Classifying Elements
Newland's
Octaves
Li, Be, B, C, N, O, F, Na, Mg, Al, Si,
P, S, Cl, K, Ca
( #8 is similar to #1)
( #9 is similar to #2)
Mendeleev's Period Law 1869
Periodic Law: Placed elements in
horizontal rows by atomic mass
and in columns by chemical
properties.
Problem: atomic mass doesn’t
increase regularly.
Modern Periodic Law and the
Periodic Table
The properties of elements
repeat periodically when the
elements are arranged in
increasing orders by their
atomic number.
Groups or Chemical Families
these are the vertical columns of
the periodic table
group # is indicated at the top of
the group
the
main group elements have
the same number of valence
electrons
all
elements of a chemical
family have the same
fundamental chemical
properties
differences between the
elements within a group differ
primarily due to their size
differences
Periods
these are the horizontal
rows of the periodic table
the period # is indicated at
the left of the row
the period # also indicated the
principle energy level (the level
where valence electrons are
being filled)
differences between elements
in a period are primarily due to
differences in nuclear charge
Metals
 The left 2/3 of the period
table (left of the staircase)
are METALS.
– As you proceed left in a
period, or down in a group,
the metallic properties of an
element will INCREASE.
The most metallic element
on the periodic table is
Fr--FRANCIUM.
Properties of Metals





shiny or lustrous
malleable - can be hammered
into shapes
ductile - can be stretched (i.e.
can be stretched into wires)
good conductor of electricity
high melting and high boiling
points
Nonmetals
 The right 1/3 of the periodic
table (right of the staircase)
are NONMETALS.
– As you proceed right in a
period or up in a group, the
nonmetallic properties of
an element will INCREASE.
The most nonmetallic
element on the periodic
table is F—FLUORINE




Properties of Nonmetals
hard
brittle
poor conductors of
electricity
low melting and low
boiling points
Metalloids

The elements on the
staircase are called
METALLOIDS
– These have properties of
both metals and
nonmetals
They include B, Si, As, Te,
At, Ge, Sb
(Boron, Silicon, Arsenic,
Tellurium, Astatine,
Germanium, Antimony and
Polonium)
exception: Aluminum and
Polonium
How to Determine Phases
 If
the melting and boiling points
are both below 273K it will be a
gas.
 If the melting point is below
273K but the boiling point is
above 273K it will be a liquid.
 If the melting and boiling points
are both above 273K it will be a
solid.
 See
examples
Electron Configurations
Group
1 – the Alkali Metals
–each element has one
valence electron in its
outermost orbital
–Very reactive, not found in
nature as elements
–All lose 1 electron to form a
+1 ion (cation)
Group
2 – The Alkaline Earth
Metals
–each has two valence
electrons in its outermost
orbital
–less reactive than group 1,
but still not found free in
nature as elements
–all lose 2 electrons to form a
+2 ion (cation)
Group
17 – The Halogens
–each has seven valence
electrons
–each gain 1 electron to form
a -1 ion (anion)
Group
18 – The Noble Gases
–All noble gases have the
stable octet noble gas
configuration ( 8 valence
electrons) , except He, and
therefore do not gain or
lose electrons.
Groups
3 – 11 Transition
Metals
–form colored ions in
solutions
–used in tools, wire, jewelry
and coins
Inner Transition Metal
the lanthanoid and actinoid
series
All other groups will be
named for the first element in
that group (Carbon group,
Nitrogen group)
Atoms vs Ions
 Goal:
all elements are seeking a
noble gas configuration
 Metals are atoms that LOSE electrons
to form a POSITIVE ion.
– POSITIVE ions are SMALLER than their
neutral atoms.
 Nonmetals
are atoms that GAIN
electrons to form a NEGATIVE ion.
– NEGATIVE ions are LARGER than their
neutral atoms.
Factors that Determine Periodic Trends



Nuclear charge (period)- Increased #
protons, increased attraction for
electrons
Atomic size (group)- The further
away the electrons are from the
nucleus, the less they are attracted
to it.
Shielding (group)-The core electrons
shield the valence electrons from the
positive charge of the nucleus.
Covalent Atomic Radius


Table S
Half the distance between two
nuclei in a solid crystal
– Trend from left to right (within a
period) = DECREASES
– Trend from top to bottom (within
a group) = INCREASES
Ionic Radius




No table, estimate using Table S
An atom that has gained or lost
electrons will change in atomic size
Metals tend to lose electrons so the
ionic radius will be smaller than the
covalent atomic radius.
Nonmetals tend to gain electrons so
the ionic radius will be larger than
the covalent atomic radius.
Ionization Energy
 Table
S
 The amount of energy required to
remove the most loosely held
valence electrons from a neutral
atom in the gaseous state.
 Trend from left to right (within a
period) = INCREASES
 Trend from top to bottom (within a
group) = DECREASES
Electronegativity
 Table
S
 The measure of attraction an atom
has for a pair of electrons
 Trend from left to right (within a
period) = INCREASES
 Trend from top to bottom (within a
group) = DECREASES
Reactivity




The transfer (gain or lose) of
electrons
Metals are more active toward the
bottom left corner where electrons
are mostly easily lost.
Nonmetals are more active toward
the upper right corner where
electrons are most easily gained.
Noble gases have no (or minimal)
reactivity and this is why they
weren't discovered for many years.
Within a Period, as the Atomic
Number Increases
 covalent
atomic radius
 ionization energy
 electronegativity
 metallic character
DECREASES
INCREASES
INCREASES
DECREASES
Within a Group, as the Atomic
Number Increases
 covalent
atomic radius
 ionization energy
 electronegativity
 metallic character
 Packet
Questions
INCREASES
DECREASES
DECREASES
INCREASES