Hillcrest Science Investigations

Study Sheet for quiz on December 8 th Coop A

H.S. 505
James Sylvester RN
Hillcrest High School
160-05 Highland Avenue
JAMAICA ESTATES, NY 11432
Phone: (718) 658-5407 Fax: (718) 739-5137


Periodic Table first discovered in 1869 by Dmitry I. Mendeleyev is a way of presenting all the elements so as to show their similarities and differences. The elements are arranged in increasing order of atomic number(Z) as you go from left to right accross the table. The horizontal rows a called periods and the vertical rows, groups.A noble gas is found at the right hand side of each period. There is a progression from metals to non-metals across each period. Elements found in groups (e.g. alkali, halogens) have a similar electronic configuration. The number of electrons in outer shell is the same as the number of the group (e.g. lithium 2·1).The block of elements between groups II and III are called transition metals. These are similar in many ways; they produce colored compounds, have variable valency and are often used as catalysts. Elements 58 to 71 are known as lanthanide or rare earth elements. These elements are found on earth in only very small amounts.Elements 90 to 103 are known as the actinide elements. They include most of the will known elements which are found in nuclear reactions. The elements with larger atomic numbers than 92 do not occur naturally. They have all been produced artificially by bombarding other elements with particles.

FAMILIES OF ELEMENTS With so many elements, it is impractical to being a study of each one individually. The elements here will first be classified generally as metals and nonmetals. Metals will be further divided into alkali and alkaline earth metals. Metalloids will be discussed as elements with intermediate properties or metals and nonmetals, with metals on the left side of the periodic table and metals on the right. Two special classes of elements with special properties discussed are noble gasses, which combine with almost no other elements, and rare-earth elements that are so similar to one another that they are extremely difficult to separate.
Alkali Metals are the elements in Group IA of the periodic table. The members of the family are lithium, sodium, potassium, rubidium, cesium, and francium. All six elements have the properties of metals except they are softer and less dense. They can be cut with a knife. They are the most reactive metals. They are so reactive that they are never found in nature. They are always combined with other elements. The alkali metals have only one electron in their outermost shell, so alkali metals form positive ions.
Alkaline Earth Metals are beryllium, magnesium, calcium, strontium, barium, and radium. These elements, which are harder and more dense than the alkali metals, also have higher melting points and boiling points. They are highly reactive, but not as active as the alkali metals. Like the alkali metals, the alkaline metals are never found free in nature. The alkaline earth metals have two electrons in their outermost energy level, so they also form positive ions.
Transition Metals have properties similiar to one another and to other metals, but their properties do not fit in with those of any other family. Most transition metals are excellent conductors of heat and electricity. Most have high melting points and are hard. Transition metals are much less active than the alkali and alkaline earth metals. Many transition metals combine chemically with oxygen to form compounds called oxides. Many transition metals have more than one oxidation number. Transition metals form compounds that are brightly colored.
From Metals to Non-Metals in groups IIIA to VIA of the periodic table elements have properties which change from metallic to nonmetallic. These groups include the boron family, carbon family, nitrogen family, and oxygen family.
Boron, the first element in the boron family is a metalloid. Aluminum, which is right beneath boron, is by its position a metalloid. But the properties of aluminum are usually those of metals. The other members of the boron family ...gallium, indium, and thallium, are metals. Boron, which is hard and brittle, is never found in nature in the free state. It is usually found combined with oxygen. The compound boric oxide is important in making heat-resistant glass. Boric acid is commonly used as eyewash and antiseptic. The compound borax is useful as a cleaning agent and water softener.
Aluminum is the most abundant metal and the third most abundant element in the earth's crust. Aluminum is found as aluminum oxide in the ore called bauxite. Aluminum is extremely valuable in industry. It is light, strong, and does not tarnish in air. It is a good conductor and is used in wiring, airplane parts, household items.
The Carbon family includes the elements carbon, silicon, germanium, tin, and lead. Carbon can combine with other elements in a great variety of ways. Millions of carbon compounds called "organic compounds." Carbon is called the basis for life because all living things contain organic compounds.
Silicon is the second most abundant element in the earth's crust. Silicon is used in glass and incement. It is also used in solar cells. Solar cells convert the energy of sunlight into electric energy.
Germanium is a metalloid used in transistors. Transistors are devices found in many electronic instruments, such as radios and televisions. Tin is a metal which resists rusting and corrosion. The most dense element in the carbon family is the metal lead.Lead forms poisonous compounds.
The Nitrogen family consists of nitrogen, phosphorus, arsenic, antimony, and bismuth. Nitrogen and phosphorus are nonmetals. Arsenic is a metalloid with mostly nonmetallic properties. Antimony is a metalloid with mostly metallic properties. Bismuth is the most metallic element in the family. All members of the nitrogen family have five electrons in their outermost energy level. These elements lose electrons easily.
The Oxygen family includes oxygen, sulfur, selenium, tellurium, and polonium. All of these have six electrons in their outermost energy level. Their properties go from nonmetallic in oxygen and sulfur to metalloid in selenium and tellurium to metallic in polonium.
Halogens are the elements in family VIIA. They are strongly nonmetallic. The halogens include fluorine, chlorine, bromine, iodine, and astatine. They are the most active nonmetals. The chemical reactivity of the halogens is due to the number of electrons in the outermost energy levels of their atoms. Fluorine is the most active halogen. They have low melting points and boiling points. In the gas phase they exist as diatomic elements. Halongens combine readily with metals to form a class of compounds known as salts.
Noble Gasses are colorless gasses that are extremely unreactive. Because do not readily combine with other elements to form compounds, the noble gasses are called inert. The family of noble gasses includes helium, neon, argon, krypton, xenon, and radon. All the noble gasses are found in small amounts in the earth's atomsphere. One important property of the noble gasses is their inactivity. They are inactive because their outermost energy level is full.

posted by James @ 7:03 AM