CHAPTER 5 REVIEW
THE PERIODIC TABLE
CHAPTER 5 REVIEW
• Mendeleev arranged the known chemical
elements in a table according to increasing mass.
• When Mendeleev organized elements in his
periodic table in order of increasing mass, elements
with similar properties were in the same column, or
group.
• Mendeleev gave the name eka-aluminum to an
unknown element he predicted would have
properties similar to those of aluminum. This element
was later discovered and named gallium.
• The usefulness of Mendeleev’s periodic table was
confirmed by the discovery of elements with
predicted properties.
CHAPTER 5 REVIEW
• In a periodic table, a set of properties repeats from
row to row. This is called the periodic law.
• In the periodic table, the rows are called periods
and the columns are called groups.
• The modern periodic table is organized by
increasing atomic number.
• The atomic mass unit is based on 1/12th the mass of
a carbon-12 atom.
• The atomic mass of an element is the weighted
average of the masses of an element’s isotopes.
CHAPTER 5 REVIEW
• There are three classes of elements: metals,
nonmetals, and metalloids
• Metals conduct heat and electricity, are malleable,
and are ductile. All metals except mercury are
solids at room temperature.
• Nonmetals do no conduct heat or electricity, and
they are brittle. Many nonmetals are gases at room
temperature.
• Metalloids can have properties of both metals and
nonmetals.
CHAPTER 5 REVIEW
• The metals are on the left side of the stair-step line
on the periodic table.
• The nonmetals are on the right side of the stair-step
line on the periodic table.
• The metalloids are either right above or right below
the stair-step line.
• As you move across a period from left to right, the
elements become less metallic and more
nonmetallic.
CHAPTER 5 REVIEW
• Valence electrons: electrons in the highest
occupied energy level of an atom
• The chemical properties of elements are
determined by their valence electrons.
• Elements in a group have similar properties because
they have the same number of valence electrons
• The number of valence electrons in a Group A
elements matches its group number
CHAPTER 5 REVIEW
• Group 1A
• Alkali metals
• 1 valence electron
• Reactivity increases going
down
• Group 2A
• Alkaline earth metals
• 2 valence electrons
• Group 7A
• Halogens
• 7 valence electrons
• Reactivity decreases going
down
• Group 8A is called the
noble gases.
• Noble gases
• 8 valence electrons (He
has 2)
• Emit color when electric
current is applied
CHAPTER 5 REVIEW
• Some highly reactive elements are stored in argon
gas to protect them.
• Carbon is in most of the compounds in your body
except water.