 Each element on the Periodic Table has a unique atomic structure
 Each element has a symbol that is used as a shorthand way to identify the element
– If the symbol has more than one letter, only the first letter is capitalized, if it only has one letter it should be capitalized
– Examples:
• Helium = He
• Nitrogen = N

 The period an element is in tells you how many energy levels an atom of a particular element has
 Period # = # of energy levels
– For example, elements in period 4 each have a total of 4 energy levels for electrons

 Mass increases as you move from left to right and as you move down the
Periodic Table
 Atomic number also increases as you move from left to right and as you move down the Periodic Table

 Elements on the left of the Periodic
Table are more metallic than those on the right
 Elements are less metallic as you move to the right of the Periodic Table
 Metals are shiny, hard, malleable, ductile, high density, good thermal and electric conductors

 Valence electrons are electrons in the outermost level of an atom, furthest from the nucleus
 The number of valence electrons in an atom increases from left to right within a period

 Groups 1 & 2:
– # of valence electrons = group #
 Groups 3-12:
– # of valence electrons = 1 or 2
(no specific rule for these elements)
 Groups 13-18:
– # of valence electrons=group # - 10
– For example: group 15 has 5 valence electrons

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The number of valence electrons determines the reactivity of an element
The reactivity of an element determines how well it will combine with other elements to form new substances
Metals - become less reactive as you move from left to right
Nonmetals - become more reactive as you move from left to right, except for Noble Gases
Noble Gases only react with other elements in a lab setting

 Elements want to have a full outer energy level, which is either 2 or 8 electrons
 Alkali Metals have 1 valence electron, so they are the most reactive metals
 Halogens are the most reactive nonmetals
 Noble Gases have 8 valence electrons, so they are the least reactive elements