The Periodic Table (6.1)

Elements At the present time 114 elements are known. These elements vary widely in their abundance For example, only five elements account for over 90% of the Earth's crust: oxygen, silicon, aluminum, iron, and calcium. In contrast, just three elements (oxygen, carbon, and hydrogen) account for over 90% of the mass of the human body.

Elements The Periodic Table pure substances that cannot be broken down into a simpler chemical substance by any physical or chemical means

Symbols for Elements Symbols consist of one or two letters. The first letter is always UPPERCASE. If there is a second letter, it is always lowercase. H He Ca Hydrogen Helium Calcium

Compounds a pure substance composed of two or more different elements that are chemically joined

H2O Symbols for Compounds Symbol for the element hydrogen Symbol for the element oxygen H2O The small number (subscript) after the element tells us the number of atoms of that element. (There are 2 atoms of hydrogen in this compound) If there is no small number (no subscript) after the element, there is only 1 atom of that element. (There is 1 atom of oxygen in this compound)

Families used to describe columns in the table Column   

Metals, Non-metals, Metalloids **draw a staircase onto your own copy of the periodic table

everything to the left of the staircase is a metal everything to the right of the staircase is a non-metal Elements located along the staircase line (except Al) are called metalloids because they have properties of both metals and non-metals.

Properties of Non-Metals Properties of Metals shiny good conductors of heat and electricity Usually solid (except mercury – liquid) Malleable ductile Properties of Non-Metals dull poor conductors of heat and electricity Solids, liquids, or gases brittle

State of Element at Room Temperature Solids: most of the elements on the table occur in this state at room temperature Liquids: only mercury (Hg) and bromine (Br) can be found as liquids at room temperature Gases: many of the non-metals and hydrogen (H)

Reactivity The alkali metals are the most reactive metals (Francium is the most reactive) The most reactive non-metals are the halogens (Fluorine is the most reactive) The noble gases are stable and do not react with anything

Alkali Metals

Periodic Table Video Homework: p. 215 #1-10 http://www.periodicvideos.com/# Homework: p. 215 #1-10