The Periodic Table
Study it like the cool kids…
Physical Science – SS -- 10/21/15
What do you already know about the
periodic table?
BONUS: What do you want to know about the
Periodic Table?
(Go and write it on the GIANT PostIt on the
cabinet.)
The Search for Order
Until 1750, scientists had
identified only 17 elements,
mainly metals, such as copper
and iron.
More discovered and the need
to order them increased.
FIRST ATTEMPT: In 1789,
Antoine Lavoisier grouped the
known elements into
categories he called metals,
nonmetals, gases, and earths.
Mendeleev’s Periodic Table
How did Mendeleev
organize the
elements in his
periodic table?
Periodic Table Lab: Have a go at it!
• Answer the pre-lab questions
– come show Mr. Hill to get the cards
• Use the card to do as Mendeleev did…
• Get the rest of the cards
• Answer the post-questions with your group
• HW – Answer the extension questions
– Mendeleev: SciShow
Mendeleev’s Periodic Table
Periods
Mendeleev arranged the elements into rows in
order of increasing mass so that elements with
similar properties were in the same column.
Groups
Mendeleev’s Periodic Table
Mendeleev’s Proposal
In the 1860s, Dmitri
Mendeleev developed an
approach for organizing the
elements while playing the
card game solitaire.
Mendeleev’s Periodic Table
Mendeleev made a “deck of cards” of the elements, listing an element’s name,
mass, and properties on each card. When Mendeleev lined up the cards in order of
increasing mass, a pattern emerged. The key was to break the elements into rows.
Mendeleev’s Periodic Table
The final arrangement was similar to a winning
arrangement in solitaire, except that the columns were
organized by properties instead of suits. Within a column,
the masses increased from top to bottom.
Mendeleev’s chart was a periodic table.
A periodic table is an arrangement of elements in
columns, based on a set of properties that repeat from
row to row.
Mendeleev’s Periodic Table
Evidence Supporting Mendeleev’s Table
What evidence helped verify the usefulness of
Mendeleev’s table?
Mendeleev’s Periodic Table
Mendeleev’s Prediction
Gaps in the table!
Mendeleev was able to predict the properties of
an element based on its location in his table.
He used the properties of elements located near
the blank spaces in his table to predict properties
for undiscovered elements.
Mendeleev’s Periodic Table
The close match between Mendeleev’s predictions
and the actual properties of new elements showed
how useful his periodic table could be.
Mendeleev’s Periodic Table – Example of Predictability
Mendeleev named missing elements after
elements in the same group.
He gave the name “eka-aluminum” to the missing
element one space below aluminum in the table.
Mendeleev predicted that “eka-aluminum” would
• be a soft metal,
• have a low melting point, and
• have a density of 5.9 g/cm3.
Mendeleev’s Periodic Table - Example of Predictability
In 1875, a French chemist discovered a new
element.
He named the element gallium (Ga) in honor of
France. (The Latin name for France is Gallia.)
Gallium
• is a soft metal,
• has a melting point of 29.7°C, and
• has a density of 5.91 g/cm3.
Mendeleev’s Periodic Table…Gallium randomness
Heat from a person's hand can melt gallium.
In some traffic signals, there are tiny light
emitting diodes (LEDs) that contain a compound
of gallium.
Mendeleev’s Periodic Table
Scientists use the periodic table to explain the
chemical behavior of different groups of elements.
• The discovery of scandium (Sc) in 1879
• The discovery of germanium (Ge) in 1886
= More evidence.
Assessment Questions
1. In Mendeleev’s periodic table, elements with similar
properties were grouped
a.
b.
c.
d.
in the same row.
in the same column.
in diagonal lines that run from top left to the bottom right.
in pairs of two.
Assessment Questions
1. In Mendeleev’s periodic table, elements with similar
properties were grouped
a.
b.
c.
d.
in the same row.
in the same column.
in diagonal lines that run from top left to the bottom right.
in pairs of two.
ANS:
B
Assessment Questions
2. For which element did Mendeleev correctly predict the
properties even before it had been discovered?
a.
b.
c.
d.
gallium
hydrogen
bromine
aluminum
Assessment Questions
2. For which element did Mendeleev correctly predict the
properties even before it had been discovered?
a.
b.
c.
d.
gallium
hydrogen
bromine
aluminum
ANS:
A
5.2
Take the Tour!
Take the Tour!
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.
The Periodic Law
CrashCourse
How is the modern periodic table organized?
The Periodic Law
How is the modern periodic table organized?
In the modern periodic table, elements are
arranged by increasing atomic number (number of
protons).
The Periodic Law
How is the modern periodic table organized?
In the modern periodic table, elements are
arranged by increasing atomic number (number of
protons).
Properties of elements repeat in a predictable way
when atomic numbers are used to arrange
elements into groups.
The Periodic Law
The modern periodic table is based on atomic number,
or number of protons.
The Periodic Law
Periods
Each row in the table of elements is a period.
• Hydrogen, the first element in Period 1, has one
electron in its first energy level.
• Lithium, the first element in Period 2, has one
electron in its second energy level.
• Sodium, the first element in Period 3, has one
electron in its third energy level.
• This pattern applies to all the elements in the first
column on the table.
The Periodic Law
Groups
Each column in the periodic table is called a
group.
• The elements in a group have similar electron
configurations, so members of a group in the
periodic table have similar chemical properties.
• This pattern of repeating properties is the periodic
law.
The Periodic Law
Periodic Table of the Elements
Atomic Mass
What does the atomic mass of an element depend
on?
Atomic mass is a value that depends on the
distribution of an element’s isotopes in nature and
the masses of those isotopes.
Atomic Mass
Atomic Mass Units
The mass of an atom in grams is extremely small.
In order to have a convenient way to compare the
masses of atoms, scientists chose one isotope to
serve as a standard.
• Scientists assigned 12 atomic mass units to the
carbon-12 atom, which has 6 protons and 6
neutrons.
• An atomic mass unit (amu) is defined as one
twelfth the mass of a carbon-12 atom.
Atomic Mass
There are four pieces of information for each element.
Atomic Mass
There are four pieces of information for each element.
Atomic number
Atomic Mass
There are four pieces of information for each element.
Atomic number
Element symbol
Atomic Mass
There are four pieces of information for each element.
Atomic number
Element symbol
Element name
Atomic Mass
There are four pieces of information for each element.
Atomic number
Element symbol
Element name
Atomic mass
Atomic Mass
Isotopes of Chlorine
In nature, most elements exist as a mixture of
two or more isotopes. The element chlorine has
an atomic mass of 35.453 amu. Where does the
number 35.453 come from?
• There are two natural isotopes of chlorine, chlorine35 and chlorine-37.
• An atom of chlorine-35 has 17 protons and 18
neutrons.
• An atom of chlorine-37 has 17 protons and 20
neutrons.
Atomic Mass
Weighted Averages
This table shows the atomic masses for the two naturally
occurring chlorine isotopes. The value of the atomic mass
for chlorine is a weighted average. If you add the atomic
masses of the isotopes and divide by 2, you get 35.967,
not 35.453.
Classes of Elements
What categories are used to classify elements on
the periodic table?
Classes of Elements
Elements are classified as metals, nonmetals, and
metalloids.
Classifying Elements
Three different ways to classify elements in the P-Table
1. State: solid—black symbol, liquid—purple symbol, or
gas—red symbol
2. Occurrence in nature: elements that do not occur
naturally—
symbol.
3. General properties: metal—blue background, nonmetal—
yellow background, or metalloid—green background
Metals
Most common type
Metals are elements that are good conductors of electric
current and heat.
• Except for mercury, metals are solids at room
temperature.
• Most metals are malleable.
• Many metals are ductile; that is, they can be drawn
into thin wires.
Classes of Elements
The metals in groups 3 through 12 are called transition
metals. Transition metals are elements that form a
bridge between the elements on the left and right sides
of the table.
• Transition elements, such as copper and silver, were among
the first elements discovered.
• One property of many transition metals is their ability to
form compounds with distinctive colors.
RANDOM SIDE NOTE
ERBIUM + Oxygen
A compound used to tint the pink glass lenses.
Elton John’s Dog
Classes of Elements
Nonmetals
Nonmetals generally have properties opposite to
those of metals.
• Nonmetals are elements that are poor conductors
of heat and electric current.
• Nonmetals have low boiling points–many nonmetals
are gases at room temperature.
• Nonmetals that are solids at room temperature
tend to be brittle. If they are hit with a hammer,
they shatter or crumble.
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.
Classes of Elements
Metalloids
Metalloid elements are located on the periodic table
between metals and nonmetals.
• Metalloids are elements with properties that fall
between those of metals and nonmetals.
• For example, a metalloid’s ability to conduct electric
current varies with temperature. Silicon (Si) and
germanium (Ge) are good insulators at low
temperatures and good conductors at high
temperatures.
Variations Across a Period
How do properties vary across a period in the
periodic table?
Variations Across a Period
Across a period from left to right, the elements
become less metallic and more nonmetallic in their
properties.
Variations Across a Period
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).
Variations Across a Period
• Sodium reacts violently with water.
• Magnesium will not react with water unless the water
is hot.
• Aluminum does not react with water, but it does react
with oxygen.
• Silicon is generally unreactive.
• Phosphorus and sulfur do not react with water, but
they do react with oxygen.
• Chlorine is highly reactive.
• Argon hardly reacts at all.
Assessment Questions
1. What determines the atomic mass of an element?
a. the natural distribution of isotopes and the atomic numbers
of those isotopes
b. the natural distribution of isotopes and the masses of those
isotopes
c. the mass of the isotope of the element that has the most
neutrons
d. the average number of protons in the element’s nucleus
Assessment Questions
1. What determines the atomic mass of an element?
a. the natural distribution of isotopes and the atomic numbers
of those isotopes
b. the natural distribution of isotopes and the masses of those
isotopes
c. the mass of the isotope of the element that has the most
neutrons
d. the average number of protons in the element’s nucleus
ANS:
B
Assessment Questions
2. Which of the following is not characteristic of metals?
a.
b.
c.
d.
ductile
good electrical conductor
typically solid at room temperature
brittle
Assessment Questions
2. Which of the following is not characteristic of metals?
a.
b.
c.
d.
ductile
good electrical conductor
typically solid at room temperature
brittle
ANS:
D
Assessment Questions
3. Within a period of the periodic table, how do the
properties of the elements vary?
a.
b.
c.
d.
Metallic characteristics increase from left to right.
Metallic characteristics decrease from left to right.
Reactivity increases from left to right.
Reactivity decreases from left to right.
Assessment Questions
3. Within a period of the periodic table, how do the
properties of the elements vary?
a.
b.
c.
d.
Metallic characteristics increase from left to right.
Metallic characteristics decrease from left to right.
Reactivity increases from left to right.
Reactivity decreases from left to right.
ANS:
B
Assessment Questions
1. In the modern periodic table, elements are arranged in
order of increasing atomic mass.
True
False
Assessment Questions
1. In the modern periodic table, elements are arranged in
order of increasing atomic mass.
True
False
ANS:
F, atomic number