Mr. Passman - 2008
4-1. INTRODUCTION TO THE PERIODIC TABLE
DEVELOPMENT OF THE PERIODIC TABLE.
According to Aristotle, an early Greek scientist, there were only four qualities of all earthly elements. Earth, Wind, Fire, and Air. A fifth element, called Ether was supposed to be in space. He did not believe in the theory of atoms. Everything on earth was composed of pairs of hot/cold and wet/dry opposites. They knew of the existence of certain substances, and were able to separate them from rocks. There were 8 metals; copper, gold, iron, lead, mercury, silver, tin, and zinc.Two non-metals; carbon and sulfur, and one substance that had some properties of both called antimony.
After the renaissance period (Da Vinci, Galileo) ended, scientists began to separate and identify new elements. By the end of the 1700’s, 20 new elements had been discovered and named. These included 14 metals; bismuth, phosphorus, cobalt, platinum, nickel, magnesium, manganese, chromium, molybdenum, tellurium, tungsten, uranium, zirconium, strontium, and titanium. One substance discovered, arsenic, had properties of both metals and nonmetals. But the most important discoveries of this period were the gases. Scientists discovered that air contained hydrogen, nitrogen, chlorine, and most importantly oxygen.
Antoine-Laurent Lavoisier, a French chemist, discovered a substance in 1774 he called oxygen permitted combustion (fire) to occur, and when it was used up, the flame went out. Prior to this discovery, everyone believed that burning was caused by a hypothetical substance called “phlogiston”. This substance was supposed to be part of every combustible material. When you burned something, phlogiston was driven off, with the deflogistonated substance left over. So wood was made up of ash and phlogiston. Unfortunately, Lavoisier was beheaded by the guillotine in the Reign of Terror during the French Revolution of 1789.
BY the mid-1800's,scientists had isolated 28 more elements, 24 of them metals; niobium, tantalum, cerium, iridium, osmium, palladium, rhenium, rhodium, potassium, sodium, barium, calcium, cadmium, lithium, selenium, aluminum, ruthenium, thorium, vanadium, francium, lanthanum, erbium, terbium, and cesium. Also found were 2 non-metals, iodine and bromine, and 2 having properties of both metals and non-metals, the elements boron and silicon. This gave them knowledge of 63 different elements.
SCIENTISTS
The rectangular periodic table is familiar to us because it is on the walls of most science classrooms. This ingenious functional grouping of the chemical elements was created by several European scientists in the decade of the 1860's. In 1863, a French geologist, A. E. Béguyer de Chancourtois created a list of the elements arranged by increasing atomic weight. The list was wrapped around a cylinder so that several sets of similar elements lined up, creating the first geometric representation of the periodic law.
In England, chemist John A. R. Newlands was also wrapping the elements, noting that chemical groups repeated every eight elements. He named this the octave rule, and compared it to a musical scale. Some less observant members of the English Chemical Society considered this absurd, so his work was ignored for years.
Chemists Dmitrii I. Mendeleev, a Russian, and German Lothar Meyer were working independently in 1868 and 1869 on the arrangement of elements into seven columns, corresponding to various chemical and physical properties. Their tables were similar - they acknowledged each other's work - the differences are subtle but important: Meyer's table was an accurate (for the time) accounting of the known facts about each element, such as melting point and atomic volume. The table clearly showed the existence of periodic chemical families. Meyer’s table was published in 1870.
A year earlier however, Mendeleev presented a much bolder and scientifically useful table. His paper, On the Relation of the Properties to the Atomic Weights of the Elements, was enthusiastically received by the Russian Chemical Society. In Mendeleev’s table, the periodic relationship between chemical groups, that is, elements with similar chemical reactions, is clearly illustrated. In a scientific triumph, gaps in the table accurately predicted undiscovered elements.
He placed all of the information known about each element on separate cards. When Mendeleev arranged the cards in order of increasing atomic mass, he found that the valence numbers occurred in a pattern.
When he arranged the elements in rows of 7 columns, he observed that all elements in the same column had similar properties. He also discovered that the valence numbers occurred in the pattern 1 2 3 4 3 2 1.His original table can be found at
He designed a table in which elements were arranged in the order of increasing atomic mass, and he left spaces for elements that were not yet known. Mendeleev provided for variance from strict atomic weight order, left space for new elements, and predicted three yet-to-be-discovered elements including technetium, scandium, and germanium. His table did not include any of the Noble Gases, however, which had not yet been discovered.
Although it is over 130 years old, Mendeleev's table differs little from the charts on the walls of laboratories today. The insight obtained in that productive decade resulted in a tool that furthers understanding and eases the use of chemistry in every laboratory in the world.
Henry Moseley was a British chemist who studied under Rutherford and developed the application of X-ray spectra to study atomic structure; his discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers. Tragically for the development of science, Moseley was killed in action at Gallipoli in 1915.
In 1913, almost fifty years after Mendeleev, Henry Moseley published the results of his measurements of the wavelengths of the X-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the X-ray emissions of the elements coincided with the ordering of the elements by atomic number. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant item in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number.
When Moseley rearranged the elements according to increasing atomic number, the few problems with Mendeleev's periodic table had disappeared. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements, not atomic mass, and has an 8th column, for the noble gases, which were not known to exist at Mendeleev’s time.
Today's table consists of 113 elements. The horizontal rows are called periods, and they show the changes in properties of the elements that result from different number of valence electrons.
The vertical columns are called groups or families, and show similarities in properties of the elements that result from having the same number of valence electrons.
A wide variety of information is available about each element in the periodic table from the chart.
Most elements are solids, 2 are liquids, and 11 are gases.
Families of elements are classified as metals, non-metals, and metalloids. The dark stairstep line separates the metals from the non-metals, with elements called metalloids along this line.
Most of the elements are metals. Some of their characteristics are:
GOOD CONDUCTORS OF HEAT
GOOD CONDUCTORS OF ELECTRICITY
SHINY
CAN BE DRAWN INTO THIN WIRES
CAN BE HAMMERED EASILY INTO DIFFERENT SHAPES
HIGH MELTING POINTS
GIVE UP ELECTRONS WHEN BONDING TO FORM COMPOUNDS
FORM POSITIVE IONS
Non-metal characteristics include:
POOR CONDUCTORS OF HEAT
POOR CONDUCTORS OF ELECTRICITY
DULL
BRITTLE AND TEND TO BREAK RATHER THAN BEND
LOW MELTING POINTS
ACCEPT ELECTRONS WHEN BONDING TO FORM COMPOUNDS
FORM NEGATIVE IONS
There is a small group of elements around the stairstep line that have the characteristics of both metals and non-metals. These are called metalloids.
Metalloid characteristics include:
MEDIUM CONDUCTORS OF ELECTRICITY
SHINY OR DULL
CHEMICAL SYMBOLS
For many years, scientists had to spell out the names of the elements when writing about them, or use pictorial symbols for them. In 1813, a system was developed to help scientists speed up their work.
Chemical symbols are a shorthand way of representing the elements. Each symbol (except for elements above element 109) consists of one or two letters, usually taken from the element's name. In most cases, the names were assigned by the scientist discovering the element.
The rule is that the first letter is always capitalized, and the second letter, if any, is always written in lower case.
Sometimes, the shorthand name is not similar to the name of the element. This is because the scientists sometimes used Old Latin and Greek names for these elements.
Examples are
GOLDAuAURUM
LEADPbPLUMBUM
IRONFeFERRUM
MERCURYHgHYDRAGYRUM
SODIUMNaNATRIUM
POTASSIUMKKALIUM
COPPERCuCUPRUM
SILVERAgARGENTUM
TINSnSTANNUM
ANTIMONYSbSTIBIUM
TUNGSTENWWOLFRAM
ELEMENT NAMES
The discoverers of an element have the privilege of naming it. Most have Latin or Greek names. They can be named for people, colors, countries, cities, states, features, planets, and asteroids as examples.
Look through the names and meanings of the elements on the ELEMENTS CHART.
HOW TO READ THE PERIODIC CHART
There are a number of things to be learned about any element from the Periodic Chart.
A.TOP NUMBER
The top number is the Atomic Number.
It is also the number of protons and electrons in a neutral atom
B.BOTTOM NUMBER
The bottom number is the Atomic Mass.
When it is rounded to the nearest whole number, and the top number is subtracted from it, it is the average number of neutrons in an atom of that element.
C.NUMBER OF SHELLS
No matter where an element is on the periodic table, counting down the rows will tell how many rings or shells are in the element
ROW 1up to 2 electrons
ROW 2up to 8 electrons in outer ring, up to 10 electrons total address 2-8
ROW 3up to 8 electrons in outer ring, up to 18 electrons total address 2-8-8
ROW 4up to 8 electrons in outer ring, up to 36 electrons total address 2-8-18-8
ROW 5up to 8 electrons in outer ring, up to 54 electrons total address 2-8-18-18-8
ROW 6up to 8 electrons in outer ring, up to 86 electrons total address 2-8-18-32-18-8
ROW 7up to 2 electrons in outer ring, up to 109 electrons total address 2-8-18-32-32-12-2
D.VALENCE ELECTRONS
Use the numbers above the chart to figure out how many valence electrons there are. If it is a number below 4, the element will lose electrons, and become a positive ion. An element with 4 can go either way.If it is a number between 5 and 7, it will gain them, and become a negative ion.If it has 8, it will not want to do anything.
COLUMNION CHARGE
1Loses 1 electron+1
2Loses 2 electrons+2
3-12Most lose 2 +2
except elements 24, 41-45, 47, 79+1
and element 46 0
13Loses 3 electrons+3
14Can lose or gain 4 electrons+/-4
15Gains 3 electrons-3
16Gains 2 electrons-2
17Gains 1 electron-1
18Does not want any more 0
4-2. REPRESENTATIVE ELEMENTS OF THE CHEMICAL FAMILIES
GROUP 1
Contains the most active metals and are called the ALKALI METALS. They have 1 electron in their outer valence ring and want to give it up very easily. They are never found as free elements in nature. They are always found in compounds. They react very violently with water, increasing in activity from lithium through francium. When refined, they are silvery solids with low densities and low melting points.The ALKALI METALS combine easily with the HALOGEN FAMILY in group 17 to form salts.Hydrogen, sodium and potassium are important elements for life
GROUP 2
These metals are not quite as active as those in group 1. They are called the ALKALINE EARTH METALS. They have 2 electrons in the outer valence ring and want to give them up. They are never found as free elements in nature, they are always found in compounds. Each alkaline earth metal is denser and harder and has a higher melting point than the alkali metal in the same period. The ALKALINE EARTH METALS combine easily with the HALOGEN FAMILY in group 17 to form salts. Calcium and magnesium are important elements for life.
FROM METALS TO NON-METALS
GROUP 13
This group is called the BORON FAMILY. They have 3 valence electrons. Only Boron is a metalloid.The rest of the group is made up of the metals aluminum, gallium, indium, and thallium.
GROUP 14
This group is called the CARBON FAMILY. All have 4 valence electrons. Carbon is a non-metal, silicon and germanium are metalloids, while tin and lead are metals. Carbon can form millions of combinations, and is the basis of all life forms on Earth.
The metalloids silicon and germanium are used to manufacture semiconductors, which are the heart of the integrated circuits used computers, CD players and many other devices.
GROUP 15
This group is called the NITROGEN FAMILY. They all have 5 valence electrons, so they need to add 3 electrons. They tend to share electrons when they bond and they form negative ions.
Nitrogen is a gas, phosphorus is a non-metal, arsenic and antimony are metalloids, and bismuth is a metal. Nitrogen and phosphorous are part of DNA in every living organism, and are important elements for life.
GROUP 16
This group is called the OXYGEN FAMILY. They have 6 valence electrons, and they need to add 2 valence electrons. They tend to share electrons when they bond and they form negative ions. Oxygen is a very reactive gas, and is never found as an individual atom. It combines with almost every other element to form compounds. Sulfur is a yellow solid, while selenium conducts electricity and is used in solar cells. Tellurium and polonium are metalloids. Oxygen is an important element for life, while selenium is also required in trace amounts.
GROUP 17
This group is called the HALOGEN FAMILY. They have 7 valence electrons, and want to add 1 more electron. Fluorine and chlorine are both gases, while bromine is a brown liquid. Iodine is a solid, black solid, while astatine is a metalloid. All of these form both covalent and ionic bonds, and they form negative ions. Fluorine and chlorine are very active elements, and are never found in nature in the free state.The HALOGEN FAMILY ELEMENTS combine easily with the ALKALI METALS and the ALKALINE EARTH METALS in groups 1 and 2 to form salts.
GROUP 18
This group is called the NOBLE GASES FAMILY. The outer ring is filled. Helium has 2 electrons, all the rest have 8 electrons, so they are extremely unreactive. All of the elements in this group, helium, neon, argon, krypton, xenon, and radon, are gases. The NOBLE GASES were once called “inert elements” because of their lack of reaction with other elements
4-3 TRANSITION ELEMENTS
GROUPS 3-12
These are called TRANSITION METALS. They have properties similar to one another, but different that the properties of the other families. Most occur are compounds, and are brightly colored.Almost all of them have two valence electrons. A few have 1 valence electron, and one has no outer ring electrons. When they combine with other atoms, they can lose their valence electrons, and also lose electrons from the next energy level, or even share electrons. This sharing of electrons is what enables metals to conduct electricity through a process called metallic bonding.
THE IRON TRIAD
Three elements, iron, cobalt, and nickel, have such similar properties that they are known as the iron triad. These are the only elements that have magnetic properties.
Iron is an important element for life since it carries the oxygen as a part of the red blood cells to all other cells in many living things.
THE COINAGE METALS
Gold, silver, and copper were used for coins for thousands of years, although they are no longer used for this purpose, but are used for jewelry.
THE PLATINUM GROUP
Ruthenium, rhodium, palladium, osmium, iridium, and platinum are sometimes called the platinum group because they have similar properties. They don not combine easily with other elements.
INNER TRANSITION ELEMENTS
There are two groups of 14 elements that are normally shown below the rest of the periodic table. This is because if they were put in their correct place, the table would be much wider than it is normally.
The first row of these elements (58-71) is called the LANTHANIDE series. These are soft metals that are hard to distinguish from one another.The members of the lanthanide series are found naturally.
The second row of these elements (90-103) is called the ACTINIDE series. All of these are radioactive elements. With the exception of thorium, protactinium, and uranium, none of these elements are found in nature today. They are all created artificially in the laboratory, and all have very short half-lives. Uranium has a half-life of 4.5 billion years, so it decays very slowly.
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