Transcript The Periodic Table

The Periodic Table
Chemistry
1
Origin of Periodic Table
 Triads
- groups of 3 elements with
similar properties
(Dobereiner – 1817)
of Octaves – properties of
elements repeat every 8 elements
(Newlands – 1863)
 Law
2
Origin of Periodic Table
Mendeleev – 1869
–Properties of elements are periodic
functions of their atomic masses.
–Developed 8 column table
–Left spaces for undiscovered
elements
–Columns contained elements with
similar properties
–Problems with Ni, I, K (Why?)
 Dimitri
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Origin of Periodic Table
 X-ray
experiments by Mosley
(1913) led to discovery of atomic
numbers.
Periodic Law – properties
of elements are periodic functions
of their atomic numbers.
 Modern
4
Organization of Periodic Table
 Rows
are called periods.
 Columns are called families or
groups.
 All elements in a family have similar
properties.
 Octet Rule – elements with 8 valence
electrons are unreactive
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Periodic Table
Rows = Periods
Columns = Families or Groups
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Chemistry Chapter 5
The Periodic Law
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Mendeleev’s Periodic Table
Dmitri Mendeleev
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Periodic Table with Group Names
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
Alkali Metals
 1st column in blue
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The Properties of a Group:
the Alkali Metals
Easily lose valence electron
(Reducing agents)
React violently with water
Large hydration energy
React with halogens to form salts
H- Hydrogen
Rb- Rubidium
Li-Lithium
Cs- Cesium
Na-Sodium
Fr-Francium
K-Potassium
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Properties of Metals
 Metals are good
conductors of heat and
electricity
 Metals are malleable
 Metals are ductile
 Metals have high tensile
strength
 Metals have luster
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Examples of Metals
Potassium, K
reacts with
water and
must be
stored in
kerosene
Copper, Cu, is a relatively soft
metal, and a very good electrical
conductor.
Zinc, Zn, is
more stable
than potassium
Mercury, Hg, is the only
metal that exists as a
liquid at room temperature
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
Alkaline Earth Metals
 2nd column - green
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Properties of alkaline metals
Be, Mg, Ca, Sr, Ba, Ra
 The alkaline earth metals, or alkaline
earths, are beryllium, magnesium,
calcium, strontium, barium, and radium.
 Possess many properties of metals
 Low electro negativities
 Low electron affinities
 They have smaller atomic radii than the
alkali metals
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
Transition Metals all have similar properties
 Middle – purple
and can give up different
amounts of electrons at different times
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Properties of Metalloids
B- Boron As- Arsenic At- Astatine
Ge- Germanium Te-Tellurium
Sb- Antimony Si- Silicon
Al-Aluminum Po- Polonium
Metalloids straddle the
border between metals
and nonmetals on the
periodic table.
 They have properties of both metals and
nonmetals.
Metalloids are more brittle than metals, less
brittle than most nonmetallic solids
 Metalloids are semiconductors of electricity
 Some metalloids possess metallic luster
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Silicon, Si – A Metalloid
 Silicon has metallic luster
 Silicon is brittle like a nonmetal
 Silicon is a semiconductor of
electricity
Other metalloids include:





Boron, B
Germanium, Ge
Arsenic, As
Antimony, Sb
Tellurium, Te
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Properties of Nonmetals
Carbon, the graphite in “pencil lead” is a great
example of a nonmetallic element.
 Nonmetals are poor conductors of heat and
electricity
 Nonmetals tend to be brittle
 Many nonmetals are gases at room
temperature
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Examples of Nonmetals
Sulfur, S, was
once known as
“brimstone”
Microspheres
of phosphorus,
P, a reactive
nonmetal
Graphite is not the only
pure form of carbon, C.
Diamond is also carbon;
the color comes from
impurities caught within
the crystal structure
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
Non-Metals
 Right of the stair-step line
C-Carbon, N- Nitrogen, O-Oxygen, PPhosphorus, Cl-Chlorine, Se-Selenium
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Halogens
 7th tall column (light orange)

F-fluorine Cl-Chlorine Br-Bromine
 I- Iodine
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Properties of Halogens
a particular class of nonmetals.
 Very high electronegativities
 Seven valence electrons (one short of a
stable octet)
 Highly reactive, especially with alkali
metals and alkaline earths
 Halogens range from solid (I2) to liquid
(Br2) to gaseous (F2 and Cl2) at room
temperature.

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Noble Gases
 last tall column (yellow)



He-Helium Ne-Neon Ar-Argon
Kr-Krypton Xe-Xenon
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Properties of Noble gases
Unreactive gases
 Odorless
 Colorless
 All produce light when an electric
current is applied

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Lanthanides – Ce row
 Actinides – Th row

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Determination of Atomic Radius:
Half of the distance between nucli in
covalently bonded diatomic molecule
"covalent atomic radii"
Periodic Trends in Atomic Radius
Radius decreases across a period
Increased effective nuclear charge due
to decreased shielding
Radius increases down a group
Addition of principal quantum levels
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Table of
Atomic
Radii
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Ionization Energy - the energy required to remove an
electron from an atom
Increases for successive electrons taken from
the same atom
Tends to increase across a period
Electrons in the same quantum level do
not shield as effectively as electrons in
inner levels
Irregularities at half filled and filled
sublevels due to extra repulsion of
electrons paired in orbitals, making them
easier to remove
Tends to decrease down a group
Outer electrons are farther from the
nucleus
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Electron Affinity - the energy change associated
with the addition of an electron
Affinity tends to increase across a period
Affinity tends to decrease as you go down
in a period
Electrons farther from the nucleus
experience less nuclear attraction
Some irregularities due to repulsive
forces in the relatively small p orbitals
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Table of Electron Affinities
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Ionic Radii
Cations
Anions
Positively charged ions
Smaller than the corresponding
atom
Negatively charged ions
Larger than the corresponding
atom
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Summation of Periodic Trends
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Table of Ion Sizes
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Electronegativity
A measure of the ability of an atom in a chemical
compound to attract electrons
Electronegativities tend to increase across
a period
Electronegativities tend to decrease down a
group or remain the same
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Periodic Table of Electronegativities
36