Section 1.3 The Periodic Table

Periodic Table Introduction The arrangement of the elements show how chemical properties can be related The arrangement shows the relationship between electronic structure and chemical properties The elements are arranged in order of increasing atomic number reading from left to right and from the top to the bottom

Groups A group (AKA family) is a vertical column Each group has the same number of valence electrons This gives the group similar chemical properties The groups are numbered from 1 to 18

More About Groups The group number is the same as the number of valence electrons for the neutral atom in that group for the left side, and the group number minus 10 for the right side. Example: carbon is in group 14 and has 4 valence electrons Usually the noble gases are thought of as having 8 valence electrons, i.e. their outermost energy level is full

Periods A period is a row in the periodic table Periods are numbered 1-7 Each period corresponds to a new main energy level The first element in each period has only one electron in its outer shell The second-to-last element in the period only requires one more electron to fill the outer shell

More About Periods The last element in a period has all its electron shells filled and are known as the noble gases The noble gases experience very little chemical reactivity

Periodicity Periodicity is the regular repeating of properties according to the arrangement of elements in the periodic table Chemical and physical properties of elements show periodicity if the elements are arranged in order of increasing atomic numbers

Metals Metal: an element that is a good conductor of heat and electricity Most metals are solids at room temperature Most have the property of malleability (can be hammered or rolled into thin sheets) Most are ductile (can be drawn into a wire) Metals have high tensile strength (the ability to resist breaking when pulled)

More About Metals Most metals have luster (tend to be shiny) Metals can also have diverse properties Mercury is a liquid at room temperature Group one metals are very soft while others are hard Some are brittle while others are very malleable

Metals

Nonmetals A nonmetal is an element that is a poor conductor of heat and electricity Many are gases at room temperature One nonmetal, bromine, is a liquid Solid nonmetals include C, P, Se, S, and I. They tend to be brittle.

Nonmetals

Metalloids A metalloid is an element that has some characteristics of metals and some characteristics of nonmetals All are solids at room temperature Less malleable than metals, but not as brittle at nonmetals Tend to be semiconductors Used in computers, digital watches, TV, and radios

Metalloids

Noble Gases Noble gases are the elements in group 18 Very unreactive All are gases at room temperature Ne, Ar, Kr, and Xe are used in lighting He is used in party balloons and weather balloons

Two Other Sets of Elements Two sets of elements are placed below the periodic table They are called the lanthanides and the actinides They are metallic, and fit into the table just after elements 57 and 89. They are placed below the table to keep the table from being too wide.