17.3: The Periodic Table

Traditionally, early Greeks considered that there were four classical elements: earth, air, fire, and water.

Some Early Ideas About Elements

Later, around 1667, it was thought there was the existence of, in addition to the classical four elements of the Greeks, an additional fire-like element called “phlogiston” that was contained within combustible (burnable) or rustable bodies, and released during combustion or rusting .

The theory was an attempt to explain oxidation processes such as combustion and the rusting of metals.

Some Early Ideas About Elements

The phlogiston theory from 1667 viewed phlogiston as a component of matter.

The burning or rusting of a material was considered to be the escaping of phlogiston from the matter.

If a material did not burn or rust, it was considered to contain no phlogiston.

What the heck is “phlogiston?”

In the late 1700s, Antoine Lavoisier of France suggested that burning was actually a chemical combination with oxygen.

Lavoisier realized that there needed to be a new concept of elements, compounds, and chemical change.

Discovery of Modern Elements

What we now know . . . at least, for now.

We now know that there are 89 naturally-occurring elements and at least 23 short-lived and artificially prepared elements.

The elements of the periodic table are believed to be all the elements that exist in the universe! Click here to see how we know:

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The first 103 elements have internationally accepted names, which can come from: an unusual or identifying property of the

element. places, cities, and countries. famous scientists. Greek mythology. Astronomical objects.

Naming the Elements

The elements of aluminum, Iron, Oxygen, and Silicon make up about 88 percent of the earth's solid surface.

Water on the surface and in the air as clouds and fog is made up of hydrogen and oxygen.

The air is 99 percent nitrogen and oxygen.

Hydrogen, oxygen, and carbon make up 97 percent of a person.

Thus almost everything you see in this picture is made up of just seven elements.

Dmitri Mendeleev was born in 1834 in Siberia, the youngest of 14 children, and he died in 1907.

He gave us a functional scheme with which to classify elements.

Along Came Mendeleev . . .

Dmitri Mendeleev: Father of the Periodic Table

HOW HIS WORKED… Put elements in rows by increasing atomic mass.

Put elements in columns by the way they reacted.

He was able to predict properties of undiscovered elements.

SOME PROBLEMS… He had to leave blank spaces for what he

said were undiscovered elements. (Turned out he was right!)

He broke the pattern of increasing atomic weight to keep similar reacting elements together.

Mendeleev’s Periodic Table

Scientists have since discovered the missing elements and found that their properties were close to what Mendeleev had predicted.

On March 6, 1869, he presented his periodic table to the scientific community.

Improvements Mendeleev wasn’t too far off. In 1913, Henry Moseley of England put elements in rows by increasing ATOMIC NUMBER instead of increasing atomic mass!! If you look at cobalt and nickel, even though cobalt has fewer protons, its average atomic mass is greater than nickel’s.

Seaborgium and bohrium are the same way.

Groups or Families Groups are columns of the periodic table. Columns are vertical, like columns that

hold up a porch roof. Elements in the same group have similar

chemical and physical properties!! (Mendeleev did that on purpose.)

Families have the same number of valence electrons.

They will form the same kinds of ions (charged particles) and react similarly.

Valence electrons are the electrons in the outside energy level of an atom.

ValenceElectrons

ValenceElectrons

http://www.chemicalelements.com/index.html

They are responsible for the bonding of one atom to another.

Families on the Periodic Table Families may be one column, or several columns put together.

Families often have names rather than numbers (just like some families have a common last name).

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Another way to draw an atom model is with an electron dot diagram, or Lewis Structure.

They simply use the symbol of the element and the number of valence electrons that element has.

All atoms become stable when they bond with another so that their outside energy level becomes stable.

They become stable when they have eight valence electrons in their outside energy level.

Elements generally stop bonding with others when they have eight electrons in the outermost energy level. This is called the “Rule of Octet.”

Electron Dot Diagrams

Rows are also called periods, and they are horizontal.

The row an element is in tells you how many energy levels it has.

There are up to 7 energy levels.

Rows on the Periodic Table

Forming Ions

Sodium (Na ) Chlorine (Cl )-+

Using Dot Diagrams to Show Bonding

Cl

• Sodium has one valence electron.• Chlorine has 7 valence electrons.• When they bond, you can see how chlorine

now has a stable outer shell.• You also know sodium is now stable since it

got rid of its single valence electron.

[Na]+ [ Cl ]- Na

Elements on the upper right side of the periodic table—AND hydrogen—are nonmetals.

Elements on the left hand side—EXCEPT hydrogen—are metals. That includes the rows at the very

bottom. A zigzag line separates the metals from the nonmetals.

Many of the elements touching the zigzag line are called metalloids.

Regions on the Table

Hydrogen is the most abundant element in the universe.

Hydrogen, along with helium, form the building blocks of the larger elements.

The largest of the elements (the ones with the most protons) are believed to be formed in supernovas and flung out into space.

Supernovas are stars that explode with a great deal of heat and energy.

Elements with an atomic number above 92, AND Pm (61), and Tc (43) are rare or nonexistent on Earth.

They have been detected using a telescope with a spectrometer.

Elements in the Universe

Visible Spectra of Known Elements