The Periodic Law

Periodic Table of Elements

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Development of the Periodic Table

Dmitri Mendeleev developed the first periodic table

The periodic table is an arrangement of elements according to their chemical and physical properties

Mendeleev’s Periodic Table

Mendeleev arranged the elements according to their atomic masses

The elements followed a pattern of 1 2 3 4 3 2 1 (valence electrons)

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Questions

Who developed the first periodic table?

What is the periodic table?What are valence electrons?How did Mendeleev arrange

elements in the first periodic table?

Periodic

Refers to repeating according to a pattern

Questions

Why are the days of the week and the months of the year periodic?

Modern Periodic Tablevideo

Henry Moseley determined the atomic number of the elements

Elements in the modern periodic table are arranged according to atomic numbers

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Periodic Law

States that the physical and chemical properties of elements are periodic functions of their atomic numbers

Properties of elements have some pattern according to their atomic numbers

Questions

What is the major difference between Mendeleev’s periodic table and the modern periodic table?

Columns in the periodic table

Columns of elements are known as groups or families

Elements in a family have similar properties

Rows in the periodic table

The horizontal rows of elements are called periods

The elements in a period do NOT have similar properties

Periods

First element in a period is an active solid

Last element in a period is an inactive gas

Questions

What is the major difference between periods and families?

How are elements in a family similar?

How are elements in a period different?

Element squares in the periodic table

The basic information found in each square of the periodic table :

Atomic number Chemical symbol Element name Atomic mass video

Elements

Elements are classified as:

Metals NonmetalsMetalloids

Questions

What information is found in the squares on the periodic table?

How can an element be classified?

Characteristics of Metals (video)

Good conductors of heat and electricity

Shiny; High melting pointsMalleable (bends easily) Ductile (can be made into

wires)Found on the LEFT of the

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Questions

What is the difference between ductile and malleable?

Where are metals found on the periodic table?

Properties of Nonmetals

DullBrittle (hard/ easily broken)Found on the RIGHT of the

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Properties of Metalloids

Has properties of both metals and nonmetals

Found touching the dark, zig-zag line

Metalloid means “metal-like”video

Questions

What is a metalloid?Where are metalloids located

in the periodic table?Where are nonmetals

located on the periodic table?

Periodic Properties of Elements (Modern Table)

Valence pattern across a period is 1 2 3 4 3 2 1 0 (left to right)

Metals lose electrons easilyNonmetals gain electrons easily

Periodic Properties of Elements

The size of the atom decreases from left to right across a period

The metallic properties of elements decrease from left to right across a period

Elements on the left are more reactive than the elements on the right

Questions

What happens to metallic properties as one moves from left to right across a period?

What is the valence pattern of electrons across a period?

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