Transcript Trends of the Periodic Table

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

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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
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