PERIODIC TABLE OF
ELEMENTS
Module 3
Enhanced Science
Grade 8

Elements Known Throughout
History:

JOHANN DOBEREINER (1817)
• a German chemist who formed the
triads of elements with similar
properties.

JOHN NEWLANDS (1863)
• an English chemist proposed the
Law of Octaves.
• He based his classification of
elements on the fact that similar
properties could be noted for every
eight element when they are arranged
in order of increasing atomic masses.

Lothar Meyer and Dmitri
Mendeleev
• They both came up with periodic tables that showed
how elements should be grouped.
• Both scientists were teachers living and working in
different places.
– Meyer lived and worked in Germany
– Mendeleev in Russia.
• Both arranged the elements in order of increasing
atomic mass while putting in groups those with similar
properties.
• Both of them also left blank spaces in their tables,
believing that these spaces would be filled later with
elements yet to be discovered.

Dmitri Ivanovich Mendeleev
• Father of the Periodic Table
• He noticed patterns in the properties and atomic
weights of halogens, alkali metals and alkaline
metals.
• In an effort to extend this pattern to other
elements, he created a card for each of the 63
known elements.
• he developed his statement of the periodic law
and published his work.
• One vote shy of being awarded the Noble Prize for
his work in chemistry.

Mendeleev’s Table (in German)

Henry Moseley (1914)
• an English physicist observed that the
order of the X-ray frequencies emitted by
elements follows the ordering of the
elements by atomic number.
** This observation led to the development
of the MODERN PERIODIC LAW which
states that “the properties of elements vary
periodically with atomic number.”

MODERN PERIODIC
TABLE
---organizes elements in such a way that
information about the elements and their
compounds are easily revealed

MODERN PERIODIC TABLE
• The vertical columns of the periodic table,
called GROUPS, identify the principal
families of elements. Some families have
their special names.

MODERN PERIODIC TABLE
• The horizontal rows or PERIODS are
numbered from the top to bottom.
Examples:
the elements lithium (Li) across neon (Ne)
form Period 2.There are 7 horizontal rows or
periods in the periodic table.

MODERN PERIODIC TABLE
• The elements are grouped into blocks or
series in the periodic table.
Group 3 to Group 12 constitutes one block
wherein elements in this block are referred as the
transition elements.
The lanthanides and actinides are special
series of elements but are also part of the
transition block; they are also called the inner
transition elements.
Elements from the taller columns (groups 1, 2,
and 13 through 18) are called the representative
elements or main groups of the periodic table.

Types of Elements
1. Metals: elements that have luster, are malleable and ductile,
and are good conductors of heat & electricity. (left, in blue)
2. Nonmetals: elements that are usually brittle solids or gases
at room temperature and poor conductors. (right, in yellow)
3. Metalloids: elements that share some properties with metals
and some with nonmetals. (stair-step, under gases, in green)
4. Representative
elements:
columns 1 & 2,
13 – 18
5. Transition
elements:
columns 3 – 12
6. Inner Transition
elements: below
the main table

REACTIVITY
The ease and speed with which a metal
reacts with another substance.
• Metals vary in reactivity.
• The most reactive metals will react even with
cold water while the least will not react even
with acid.
• The reactivity of metals can cause
deterioration of materials.
**The gradual wearing away of a metal due to
interaction with other substances is called
CORROSION.

REACTIVITY
• Metallic character increases from top to bottom
and decreases from left to right;
• nonmetallic character decreases from top to
bottom and increases from left to right, as seen
in the figure on the right.

LOSE AND GAIN OF
ELECTRON
• Metallic property relates to how easy it is for
an atom to lose an electron.
• nonmetallic property relates to how easy it is
for an atom to gain an electron.
** when an atom loses electrons, a cation is
formed.
**some nonmetals, tend to gain electrons thus
forming anions.
**The formation of ions among the elements
results in the formation of many different
compounds.

ELECTRON SHELLS
where electrons occupy regions around the
nucleus called electron shells.
These are also called energy levels because
each electron shell corresponds to a
particular energy.
Each electron shell can hold only a certain
number of electrons.
The way the electrons of an atom are
distributed in the various energy levels or
electron shells is called ELECTRONIC
CONFIGURATION.

VALENCE SHELL
• The highest energy level that an electron
occupies is referred to as the outermost
shell or VALENCE SHELL.
• The electrons in the valence shells are
called VALENCE ELECTRONS. These
electrons are the ones involved in
chemical reactions. The chemical
properties of an element depend on the
number of valence electrons

FAMILIES OF ELEMENTS

Alkali Metals: Group 1 (1a)
• Silvery solid; soft compared to other metals
• Low density and low melting point
• Extremely reactive; especially in water
• 1 valence electron
• Very easy to lose 1 electron
• Reactivity
INCREASES as you
go down the family.
• Francium is much
more reactive than
Lithium.
• Hydrogen is not a
metal but is grouped
here because of its
number of valence
electrons.

Alkaline Earth Metals: Group 2 (2a)
• Denser, harder, higher melting point than group 1
• Conducts electricity well
• Very reactive but not as much as group 1
• 2 valence electrons
– Easy to lose 2 electrons
• Reactivity
INCREASES as
you go down the
family.
• Radium is much
more reactive than
Beryllium.

Boron Family: Group 13 (3a)
• Metals except for Boron, which is a metalloid
• These elements are used in a variety of products
• Reactive; Bonds with other elements by sharing
electrons.
• 3 valence electrons
– Needs to lose 3 electrons
• Reactivity
INCREASES
as you go
down the
family.
- Thallium is
more reactive
than Boron.

Carbon Family: Group 14 (4a)
• Metals, nonmetals, and metalloids
• Bond with many elements by sharing electrons
• Silicon is a semiconductor:
– Extremely abundant metalloid
– Used in computer chip manufacturing – “Silicon Valley”
• 4 valence electrons
-Lose 4 or gain 4;
same difference

Nitrogen Family: Group 15 (5a)
• Metals, Nonmetals, and
Metalloids
• Reactive: Bonds with other
elements by sharing
electrons
• Useful to living things in
small amounts; deadly in
large amounts
• 5 valence electrons
– Needs to gain 3 electrons
• Reactivity DECREASES as
you go down the family.
– Nitrogen is more reactive
than Bismuth.

Oxygen Family: Group 16 (6a)
• Nonmetals and Metalloids
• Oxygen & Sulfur are essential for life; Selenium
conducts electricity when exposed to light
• Very reactive
• 6 valence electrons
– Easy to gain 2 electrons
• Reactivity
DECREASES
as you go down
the family.
• Oxygen is more
reactive than
Polonium.

Halogens: Group 17 (7a)
• Nonmetals, except Astatine (radioactive metalloid)
• Halogen means “salt-former”
• Highly reactive
• 7 valence electrons
– Very easy to gain 1 electron to fill shell
• Reactivity
DECREASES as
you go down the
family.
1. Fluorine is
extremely reactive,
whereas Iodine is
the least reactive.

Noble Gases: Group 18 (8a)
• Nonmetals
• Inert; they do not react with other elements
• Used in various types of lighting
• 8 valence electrons (orbital is full)
• Helium is less
dense than air
and is used in all
types of balloons.
• Helium is safer
than hydrogen,
because
Hydrogen
catches fire.

Transition Elements: Groups 3 – 12
• All are metals; shiny, hard, lustrous
• Most are found combined with other elements in ores
• Most have higher melting pts than Representative E
• Mercury is the only liquid at room temperature
Transition Elements
(in yellow)
• Special groups:
(‘group’ does not
refer to a column.)
1. Iron Triad: Iron,
Cobalt, Nickel
2. Platinum Group:
Ruthenium,
Rhodium,
Palladium,
Osmium, Iridium,
Platinum

Inner Transition Elements
A. Found below the main table.
B. Lanthanides: naturally occurring except Promethium
1. Soft metals; can be cut w/a knife
2. Very similar; hard to separate when together as an ore
C. Actinides: synthetic (except Thorium, Protactinium,
Uranium)
1. Radioactive
2. Unstable nuclei; decay to form other elements