Periodic Table
Vocabulary
2012-13
Periodic Trend
a predictable pattern
of gradual change of
certain properties of
elements to increase
or decrease as one
progresses across a
row or down a
column
groups/families
vertical columns
on the periodic
table
have similar
properties; “like
brothers and
sisters”
18 groups
Periods
Horizontal rows on
periodic table
properties change
gradually, but predictably
as you go across the row
“like cousins”
7 periods
Atomic number
the number of
protons in the
nucleus of an
atom
Valence Electrons
the electrons on the
outermost energy level
(shell, orbital)
determines reactivity
the closer to a full shell,
the less reactive
Reactivity
the tendency for an
element or
substance to
undergo a
chemical reaction,
either by itself or
with another
substance
Metals
elements that:
✴
have luster
✴
are good conductors of heat
and electricity
✴
are malleable (can be flattened
into sheets)
✴
are ductile (can be stretched
into wires)
found on the left side of the
“staircase” on the periodic table
Nonmetals
elements that:
✴
are usually gases or brittle
solids
✴
are poor conductors of
heat and electricity
found on the right side of the
“staircase” on the periodic
table
Metalloids
elements that:
✴
have different properties of
both metals and nonmetals
Often semiconductors
sometimes called
“semimetals”
found touching the “staircase”
on the periodic table