Unit 1 B.6, B.7, B.8, B.9

Elements on the periodic table are grouped according to their similar properties.  Horizontal rows on the periodic table are called periods and columns are called groups or families.  The alkali metal family consists of six elements: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).  These elements are all highly reactive metals that form a chloride compound with a 1:1 alkali metal atom to chlorine atom ratio and an oxide with a 2:1 alkali metal atom to oxygen atom ratio.  Another family is the noble gas family.  The gases in this group are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).  These gases are known to be very unreactive.  In the column to the left of the noble gases is the halogen family, a group containing fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).  When elements in the halogen group form compounds, they are known as halide compounds.  The halogen gases are highly reactive and readily form binary compounds with hydrogen.  The arrangement of the periodic table is useful because it groups elements according to their key characteristics.  It can help scientists determine properties of any element in a chemical family because of the other related elements.  An element’s properties can be determined by averaging the properties of the elements directly and directly below it.  Chemical formulas can also be predicted in the same manner.