5.1 Organizing the Elements
The Search for Order
Until 1750, only 17 elements identified
1789, Lavoisier grouped elements
–metals, nonmetals, gases, earths
Mendeleev’s Proposal
1860s Mendeleev: solitaire, ____________________
5.1 Organizing the Elements
Mendeleev’s Periodic Table
• Periodic table: arranges elements based on_________
–Column: masses______________from top to bottom
Mendeleev’s Prediction
• Many elements had not been discovered= several ____
• Predict properties for_____________________elements
• Named missing elements after elements in same group
5.1 Organizing the Elements
Mendeleev’s Periodic Table
Example: He gave the name eka-aluminum to the
missing element one space below aluminum in the
table. Predicted to be:
• be a soft metal,
• have a low melting point, and
• have a density of 5.9 g/cm3
In 1875, French chemist discovered Gallium:
• is a soft metal,
• has a melting point of 29.7°C, and
• has a density of 5.91 g/cm3
5.1 Organizing the Elements
Mendeleev’s Periodic Table
Scientists use the periodic table to explain_________
behaviors of different groups of elements.
• The properties of gallium are remarkably similar to the
predicted properties of eka-aluminum.
• Scientists concluded that gallium and eka-aluminum are
the same element.
• The discovery of scandium (Sc) in 1879 and the
discovery of germanium (Ge) in 1886 provided more
evidence.
5.1 Organizing the Elements
Mendeleev’s Periodic Table
Example: Heat from a hand can melt gallium. In
some traffic signals, there are tiny light emitting
diodes (LEDs) that contain a compound of gallium.
5.1 Organizing the Elements
The eight-note interval between any two notes on a keyboard
with the same name is an octave. The sounds of musical notes
that are separated by an octave are related, but they are not
identical. In a similar way, elements in the same column of the
modern periodic table are related but not identical.
5.1 Organizing the Elements
The Periodic Law
• Elements are arranged by increasing atomic
___________________.
• Properties of elements repeat in a____________
way when atomic numbers are used to arrange
elements into groups.
5.1 Organizing the Elements
The Periodic Law
Periods:
Each__________in the table of elements is a period.
• Hydrogen, the 1st element in Period 1, has 1 electron in
its 1st energy level.
• Lithium, the 1st element in Period 2, has 1 electron in its
2nd energy level.
• Pattern: Period # = one________in that # energy level
for the 1st column of the periodic table
5.1 Organizing the Elements
The Periodic Law
Groups
Each_________in the periodic table is called a group.
• similar electron configurations
• similar chemical properties
• This pattern of repeating properties is the ____________.
5.1 Organizing the Elements
The Periodic Law
Periodic Table of the Elements
5.1 Organizing the Elements
Atomic Mass
There are four pieces of information for each
element.
_________________
_________________
_________________
_________________
5.1 Organizing the Elements
Classes of Elements
• State:_______of symbol
– solid—black
– liquid—purple
– gas—red
• Occurrence in nature:
– Non-natural—_____symbol
• General properties:
________________________
– metal—blue
– nonmetal—yellow
– metalloid—green
5.1 Organizing the Elements
Classes of Elements
Metals
• Good________________of electric current and heat
• Except for mercury,_______at room temperature
• Most are _____________
• Many are ____________
• can be drawn into thin wires
5.1 Organizing the Elements
Classes of Elements
The metals in groups__through___are called transition
metals.
Transition metals: elements that form a bridge
between the elements on the left and right sides of the
periodic table.
• Examples: copper and silver
• Among the first elements discovered
• Ability to form compounds with distinctive____________
5.1 Organizing the Elements
Classes of Elements
A compound of oxygen and the transition element
erbium is used to tint the pink glass lenses.
5.1 Organizing the Elements
Classes of Elements
Nonmetals
Generally have properties opposite to metals’.
• Nonmetals:
– poor conductors of heat and electric current
– Low____________points
– many are___________at room temp
– Nonmetals that are solid at room temp tend to be
_____________
5.1 Organizing the Elements
Classes of Elements
Fluorine is the most reactive nonmetal. The gases
in Group 18 are the least reactive elements in the
table. Some toothpastes use a compound of the
nonmetal fluorine and the metal sodium to help
prevent tooth decay.
5.1 Organizing the Elements
Classes of Elements
Metalloids
 Between metals and nonmetals
• Metalloids: elements with properties that fall
between those of metals and nonmetals
• Examples:
• A metalloid’s ability to conduct electric current
varies with _____________________
• Silicon (Si) and germanium (Ge) are good
insulators at low temperatures and good
conductors at high temperatures.
5.1 Organizing the Elements
Variations Across a Period
Across a period from left to right, the
elements become less____________and more
_____________________in their properties
From left to right across Period 3, there are three
metals (Na, Mg, and Al), one metalloid (Si), and
four nonmetals (P, S, Cl, and Ar).
5.1 Organizing the Elements
Atomic Mass
Atomic mass depends on the distribution of an
element’s____________in nature and their masses
Atomic Mass Units
The mass of an atom in grams is extremely small.
• atomic mass unit (___): 1/12 the mass of a carbon-12 atom
5.1 Organizing the Elements
Atomic Mass
Isotopes
In nature, most elements exist as a________of two or
more isotopes.
Example: chlorine has an atomic mass of 35.453 amu.
• natural isotopes of chlorine: chlorine-35 & chlorine-37.
• An atom of chlorine-35 has 17 protons and 18 neutrons.
• An atom of chlorine-37 has 17 protons and 20 neutrons.
5.1 Organizing the Elements
Atomic Mass
_____________________________
1. Multiply the % abundance (relative abundance) in decimal
form by the atomic mass of each isotope
2. Add all values together to find the average atomic mass
Example: 0.7578(34.969) + 0.2422(36.966) = 35.453 amu
5.1 Organizing the Elements
Valence Electrons
Elements in a group have similar properties
because they have the same number of ________
electrons
Valence electron: an electron in the ___________
occupied energy level of an atom
5.1 Organizing the Elements
Valence Electrons
When the A groups in the periodic table are
numbered from 1 through 8, the group number
matches the number of valence electrons in the
electron configuration of an element in that group.
• Valence electrons play a key role in chemical
reactions.
• Properties vary across a period because the number
of valence electrons_____________from left to right.
5.1 Organizing the Elements
Valence Electrons
• Groups have similar properties because they
have the same number of valence electrons
– Properties aren’t identical because valence
electrons are in different _______________________
• Because hydrogen has a single valence electron, it
is grouped with other elements, such as lithium, that
have only one valence electron.
5.1 Organizing the Elements
The Alkali Metals
Alkali metals:
– 1 valence electron (group 1A)
– very ________________
– found in nature only in ________________
– reactivity ___________ from top to bottom (group)
5.1 Organizing the Elements
The Alkali Metals
Sodium reacts violently with water and releases
enough energy to ignite the hydrogen gas that is
produced.
Sodium and potassium are stored under oil to keep
them from reacting with the oxygen and water vapor
in air.
Cesium is so reactive that it is usually stored in a
sealed glass tube containing argon gas.
5.1 Organizing the Elements
The Alkali Metals
A Unlike most metals, the alkali metal sodium
is soft enough to cut with a knife.
B When sodium reacts with water, enough
energy is released to ignite the hydrogen that
is produced.
5.1 Organizing the Elements
The Alkaline Earth Metals
Alkaline earth metals:
– 2 valence electrons (group 2A)
– _____________than Group 1A
– different reactivity shown by reaction with______
• Calcium, strontium, and barium react easily with cold water.
• Magnesium will react with hot water but not cold water.
• No reaction occurs when beryllium is added to water.
5.1 Organizing the Elements
The Alkaline Earth Metals
Chlorophyll molecules in spinach contain
magnesium. An oyster shell and a pearl are both
made from calcium carbonate. A plaster cast
contains the compound calcium
sulfate.
Oyster shell with pearl
Spinach plant
Plaster cast
5.1 Organizing the Elements
The Boron Family
Group 3A contains the metalloid boron, the wellknown metal aluminum, and three less familiar metals
(gallium, indium, and thallium).
 3 valence electrons
5.1 Organizing the Elements
The Boron Family
A compound of boron,
silicon, and oxygen is used
to make glass that does not
shatter easily when its
temperature changes
rapidly. Glass that contains
boron is used to make
laboratory glassware and
cookware that can go
directly from the oven to the
refrigerator.
5.1 Organizing the Elements
The Carbon Family
Group 4A contains a nonmetal (carbon), two
metalloids (silicon and germanium), and two metals
(tin and lead).
• 4 valence electrons
• metallic nature_______________from top to bottom
– Germanium is a better conductor than silicon.
5.1 Organizing the Elements
The Carbon Family
Except for water, most of the compounds in your
body contain ________________.
Life on Earth would not exist without carbon.
Reactions that occur in the cells of your body are
controlled by carbon compounds.
5.1 Organizing the Elements
The Carbon Family
Silicon is the
second most
abundant element
in Earth’s crust. The
clay used to
produce this pottery
contains silicon
compounds called
silicates.
5.1 Organizing the Elements
The Nitrogen Family
Group 5A contains two nonmetals (nitrogen and
phosphorus), two metalloids (arsenic and
antimony), and one metal (bismuth).
• 5 valence electrons
• wide range of _______________properties
– Nitrogen is a nonmetal gas, phosphorus is a solid
nonmetal, and bismuth is a dense metal.
5.1 Organizing the Elements
The Nitrogen Family
When air is cooled, the oxygen condenses before
the nitrogen because nitrogen has a lower boiling
point than oxygen.
Much of the nitrogen obtained from air is used to
produce fertilizers.
Besides nitrogen, fertilizers often contain
phosphorus.
5.1 Organizing the Elements
The Nitrogen Family
The numbers on the bags of fertilizer are, from
left to right, the relative amounts of nitrogen,
phosphorus, and potassium.
5.1 Organizing the Elements
The Oxygen Family
Group 6A has three nonmetals (oxygen, sulfur,
and selenium), and two metalloids (tellurium and
polonium).
– 6 valence electrons
5.1 Organizing the Elements
The Oxygen Family
________is the most abundant element in Earth’s
crust.
Complex forms of life need oxygen to stay alive
because oxygen is used to release the energy
stored in food.
Ozone is another form of the element oxygen. At
upper levels of the atmosphere, ozone absorbs
harmful radiation emitted by the sun.
5.1 Organizing the Elements
The Oxygen Family
Sulfur was one of the first
elements to be discovered
because it is found in
large natural deposits.
5.1 Organizing the Elements
The Halogens
Group 7A
– 7 valence electrons
– chlorine=gas, bromine=liquid, iodine=solid (room temp)
5.1 Organizing the Elements
The Halogen Family
Despite their physical differences,
the halogens have similar
chemical properties.
Halogens react easily with most
metals. This photograph shows
chlorine reacting with steel wool.
5.1 Organizing the Elements
The Noble Gases
Group 8A
• Have___________valence energy levels
– Helium has 2 valence electrons
– Other noble gases have 8 valence electrons
– colorless and odorless
– extremely ____________________
5.1 Organizing the Elements
The Noble Gases
When electric current
passes through noble
gases, they emit
different colors. Helium
emits pink, neon emits
orange-red, argon emits
lavender, krypton emits
white, and xenon emits
blue.