# Organizing the Elements

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Organizing the Elements

History of the Periodic Table
1860’s a Russian Scientist named Dmitri Mendeleev discovered a system for organizing all of the known elements. To help him find a pattern he put all of the known information on individual cards. He listed the elements known properties.

Individual Properties Listed
Known properties were: melting point, density, color, atomic mass, # of chemical bonds an element can form. Atomic mass is the average mass of one atom of that element.

Mendeleev’s Periodic Table
Patterns appeared when elements were arranged in order of increasing atomic mass. However, this did not always produce similar groups. So he moved the cards into the group it best fit. This left blank spaces on the table.

Mendeleev’s Periodic Table

Mendeleev’s Periodic Table
Mendeleev predicted that that the blank spaces would be filled by elements that had not yet been discovered. He even predicted the properties of new elements. Published his table in 1869 the new elements were discovered within 16 years.

Periodic – means regular, repeated pattern.
Modern Periodic Table Periodic – means regular, repeated pattern.

Modern Periodic Table Properties are repeated in each period or row of the table. Elements are arranged by increasing atomic number – not mass as Mendeleev had previously thought.

26 Fe Iron 55.847 - atomic number - elements symbol -elements name Atomic mass

Organization of the Table
An elements properties can be predicted from its location on the table. Across the row or down a column the elements’ properties change in a predictable way.

Groups or Families Elements in a column.
Numbered 1 on left to 18 on right. Elements in a group have similar characteristics. They have the same number of valence electrons.

Periods or Rows Contains a series of elements from different families.
The elements have very different properties. 7 periods of elements. 7 electron shells

Why it works The table works because it is based on the structure of atoms, especially the valence electrons. Atomic # increases by 1, so it has 1 more valence electron than the previous family. Atomic # increasing by 1 means it has one more proton than the previous atom.

Metals

Metals Found on the left of the zig-zag line.
Metals based on physical properties of hardness, shininess, malleability, ductility.

Physical Properties of metals
Malleability means that it can be pounded into shapes.

Physical Properties of metals
Ductility means that the metal can be pulled out or drawn into a long wire.

Physical Properties of metals
Conductors – most metals can transmit heat and electricity easily. Magnetic – several metals can be made into magnets or are attracted to magnets.

Chemical Properties of Metals
Some very reactive – sometimes explosive others not reactive at all. Metals on the left of the table Family 1 are the most reactive and they become less and less as you move right.

Alloys Mixture of metal.
Useful alloys combine the best properties of two or more metals into a single substance.

Metals in the Periodic Table
Alkali Family 1 Alkaline Earth Family 2 Transition Metals Families 3 -12 Mixed Groups Lanthinide Actinide

Alkali Metals Most reactive metals
Never found alone in nature, always in a compound. Soft, shiny, Sodium is an example. Why are they so reactive? Because they have one valence electron that they can easily give away.

Alkaline Earth Metals Group 2
Not as reactive as Group 1 but more reactive than most metals. Hard, bright white, good conductors of electricity. Each has 2 valence electrons which they easily lose.

Transition Metals Group 3 – 12
Form a bridge between the very reactive metals on the left side and the less reactive metals on the right. Very similar so that it is difficult to detect differences from one column to the next.

Transition Metals Fairly stable, reacting slowly or not at all with air and water. Used to make colorful paints such as cobalt blue.

Iron, Cobalt, Nickel First elements in groups 8,9, 10 called the iron triad. The only ones known to create a magnetic field.

Metals in Mixed Groups Groups 13 – 16 include: metals, nonmetals, metalloids. The metals to the right of the transition metals are not as reactive as Groups 1 &2.

Lanthanides & Actinides
Bottom of the periodic table are the Lanthanides, in the top row, and the Actinides in the bottom row. Called Rare Earth Elements Placed in periods 6 & 7 between the alkaline earth metals and the transition metals.

Lanthanides Soft, Malleable, shiny metals with high conductivity.

Actinides Only thorium and Uranium exist on Earth in any significant amounts. Uranium is used to produce energy in nuclear power plants. All elements after Uranium on the table were created artificially in a laboratory.

Bonding in Metals Most have 1-3 valance electrons which they lose easily. Usually lose the electron to a nonmetal and form ionic bonds. Sometimes metallic bonding occurs – the positively charged ions are surrounded by a sea of electrons. The electrons can slide past each other . This is how they are malleable, ductile, and good conductors of electricity. Page 331.

For example, during the reaction of sodium with chlorine:
sodium (on the left) loses its one valence electron to chlorine (on the right),    resulting in                             a positively charged sodium ion (left) and a negatively charged chlorine ion (right). The reaction of sodium with chlorine Concept simulation - Reenacts the reaction of sodium with chlorine. (Flash required)

Metal Facts Aluminum most abundant metal in the Earth’s crust.
Iron second most abundant. Metals must be dug or mined from earth’s crust. Iron is most widely used metal (steel), cobalt is sometimes used in steel. Nickel gives it the shiny color.

Nonmetals and Metalloids
Where are they located on the periodic table? What are the properties of nonmetals and metalloids?

What is a Nonmetal? 17 Nonmetals located to the right of the zig-zag line on the periodic table. Physical properties are the opposite of metals.

Physical Properties Dull, brittle, low densities, poor conductors of heat and electricity. Many non metals are gases at room Temperature which means they have low boiling points.

Chemical Properties Most nonmetals form compounds. They gain or share electrons. Family – Group 18 do not. This is because they have 8 valence electrons in their outermost energy level.

Compounds of Nonmetals
When nonmetals and metals react the valence electron moves from the metal to the nonmetal.

Compounds of Nonmetals
Nonmetals can also form compounds with other nonmetals. Atoms share electrons and become bonded together. Molecules that contain only 2 atoms are called diatomic molecules. (oxygen, nitrogen, hydrogen)

Attracting Electrons Most nonmetals form both ionic and covalent compounds. When a nonmetal gains electrons from metals the nonmetals become negative ions in ionic compounds

Bonding with other nonmetals
Atoms of nonmetals share electrons to form covalent compounds. NH3

Covalent Bond The idea of covalent bonding can be traced to Gilbert N. Lewis, who in 1916 described the sharing of electron pairs between atoms.

Group 18 is the only family that consists of all nonmetals.
First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 8 Families of Nonmetals Atomic Structure Group 18 is the only family that consists of all nonmetals.

Carbon Family 4 valence electrons Carbon is the only nonmetal.
All living things contain compounds that are made of carbon atoms.

Nitrogen Family Group 15 – 5 valence electrons
Atmosphere is 80 % nitrogen.

Oxygen Family Group 16, 6 valence electrons.
Usually gain or share 2 valence electrons. Oxygen is a diatomic molecule Oxygen is very reactive – it can combine with nearly all elements. Most abundant element in the Earth’s crust, 2nd most abundant in the atmosphere.

Halogen Family Group 17 contains fluorine, chlorine, bromine, iodine, astatine. 7 valence electrons, gains or shares one valence electrons when it reacts.

Noble Gases Group 18, do not mix with others.
Do not gain, share, lose electrons. Chemically stable because they have a full outer energy level.

Hydrogen Alone in the upper left corner.
Simplest element – usually its atoms contain one proton and one electron. Hydrogen is rarely found on Earth as an element. Usually combined with oxygen as water.

Metalloids On the border between metals and nonmetals.
Have characteristics of metals and nonmetals Most useful property is the varying ability to conduct electricity.. Used to make semiconductors which are substances that under some conditions can carry electricity like a metal, while other conditions cannot carry electricity like a nonmetal. Used to make computer chips.