Elements and the Periodic Table

Vocabulary Mendeleev – said elements are periodic Periodic Law – elements have a regular repeating pattern based on their atomic # Atomic # – # of protons Valence electrons – electrons in the outermost electron shell (valence shell)

The Periodic Table Arranged in increasing atomic # Period – horizontal rows Groups – vertical columns; in each group, elements have some similar properties

The Periodic Table of Elements Metals Metalloids Nonmetals

Metals Most elements are metals Found to the left of the periodic table Most have few electrons in their outermost energy level Most are solid at room temperature Good conductors (allow heat and electricity to pass through) Shiny Malleable (can be flattened without shattering). Ductile (can be drawn into wires).

Nonmetals Found to the right of the periodic table. Poor conductors Have almost complete valence energy levels. More than half are gases at room temperature. Have opposite properties of metals. Poor conductors Dull Brittle & break easy. They are not malleable or ductile because they break easy.

Metalloids They are the elements that border the zigzag line on the periodic table (except aluminum). They have about a half complete valence or outer energy level. They have some properties of metals and some properties of nonmetals. Example: Tellurium is shiny but it is brittle.

Periods tell how many energy levels an element has

Groups tell how many valence electrons an element has

Group 1 – The Alkali Metals Very Reactive!!! 1 electron in valence shell all metals Soft, silver-colored, shiny, low density Li, Na, K, Rb, Cs, Fr

Group 18 – Noble (Inert) Gases Unreactive!!! They are stable! 8 electrons in the valence shell (2 for Helium) Colorless, odorless gases at room temp. He, Ne, Ar, Kr, Xe, Rn Everyone wants to be like them!

Hydrogen stands alone!!!!!! Hydrogen is reactive!!!!!!!!!!!!! Has 1 electron in its outer shell Colorless, odorless gas at room temperature Reacts explosively with oxygen