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The Periodic Table
A Terrific Tool
Dmitri Mendeleev
• Used properties to sort into groups
• Originally based on atomic mass
In the modern table…
• Elements are arranged in order of
increasing atomic number
• Henry Mosley
Periodic Law
• When elements are arranged in order of
increasing atomic number, there is a
periodic repetition of their physical and
chemical properties.
GROUPS
PERIODS
A little review
• The number of protons in an atom (atomic
number) identifies the element
• The sum of the protons and neutrons in an
atom (mass number) identifies an isotope.
• Common notations that represent isotopes
include:

14C,
carbon-14, C-14 (where 14 is the mass
number)
An atom of C-12 and an atom
of C-14 differ in
(1)Atomic number
(2)Atomic mass
(3)Nuclear charge
(4)Number of electrons
All isotopes of a given atom
have
(1)The same mass number and same
atomic number
(2)The same mass number but different
atomic numbers
(3)Different mass numbers but the same
atomic number
(4)Different mass numbers and different
atomic numbers
In which list are the elements arranged in
order of increasing atomic mass?
(1)Cl, K, Ar
(2)Fe, Co, Ni
(3)Te, I, Xe
(4)Ne, F, Na
Elements divided into:
• METALS
• NONMETALS
• METALLOIDS
METALS
• Good conductors of heat and electric
current
• Solids at room temperature (except Hg)
• Ductile, malleable, luster
• Silvery gray color except copper and gold
Alloys
• Homogenous mixtures composed of two
or more elements, at least one of which is
a metal
• Important because their properties are
often superior to those of their component
elements
Alloys
Name
Sterling Silver
Cast iron
Stainless steel
Composition (by
mass)
Ag 92.5%
Cu 7.5%
Fe 96%
C 4%
Fe 80.6%
Cr 18.0%
C 0.4%
Ni 1.0%
NONMETALS
• Greater variation in physical properties:
many different states, many different colors
• Poor conductors
• Brittle
Activity of Ms and NMs
• Activity of METALS increases as you go
down within a group
• Activity of NONMETALS decreases as
you go down a group
What is a property of most
nonmetallic solids?
(1)High thermal conductivity
(2)High electrical conductivity
(3)Brittleness
(4)malleability
METALLOIDS
• Heavy, stair-step line
• Properties of both metals and nonmetals
• Behavior controlled by environment
 Ex. Silicon
Which list of elements
contains three metalloids?
(1)Si, Ge, Po, Pb
(2)As, Bi, Br, Kr
(3)Si, P, S, Cl
(4)Po, Sb, I, Xe
Allotropes
• Some elements exist in two or more forms
in the same phase.
• These forms differ in their molecular or
crystal structure and hence in their
properties.
Allotropes of
oxygen
Oxygen (O2)
Allotropes of carbon
Ozone (O3)
graphite
diamond
buckminsterfullerene
The P.T. displays:
• The symbols and names of the elements,
along with information about the structure
of their atoms
 Alkali metals
• Group 1
 Alkaline earth metals
• Group 2
 Halogens (halos=salt; genesis=to be born)
• Group 17/7A
 Noble Gases
• Group 18/8A
Elements can be sorted into:
•
•
•
•
Representative elements
Transition elements
Inner transition metals
BASED ON THEIR ELECTRON
CONFIGURATIONS
For Groups 1, 2 and 13-18:
• Elements within the same group have the
same number of valence electrons
(helium is the exception) and therefore
similar chemical properties.
REPRESENTATIVE
ELEMENTS
• 1A-8A
• Display a wide range of physical and
chemical properties (metals, nonmetals,
metalloids)
• s and p sublevels occupied
• Group # = # of e- in highest occupied
energy level (VALENCE)
Transition Elements
1. They are usually high melting point
metals.
2. They have several oxidation states.
3. They usually form colored compounds.
TRANSITION ELEMENTS
• Transition Metals:
 Group B elements usually displayed in main
body of a periodic table
 Copper, silver, gold and iron
 Presence of e- in d orbitals
TRANSITION ELEMENTS
• Inner Transition Elements
 Below the main body of the periodic table
 Presence of e- in f orbitals
 “rare-earth elements”
• Some more abundant than other elements
Which group of the periodic table contains
atoms with a stable outer electron
configuration?
(1)1
(2)8
(3)16
(4)18
Periodic Trends
Trends
• The succession of elements across the
same period and down the same group
demonstrate characteristic, periodic trends:




Atomic radius
Ionic radius
Electronegativity
First ionization energy
Across a Period
• There are more protons pulling on the
outer electrons
 Bigger nuclear charge
Down a Group
• Increase in the number of principle energy
levels
• SHIELDING EFFECT
Atomic Size
• Also called atomic radius
• Defined as how far the valence electrons
are from the nucleus
Atomic Size
• In general, atomic size increases from
top to bottom within a group and
decreases from left to right across a
period.
In a GROUP:
• As the Atomic # increases (top to bottom),
nuclear charge increases and the # of
occupied energy levels increases.
 Increase in (+) charge draws e- closer to the
nucleus
 Increase in the # of occupied orbitals
shields e- in the valence shell from the
attraction of p+ in the nucleus
The SHIELDING EFFECT
• blocks the attraction of the nucleus for the
outer electrons
• …is greater than the effect of the increase
in nuclear charge
• Therefore, the atomic size increases top to
bottom down a group
In a PERIOD:
• From left
•
•
to right each element has 1 more
p+ and e- across a period
e- are added to the same principal energy
level.
The shielding effect is constant for all elements
in a period. The increasing nuclear charge
pulls the e- in the valence closer to the
nucleus and the
decreases.
atomic size
Trends in Atomic Size
Which list of elements is arranged in order of
increasing atomic radii?
(1)Li, Be, B, C
(2)Sr, Ca, Mg, Be
(3)Sc, Ti, V, Cr
(4)F, Cl, Br, I
**Check Table S**
IONS
• An atom that has gained or lost one or
more electrons
• Has a positive or negative charge.
Oxidation Number
• A positive or negative number assigned to
an atom to indicate its charge when
combined in a compound
• The oxidation of an uncombined
element is zero
Oxidation Numbers
Ions- Metals
• Atoms of metallic elements tend to lose
one or more electrons and therefore form
(+) cations
 Na1+
• Electrons are pulled in much closer so the
radius decreases.
Ions- Nonmetals
• Atoms of nonmetallic elements tend to gain
one or more electrons and therefore form
(-) anions
 Cl1-
• Same e- config as a noble gas but has
fewer protons. Electrons repel each other
and the radius increases.
Ionic Size
• Cations are always smaller than that
atoms from which they form.
• Anions are always larger than the atoms
from which they form.
What is the total number of
+
electrons in a Cu ion?
(1)28
(2)29
(3)30
(4)36
What electron configuration is
correct for a sodium ion?
(1)2-7
(2)2-8
(3)2-8-1
(4)2-8-2
Ionization Energy
• The energy required to remove an
electron from an element
First Ionization Energy
• Energy to remove first electron
• Tends to decrease from top to bottom
within a group and increase from left to
right across a period
• Can help predict what ions will form (Table
6.1)
In a GROUP:
• As the size of the atom increases, nuclear
charge has a smaller effect on the electron
in the highest occupied energy levelshielding effect
• Therefore, less energy is required to
remove an electron from further energy
levels, therefore the 1st ionization energy
is lower.
From which of these atoms in the ground state
can a valence electron be removed using the
least amount of energy?
(1)Nitrogen
(2)Carbon
(3)Oxygen
(4)Chlorine
In a PERIOD:
• First i.e. tends to increase from L  R
• Nuclear charge increases; shielding effect
stays constant.
• Therefore, there is an increase in the
attraction of the nucleus for an electron,
so it takes more energy to remove an
electron from its atom
• Figure 6.19 on p.175
Electronegativity
• The ability of of an element to attract
electrons when the atom is in a
compound.
Trends in Electronegativity
• In general, electronegativity decreases
from top to bottom within a group.
• For representative elements, the values
tend to increase from left to right across a
period.
• F  Fr/Cs
Which of the following atoms has the greatest
tendency to attract electrons?
(1)barium
(2)beryllium
(3)boron
(4)bromine
Summary in Periodic Trends
• Figure 6.22 on p. 178
Reference Table S
• Table S- Properties of Selected Elements
Trends in Metallic Properties
•
•
•
•
•
•
•
Metals want to lose electrons
Form positive (+) ions (cations)
Low electronegativity
Low first ionization energy
Metallic properties decrease as you go to the
right across a period
Metallic properties increase as you go down a
group
Most metallic: francium
 most active metal
Trends in nonmetallic properties
•
•
•
•
•
Nonmetals want to gain electrons
Form negative (-) ions (anions)
High first ionization energy
High electronegativity
Nonmetallic properties increase as you
move right across a period
• Nonmetallic properties decrease as you
move down a group
• Most nonmetallic: fluorine
 most active nonmetal
Which of the following Group 15
elements has the greatest metallic
character?
(1)nitrogen
(2)phosphorous
(3)antimony
(4)bismuth
Which are two properties of most
nonmetals?
(1)High ionization energy and poor electrical
conductivity
(2)High ionization energy and good
electrical conductivity
(3)Low ionization energy and poor electrical
conductivity
(4)Low ionization energy and good electrical
conductivity