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Periodic Law
Chapter 6
Objectives
1. History of the Periodic table
2. Start talking about Periodic trends
3. Periodic Table Geography … families of
elements
1790 Antoine Lavoisier – Compiled a list of
known elements – 23
1864 John Newlands – 1st proposed
organizational scheme for elements
Dmitri Mendeleev – Russian
Chemist who first developed
the Periodic Table.
Mendeleev’s Periodic Table –
elements are arranged according
to increasing atomic mass
1st Draft
Version of
Mendeleev’s
table
In 1913 Henry Moseley conducted
X-ray experiments on elements.
The outcome of his work was the
introduction of the atomic number.
It was found that if Mendeleev's table was
ordered by atomic number instead of
atomic mass the inconsistencies in the
table were eliminated.
This is the blueprint for the modern
periodic table.
Periodic Law – The
physical and chemical
properties of the
elements are periodic
functions of their
atomic numbers.
Periodic Trends
Atomic Radii –The
size of an atom –
one half the
distance between
the nuclei of two
identical atoms
bonded together
Atomic Radii
• Decreases as you go across a period due to
the added positive charge to the nucleus.
• Increases down a group due to the “shielding
effect” caused by the addition of new energy
levels. The inner energy levels act in a way to
shield the attractive charges of the nucleus for
the outer electrons.
Periodic Table
Geography
The horizontal rows of the periodic table
are called PERIODS.
The elements in any group
of the periodic table have
similar physical and chemical
properties!
The vertical columns of the periodic table
are called GROUPS, or FAMILIES.
Alkali Metals
Alkaline Earth Metals
Transition Metals
These elements are also
called the rare-earth
elements.
InnerTransition Metals
Halogens
Noble Gases
S block
P block
D block
F block
Group Properties of Some Main
Group Elements
Alkali metals
Halogens
Alkaline Earth Metals
Halogens 2
Noble Gases
Braniac Alkali Metals