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Regents Chemistry Review By Topic: Chemical Periodicity

On Periodic Table elements are arranged in order of increasing atomic number.

The columns on the Periodic Table are called Groups. Elements that are in the same group have similar chemical properties because they have the same number of valence electrons.

The rows on the Periodic Table are called Periods.

Periodic Table has a staircase on the right side (the zig zag line). Elements to the left of the staircase are called metals. Elements to the right of the staircase are called nonmetals. Elements on the staircase are called metalloids. These include : B, Si, Ge, As, Sb, Te.


Group 18 elements are called noble gases. These elements tend not to react with other elements because they already have a full octet (8 valence electrons in their outer shell).


Properties of metals: malleable ( can be hammered into sheets), good conductors of heat and electricity, low ionization energy, low electronegativity and ductile (can be made into wires). Metals tend to lose electrons. The oxidation numbers of elements are on the top right corner for each element.

Properties of nonmetals: high ionization energy, high electronegativity, poor conductors of heat and electricity. Nonmetals tend to gain electrons.


Atomic Radius is the distance from the nuclear until the outer electron shell.

Atomic radius increases from to the left and down on the Periodic Table.


Ionization energy is the amount of energy needed to remove the most loosely held electron from a gaseous atom in the ground state. Ionization energy increases to the right and up on the Periodic Table.


Electronegativity is a scale that measures the attraction of an element for electrons. Electronegativity increases to the right and up on the Periodic Table (except group 18). Fluorine is the most electronegative element.


If you did not memorize these trends for the Regents Exam, you can use Table S to figure out the trends!

Table S on the Reference Table shows ionization energy, electronegativity, electronegativity, melting point, boiling point, density and atomic radius of each element.


Atoms Vesus Ions

An atom that either loses or gains electrons is called an ion.

If an atom loses electrons, it will become positively charged (charge or oxidation number can be seen on top right of each element on the Periodic Table). When an atom loses electrons its radius decreases.

An atom that gains electrons becomes negatively charged and its radius increases.


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