The Periodic Table

Chapter 15Section 1 Introducing the Periodic Table

A. By 1830 fifty-five different elements had been isolated and named.

1. In 1869 Mendeleev arranged elements in order of increasing atomic mass and found that elements with similar properties fell into groups.

2. Moseley improved the periodic table by arranging the elements according to atomic number instead of atomic mass

B. The modern periodic table contains seven periods or rows of elements whose properties change gradually and eighteen groups of columns, each with a family of elements having similar properties1. Groups 1 and 2 along with groups 13 thru 18 are called the representative elements.2. Groups 3 and 12 are called the transition elements.

3. A metal has luster, conducts heat and electricity, is malleable and ductile.

4. Nonmetals are usually gases or brittle solids at room temperature

5. A metalloid shares properties with metals and nonmetals

6. Symbols are abbreviation often base on the elements name.

Section 2 Representative ElementsA. Groups 1 and 2 are active metals found in

nature combined with other elements; although hydrogen is placed in Group 1, it is not a metal and it shares properties with Groups 1 and 17

1. Alkali metals- silvery solids with low densities and low melting points; they increase in reactivity from top to bottom of the periodic table

2. Alkaline earth metals- are denser, harder, have higher melting points, and are slightly less reactive than alkali metals in the same period.

B. Groups 13 through 18 may contain metals, nonmetal, or metalloids in solid, liquid, or gas form.1. The Boron family elements in group 13 are all metals except boron, which is a metalloid; these elements are used in a variety products.

2. The carbon group elements are all metalloids or metals, except for carbon itself.

a. carbon is found in all living things and exists in several forms.

b. Silicon and germanium are used in electronics as semiconductor

c. Tin and lead are the two heaviest elements in Group 14

3. The nitrogen group contains nitrogen and phosphorous, which are required by living things and which are used in industry

4. The oxygen family contains oxygen and sulfur, which are essential for life and used to manufacture many products.

5. The halogen groups elements form salts with sodium and with other alkali metals

6. The noble gases rarely combine with other elements; they are often used in lighting and inflating balloons

Section 3 Transition elements

A. Groups 3 to 12 are the transition elements; most are combined with other elements in ores.

1. The iron triad is composed of iron, cobalt, and nickel; these metals have magnetic properties.

2. Several transition elements can be used as catalysts, which are substances that make reactions occur faster without changing itself

B. The inner transition elements are called lanthanides and actinides.1. The lanthanides are soft metals and were once thought to be rare.2. All the actinides are radioactive; several are synthetic elements that do not occur naturally.3. Dental materials are sometimes made of new composites, resins, and porcelains.