Eight Grade Science
Periodic Table
Dmitri Mendeleev
Old Periodic Table
New Periodic Table
How has the periodic table
changed over the years?
How to read the periodic table of
elements
Groups/ families and Periods
Detailed Information
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Elements can be organized by group or period, but they
also can be placed into three distinct groups: metals, semimetals, and non-metals.
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Metals are the pink section on the left side of . Metals are
generally lustrous solids, often deformable (though
mercury (Hg) is a liquid at room temperature). Metals are
highly conducive to both heat and electricity.

Nonmetals are the blue boxes on the upper right hand of
the periodic table. More than half of the non-metals are
gaseous at normal temperatures.
Types of Elements

Semimetals are the green boxes on the
periodic table. As their transitory name
and placement on the periodic table
suggest, they exist in between the
distinctions of metals and nonmetals.

Metals and Nonmetals- Most chemical
compounds are formed by the interactions
between metals and non- metals.
Types of Elements

Atomic Size (Atomic Radius)
The atomic size of an atom, also called the atomic radius, refers to the
distance between an atom's nucleus and its valence electrons. Remember, the
closer an electron is to the nucleus, the lower its energy and the more tightly it
is held.

Moving Across a Period
Moving from left to right across a period, the atomic radius decreases. The
nucleus of the atom gains protons moving from left to right, increasing the
positive charge of the nucleus and increasing the attractive force of the nucleus
upon the electrons. True, electrons are also added as the elements move from
left to right across a period, but these electrons reside in the same energy
shell and do not offer increased shielding.
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Moving Down a Group
The atomic radius increases moving down a group. Once again protons are
added moving down a group, but so are new energy shells of electrons. The
new energy shells provide shielding, allowing the valence electrons to
experience only a minimal amount of the protons' positive charge.
Periodic Table Placements
Atomic Size and Ionization
Things to Remember
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Body Size =Atomic Mass
(increases left to right)
# of Arms =Energy Levels occupied
(row 1, 1) (row 2, 2) and so on
# of Fingers = Atomic #
(# of Protons)
# of Hairs = # of electrons in outer valence
electron shell ( increase left to right)
The Missing Link
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What was observed about the size of the
aliens as their pictures were arranged?
How can this be compared to the periodic
table?
By relating the order of the aliens to the
periodic table, infer the significance of the
number of arms, fingers, and hairs on each
alien.
Describe everything you know about the
“missing link” alien.
Draw the missing alien.
Analysis