Transcript periodic table of the elements

ARRANGING THE
ELEMENTS
CHAPTER 7 - 1
DISCOVERING A PATTERN
• Dmitri Mendeleev, a
Russian chemist,
discovered a pattern to
the elements in 1869.
• After trying several
ways, he finally arranged
the known elements by
the increasing atomic
mass.
Periodic Properties
of the Elements
• When arranged by atomic mass, the
elements fell into a repeating pattern of
properties called “periodic.”
• Mendeleev found that the elements’
properties followed a pattern that
repeated every 7 elements.
• His table became known as the periodic
table of the elements.
Predicting Properties of
Missing Elements
• His arrangement had gaps between
the known elements.
• Mendeleev predicted that elements
would be found to fill the gaps.
• He used the pattern to predict the
missing element’s properties.
CHANGING THE
ARRANGEMENT
• All the elements’ properties
didn’t fit.
• In 1914, Henry Moseley, a
British scientist, determined
the number of protons, the
atomic number, in an atom.
• When arranged by atomic
number, all the elements fit
the pattern.
PERIODIC TABLE AND
CLASSES OF ELEMENTS
• Elements are classified according to
their properties.
• The classes are metals, metalloids, and
nonmetals.
GALLIUM
SILICON
PHOSPHORUS
METALS
• Most elements are metals.
• They have few electrons in their outer
energy level.
• Metals are shiny, malleable, ductile, and
are good conductors of electricity and
heat.
NONMETALS
• Atoms of most nonmetals
have an almost complete set
of electrons in their outer
level.
• More than half of the
nonmetals are gases at
room temperature.
• Nonmetals are not
malleable or ductile, and if
solid, they can be brittle.
METALLOIDS
• Metalloids border the zigzag line on the
periodic table.
• They have half a complete set of electrons in
their outer level.
• They have some properties of metals and
some of nonmetals.
Chemical Symbols
• Each square on the periodic table includes
an element’s name, chemical symbol, atomic
number, and atomic mass.
• The chemical symbol has one or two
letters. Example: hydrogen is H and
helium is He.
Periods
• Each horizontal row of elements on the
periodic table is called a period.
• The elements in each row follows a
repeating pattern of properties.
Groups
• Each vertical column
of elements on the
periodic table is called
a group.
• These often have the
same chemical and
physical properties.
• They are sometimes
called a family
because they share
similar properties.
Atomic Number
• The atomic number is the number
of protons or electrons in the
element.
• The atomic number is above the
chemical symbol.
LET’S TRY IT!
Lab: Create a
Periodic Table