Faculty of Biotechnology
General Chemistry
Lecture 3
Periodic Table of
Elements
Dr. M. Abd-Elhakeem
Mendeleev
• In 1869, Dmitri Ivanovitch
Mendeléev created the first accepted
version of the periodic table.
• He grouped elements according to
their atomic number, and as he did,
he found that the families had
similar chemical properties.
• Blank spaces were left open to add
the new elements he predicted would
occur.
• A periodic table is a tabular display of the
chemical elements, organized on the basis of
their atomic numbers.
• The main body of the standard form of table
is an 18 groups (columns) and 7 periods
(rows).
Families
• Columns of elements are called groups or
families.
• Elements in each family have similar but not
identical properties.
• For example, lithium (Li), sodium (Na),
potassium (K), and other members of family IA
are all soft, white, shiny metals.
• All elements in a family have the same number
of valence electrons.
Periods
• Each horizontal row of elements is called a
period.
• The elements in a period are not alike in
properties.
• In fact, the properties change greatly across even
given row.
• The first element in a period is always an
extremely active solid. The last element in a
period, is always an inactive gas.
• Three major classes are immediately
recognized.
– Metals
– non-metals
– Metalloids
Properties of Metals
• Good conductors of heat and
electricity.
• Shiny.
• Ductile (can be stretched into
thin wires).
• Malleable (can be pounded
into thin sheets).
• A chemical property of metal
is its reaction with water which
results in corrosion.
Properties of Non-Metals
• Poor conductors of heat
and electricity.
• Not ductile or malleable.
• Solid non-metals are
brittle and break easily.
• Dull.
• Many non-metals are
gases.
Sulfur
Properties of Metalloids
Silicon
• Metalloids (metal-like) have
properties of both metals and
non-metals.
• They are solids that can be
shiny or dull.
• They conduct heat and
electricity better than nonmetals but not as well as
metals.
• They are ductile and
malleable.
Famous groups and periods
1.
2.
3.
4.
5.
6.
7.
Alkali metals (Group IA)
Alkaline Earth Metals (Group IIA)
Halogens (Group VIIA)
Nobel gases (Group VIIIA)
Transition metals
Lanthanides
Actinides.
Alkali Metals
• The alkali family is found in the first column
of the periodic table.
• Atoms of the alkali metals have a single
electron in their outermost level (s subshell),
in other words, 1 valence electron.
• They are shiny, have the consistency of clay,
and are easily cut with a knife.
Alkali Metals
• They are the most reactive metals.
• They react violently with water to
form alkali.
• Alkali metals are never found as free
elements in nature. They are always
bonded with another element.
Alkaline Earth Metals
• They are never found uncombined in
nature.
• They have two valence electrons.
• Alkaline earth metals include magnesium
and calcium, that present commonly in
earth crust.
Transition Metals
• Transition Elements locate in the middle of the
periodic table
• These are the metals you are probably most
familiar: copper, tin, zinc, iron, nickel, gold,
and silver.
Transition Metals
• The compounds of transition metals are
usually brightly colored and are often used to
color paints.
• Transition elements have more than one
valence and so you must calculate the
oxidation state in each compound
Transition Elements
Many transition metals combine
chemically with oxygen to form
compounds called oxides.
Halogen Family
• The elements in this family are fluorine,
chlorine, bromine, iodine, and astatine.
• Halogens have 7 valence electrons, which
explains why they are the most active nonmetals. They are never found free in nature.
• Halogen atoms only need to gain 1 electron
to fill their outermost energy level. i.e.
oxidation state = -1
• They react with alkali metals to form salts.
• They are gases
Noble Gases
• Noble Gases or inert gases are colorless gases that
are extremely un-reactive.
• One important property of the noble gases is their
inactivity. They are inactive because their outermost
energy level is full.
• The family of noble gases includes helium, neon,
argon, krypton, xenon, and radon.
• All the noble gases are found in small amounts in
the earth's atmosphere.
• Note that There are four distinct
rectangular areas or blocks.
• s block
• p block
• d block
• The f-block is usually not included in the
main table, but rather is floated below.
s block elements
d block elements
p block elements
f block elements
Periodicity of chemical
properties
1- Atomic radius:
the atomic radii decrease in going from left to right across
a given period.
Atomic radii increase from top to bottom down a group
2- Ionization Energy
Ionization energy is the amount of energy required to
remove an electron from a gaseous atom or ion.
Ionization energy generally increases from left to right
across periods and decrease from top to bottom down
groups.
Electronegativity
• It is the tendency of an atom or a functional
group to attract electrons
• electronegativity increases on passing from left
to right along a period, and decreases on
descending a group
Polarity
• It is the charged pole in the compounds due to
difference in electron negativity and the
asymmetry of the compound's structure
Water is a polar
molecule
Methane is nonpolar molecule
Solubility
• Solubility is defined as the maximum mass of
a substance that can be dissolved in a fixed
mass of a solvent at a given temperature.
• A substance will have a different solubility in
different solvents depending on polarity of
both the substance and the solvent.
• Still remember about ”like dissolves like”?
Factors affecting solubility
1. Temperature
2. Pressure
3. Polarity of solvent and solute
Name
Solubility in water
Exception
Nitrates,
acetates, Soluble
perchlorates
Ag+ for acetate
sulphates
Ba+2, Pb+2, Hg+2,
Ca+2, Ag+1, and
Sr+2
Soluble
Chlorides, bromides, Soluble
iodides
Pb+2, Ag+2, Hg+2
Carbonates,
phosphates,
Sulfites,
Sulphides
Alkali metal
ammonium
Hydroxides,
chromates
, Insoluble
Insoluble
and
Ba+2, Sr+2, and Ca+2
• In fact you can predict most of physical
properties of any unknown element only by its
position in the periodic table.
• Ex. Predict the physical and chemical properties
of 55Cs
Atomic Mass Unit (AMU)
• The unit of
measurement for an
atom is an AMU. It
stands for atomic mass
unit.
• One AMU is equal to
the mass of one proton.
Atomic Mass Unit (AMU)
• There are
6 X 1023 or
600,000,000,000,000,0
00,000,000 amus in
one gram.
• (Remember that
electrons are 2000
times smaller than one
amu).
Calculation of molecular weight