The Periodic Table
and Periodic Trends
Mr. Matthew Totaro
Legacy High School
Honors Chemistry
Dmitri Mendeleev
• Ordered elements by atomic mass.
• Saw a repeating pattern of
properties.
• Periodic law —When the elements
are arranged in order of increasing
relative mass, certain sets of
properties recur periodically.
• Used pattern to predict properties
of undiscovered elements.
• Where atomic mass order did not fit
other properties, he reordered by
other properties.
 Te & I
Mendeleev’s Periodic Table
Mendeleev's Predictions
Tro: Chemistry: A Molecular Approach, 2/e
Periodicity
When one looks at the chemical
properties of elements, one notices a
repeating pattern of reactivities.
Periodic = repeating
Periodicity
= Metal
= Metalloid
= Nonmetal
Metals
• Solids at room temperature, except Hg.
• Reflective surface = Luster.
 Shiny
• Conduct heat.
• Conduct electricity.
• Malleable.
Can be shaped.
• Ductile.
 Drawn or pulled into wires.
• About 75% of the elements are metals.
• Lower left on the table.
Nonmetals
• Found in all 3 states.
• Poor conductors of heat.
• Poor conductors of
electricity.
• Solids are brittle.
• Upper right on the table.
Except H.
Metalloids
• Show some
properties of
metals and some of
nonmetals.
• Also known as
semiconductors.
Properties of Silicon:
Shiny
Conducts electricity
Does not conduct heat well
Brittle
The Modern Periodic Table
• Developed the first modern
periodic table.
• Arranged elements by
increasing atomic number
• Killed in WW I at age 28
(Battle of Gallipoli in
Turkey)
Henry Moseley
The Modern Periodic Table
• Elements are arranged from left to right in
order of increasing atomic number
• There are 18 vertical columns called Families
• There are 7 horizontal rows called Periods.
Tro: Chemistry: A Molecular Approach, 2/e
Buy this as a
The Modern Periodic Table
• Main group = representative elements = “A”
groups
• Transition elements = “B” groups
all metals
• Bottom rows = inner transition elements =
rare earth elements
metals
really belong in Period 6 & 7
Tro: Chemistry: A Molecular Approach, 2/e
Tro: Chemistry: A Molecular Approach, 2/e
= Alkali metals
= Halogens
= Alkali earth metals
= Lanthanides
= Noble gases
= Actinides
= Transition metals
Tro: Chemistry: A Molecular Approach, 2/e
Important Groups - Hydrogen
• Nonmetal
• Colorless, diatomic
gas
 very low melting point
and density
Excited Hydrogen Gas
Tro: Chemistry: A Molecular Approach, 2/e
Important Groups – Alkali Metals
• Group IA = Alkali
Metals
• Hydrogen usually placed
here, though it doesn’t
really belong
• Soft, low melting points,
low density
• Flame tests ® Li = red,
Na = yellow, K = violet
• Very reactive, never find
uncombined in nature
Tro: Chemistry: A Molecular Approach, 2/e
lithium
sodium
potassium
rubidium
cesium
Important Groups - Alkali Earth Metals
• Group IIA = Alkali Earth
Metals
beryllium
• harder, higher melting, and
denser than alkali metals
magnesium
Mg alloys used as
structural materials
calcium
• flame tests ® Ca = red, Sr
= red, Ba = yellow-green strontium
• reactive, but less than
corresponding alkali metal barium
Important Groups – Halogens
• Group VIIA =
halogens
• Nonmetals
• Only family with
solids, liquids, and
gases
• All diatomic
• Very reactive
Tro: Chemistry: A Molecular Approach, 2/e
fluorine
chlorine
bromine
iodine
astatine
Important Groups - Noble Gases
• Group VIIIA = Noble
Gases
• all gases at room temperature
 very low melting and boiling
points
• very unreactive, practically
inert
• very hard to remove electron
from or give an electron to
helium
neon
argon
krypton
xenon
Valence Electrons
• The electrons in the highest energy level
are the valence electrons.
• Electrons in the lower energy levels are
called core electrons.
• Chemists have observed that one of the
most important factors in the way an atom
behaves, both chemically and physically, is
the number of valence electrons.
Valence Electrons, Continued
Rb = 37 electrons = 1s22s22p63s23p64s23d104p65s1
• The highest principal energy shell of Rb that
contains electrons is the 5th, therefore, Rb has 1
valence electron and 36 core electrons.
Kr = 36 electrons = 1s22s22p63s23p64s23d104p6
• The highest principal energy shell of Kr that
contains electrons is the 4th, therefore, Kr has 8
valence electrons and 28 core electrons.
Practice—Determine the Number of
Valence Electrons in an Arsenic, As,
Atom (use the Noble Gas shortcut).
Practice—Determine the Number of Valence
Electrons in an As Atom, Continued.
As
Z = 33, therefore 33 e−.
1s
2 e−
+2 = 4e−
2s
2p
3s
3p
3d
+6 +2 = 12e−
4s
4p
4d
4f
+6 + 2 = 20e−
5s +10 + 6 = 36e−
The highest occupied principal energy level is the 4th.
The valence electrons are 4s and 4p and there are 5 total.
Therefore, the electron configuration is 1s22s22p63s23p64s23d104p3.
s1
1
2
3
4
5
6
7
Sublevels and the Periodic Table
s2
p 1 p 2 p 3 p 4 p 5 s2
p6
d1 d2 d3 d4 d5 d6 d7 d8 d9 d10
f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14
Electron Configuration and
the Periodic Table
• Elements in the same column have similar
chemical and physical properties because
they have the same number of valence
electrons.
• The number of valence electrons for the
main group elements is the same as the
group number.
Electron
Configuration of
The Alkali Metals
Electron
Configuration of
The Noble Gases
Electron
Configuration of
The Halogens
31
Periodic Trends in the
Properties of the
Elements
Reactivity
• For the metals, as you move down a family,
reactivity goes up. As you move across a
period, reactivity goes down.
Brainiac’s Video
• For the nonmetals, as you move down a
family, reactivity goes down. As you move
across a period, reactivity goes up.
Except for the Noble Gases!!!!
Trends in Atomic Size
• Either volume or radius.
 Treat atom as a hard marble.
• As you move down a column on the periodic table,
the size of the atom increases.
 Valence shell farther from nucleus.
 Effective nuclear charge fairly close.
• As you move from left to right across a period, the
size of the atom decreases.
 Adding electrons to same valence shell.
 Effective nuclear charge increases.
 Valence shell held closer.
Trends in Atomic Size, Continued
Group IIA
Be (4p+ and 4e-)
2e2e4 p+
2e-
Mg (12p+ and 12e-)
8e2e12 p+
2e8e-
Ca (20p+ and 20e-)
8e2e16 p+
Period 2
1e2e3 p+
2e2e4 p+
3e2e5 p+
Li (3p+ and 3e-) Be (4p+ and 4e-) B (5p+ and 5e-)
4e2e6 p+
6e2e8 p+
8e2e10 p+
C (6p+ and 6e-) O (8p+ and 8e-) Ne (10p+ and 10e-)
Practice—Choose the
Larger Atom in Each Pair.
1.
2.
3.
4.
N or F
C or Ge
N or Al
Al or Ge
Practice—Choose the
Larger Atom in Each Pair, Continued.
1.
2.
3.
4.
N or F,
F N is further left
C or Ge
Ge, Ge is further down
N or Al,
Al Al is further down & left
Al or Ge? opposing trends
Ionization Energy
• Minimum energy needed to remove an electron
from an atom.
Gas state.
Valence electron easiest to remove.
M(g) + 1st IE  M1+(g) + 1 eM+1(g) + 2nd IE  M2+(g) + 1 e-
First ionization energy = energy to remove electron
from neutral atom; 2nd IE = energy to remove from +1
ion; etc.
Trends in Ionization Energy
• As you move down a family, the IE gets
smaller.
Valence electron farther from nucleus.
• As you move from left to right across a
period, the IE gets larger.
Trends in Ionization Energy,
Continued
Practice—Choose the Atom with the
Highest Ionization Energy in Each
Pair
1.
2.
3.
4.
Mg or P
Cl or Br
Se or Sb
P or Se
Practice—Choose the Atom with the
Highest Ionization Energy in Each
Pair, Continued
1.
2.
3.
4.
Mg or P
Cl or Br
Se or Sb
P or Se ?
Metallic Character
• How well an element’s properties
match the general properties of a metal.
Metallic Character, Continued
• In general, metals are found on the left of
the periodic table and nonmetals on the
right.
• As you move left to right across the
period, the elements become less metallic.
• As you move down a column, the elements
become more metallic.
Trends in Metallic Character
Practice—Choose the
More Metallic Element in Each Pair
1.
2.
3.
4.
Sn or Te
P or Sb
Ge or In
S or Br
Example—Choose the
More Metallic Element in Each Pair
1.
2.
3.
4.
Sn or Te,
Te Sn is further left
P or Sb
Sb, Sb is further down
Ge or In
In, In is further down & left
S or Br? opposing trends
Electronegativity
• The ability of an atom to attract bonding
electrons to itself is called electronegativity
• Increases across period (left to right) and
• Decreases down group (top to bottom)
fluorine is the most electronegative element
francium is the least electronegative element
noble gas atoms are not assigned values
opposite of atomic size trend (same as electron
affinity)
Electronegativity Scale