The Periodic Table

Basics 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

Periods and Energy Levels 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 and Atomic Number 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

Metallic Properties 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 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

Determining Number of Valence Electrons 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

Reactivity 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

Reactivity 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