Unit 4: Periodic Table

alkali metals

are elements in group 1. these metals have single valence electron and are extremely reactive. the reactivity of alkali metals increases from the top of the group to the bottom.

carbon group

are elements in group 14. each element has four valence electrons. life on earth would not exist without carbon. except for water most of the compounds in your body contain carbon. reactions that occur in the cells of your body are controlled by carbon compounds. silicon is the second most abundant element in the earth's crust.

halogen

are elements in group 17. each halogen has seven valence electrons. despite their physical differences, the halogens have similar chemical properties. they are highly reactive nonmetals. halogens react easily with most metals. The reactivity of halogens decreases from the top of the group to the bottom

noble gases

are elements in group 18. helium has two valence electrons. each of the other noble gases has eight valence electrons. the noble gases are colorless and odorless and extremely unreactive. an element that does not react easily with other elements can be useful such as making computer chips. all noble gases except radon are used in "neon" lights.

alkaline earth metals

are elements in group 2. all alkaline earth metals have two valence electrons. metals in group 2 are harder than metals in group 1. differences in reactivity among the alkaline earth metals are shown by the way they react with water, they are moderately reactive. magnesium and calcium have essential biological functions and are common alkaline earth metals.

classification of elements

can be done in 3 ways: state of matter, naturally occurs or not, and general properties

variation across a period

changes from left to right across the table except for period 1. across the period from left to right, the elements become less metallic and more nonmetallic in their properties.

metals

elements that are good conductors of electric current and heat. except for mercury, they are solids at room temperature. most are malleable. many are ductile meaning they can be drawn into thin wires. a majority of the elements are classified as this. some are extremely reactive and some do not react easily.

nonmetals

elements that are poor conductors of heat and electric current. many are gases at room temperature. these that are solid at room temp tend to be brittle. these vary in chemical properties, some are very reactive and some are unreactive. these generally have properties opposite of those of metals

transition metals

elements that form a bridge between the elements on the left and right sides of the table. they are groups 3-12. many of these form compounds with distinctive colors. they are used in the production of colored glass. these are so similar in properties it can be difficult to distinguish them.

metalliods

elements with properties that fall between those of metals and nonmetals. a *blank's* ability to conduct electric current varies at room temp

inert

is having little or no ability to react, as nitrogen that occurs uncombined in the atmosphere. noble gases are unreactive and are called inert

extremely reactive

is the tendency to react with other atoms, molecules, or compounds to undergo a chemical reaction; to react easily, group 1, alkali metals: francium is the most reactive element. group 17, halogens: fluorine is the most reactive element