physical science 5.1 : arranging the elements
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THE PERIODIC TABLE
Physical Science
Chapter 5
ARRANGING THE ELEMENTS
Physical Science
Chapter 5.1
Objectives:1. Describe how Mendeleev arranged
elements in the first periodic table.
2. Explain how elements are arranged in the modern periodic table.
3. Compare metals, nonmetals, and metalloids based on their properties and on their location in the periodic table.
4. Describe the difference between a period and a group.
Discovering a Pattern In 1869, Russian chemist Dmitri
MendeleevArranged the elements in order of
increasing atomic mass. Periodic Properties of the
ElementsWhen the elements are arranged
in order of increasing atomic mass○ Those that had similar properties
occurred in a repeating pattern.○ These repeating patterns are
periodic, meaning that they happen at regular intervals.
Predicting Properties of Missing ElementsMendeleev’s arrangement had gaps in its pattern.
○ Mendeleev predicted that elements yet to be found would fill these gaps.
○ He also predicted the properties of the missing elements.By 1886, all of the gaps had been filled and Mendeleev’s
predictions were right.
Changing the Arrangement A few elements’ properties did not fit in the pattern of Mendeleev’s table. In 1914,
British scientist Henry Moseley found the number of protons—the atomic number—in an atom.
When the elements were arranged by atomic number, they fit the pattern in Mendeleev’s table.
Periodic Law: physical and chemical properties of the elements are periodic functions of their atomic numbers.
Classes of Elements Elements are classified as:
MetalsNonmetalsMetalloids
The number of electrons in the outer energy levelOne characteristic that helps determine which
category an element belongs in. The zigzag line on the periodic table
Can help you recognize which elements belong in which category.
Metals: Found to the left of the zigzag line. Atoms of most metals have few electrons in
their outer energy level. All metals are
ShinyDuctileMalleableGood conductors of electric current and thermal
energy.
Nonmetals Found to the right of the zigzag line. Atoms of most nonmetals have an almost
complete set of electrons in their outer energy level.
Nonmetals are:Not shinyNot ductile, or malleablePoor conductors of electric current and thermal energy.
Metalloids The elements that border the zigzag line. Atoms of metalloids have about half of a
complete set of electrons in their outer energy level.
have some properties of metals and some properties of nonmetals.also called semiconductors
Decoding the Periodic Table Each Element is Identified
by a Chemical SymbolEach square on the periodic
table includes○ Element’s name○ Chemical symbol○ Atomic number○ Atomic mass.
For most elementsThe chemical symbol has one
or two letters.The newest elements have
temporary three-letter symbols.
6
C 12.011 Carbon
Atomic number
Chemical Symbol
Atomic Mass
Element Name
Horizontal rows Are Called Periods The chemical and physical properties of elements in a
row follow a repeating pattern as you move across the period.
Vertical columns Are Called GroupsElements in the same group often have similar
chemical and physical properties.
Group
Period
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