. Nonmetals 1. Nonmetals have an almost complete set of electrons. 2. Nonmetals are mostly gases at room temperature. 3. Nonmetals are poor conductors of heat and electricity. 4. Nonmetals are not malleable or ductile. (They are brittle).

c. Metalloids 1. Metalloids are also called semiconductors. 2. They border the zigzag line on the periodic table. 3. The have some properties of metals and some properties of nonmetals. 4. Metalloids have about half of a complete set of electrons (which means they tend to be less reactive).

IV. Decoding the Periodic Table 1. The periodic table is like a code.

a. Each element is Identified by a Chemical Symbol 1. Elements can be named for scientists or places. 2. Elements have the same symbol in every country. 3. The first letter is always capitalized, the second letter is always lower case.

b. Rows are called Periods 1. Periods are horizontal rows 2. Properties change gradually from left to right as you move across a period.

c. Columns are Called Groups 1. Vertical columns are called groups or families. 2. Elements in a group/family have similar properties.

Atomic Number = Number of Protons Atomic Mass = Protons + Neutrons

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