Elements and the Periodic Table

1. Elements and the Periodic Table

2. A classification scheme for matter.

3. Names of Elements • The first 103 elements have internationally accepted names, which are derived from: • The compound or substance in which the element was discovered • An unusual or identifying property of the element • Places, cities, and countries • Famous scientists • Greek mythology • Astronomical objects.

4. The elements of aluminum, Iron, Oxygen, and Silicon make up about 88 percent of the earth's solid surface. Water on the surface and in the air as clouds and fog is made up of hydrogen and oxygen. The air is 99 percent nitrogen and oxygen. Hydrogen, oxygen, and carbon make up 97 percent of a person. Thus almost everything you see in this picture us made up of just six elements.

5. Chemical Symbols • There are about a dozen common elements that have s single capitalized letter for their symbol • The rest, that have permanent names have two letters. • the first is capitalized and the second is lower case. • Some elements have symbols from their Latin names. • Ten of the elements have symbols from their Latin or German names.

6. Charge (if ion) Atomic Mass Symbol Atomic Number

7. Rhenium Protons: 75 Neutrons: 111 Electrons: 75 Re 186 75

8. Rhenium isotope Protons: 75 Neutrons: 112 Electrons: 75 Re 187 75

9. Dmitri Medeleev gave us a functional scheme with which to classify elements. • Mendeleev’s scheme was based on chemical properties of the elements. • It was noticed that the chemical properties of elements increased in a periodic manner. • The periodicity of the elements was demonstrated by Medeleev when he used the table to predict to occurrence and chemical properties of elements which had not yet been discovered.

10. The Modern Periodic Table

11. Introduction • The periodic table is made up of rows of elements and columns. • An element is identified by its chemical symbol. • The number above the symbol is the atomic number • The number below the symbol is the rounded atomic weight of the element. • A row is called a period • A column is called a group

12. (A) Periods of the periodic table, and (B) groups of the periodic table.

13. Each period ends with a completely filled outer shell that has the maximum number of electrons for that shell. • The number identifying the A families identifies the number of electrons in the outer shell, except helium • The outer shell electrons are responsible for chemical reactions. • Group A elements are called representative elements • Group B elements are called transition elements.

14. Chemical “Families” • IA are called alkali metals because the react with water to from an alkaline solution • Group IIA are called the alkali earth metals because they are reactive, but not as reactive as Group IA. • They are also soft metals like Earth. • Group VIIA are the halogens • These need only one electron to fill their outer shell • They are very reactive. • Group VIIIA are the noble gases as they have completely filled outer shells • They are almost non reactive.

15. Four chemical families of the periodic table: the alkali metals (IA), the alkaline earth metals (IIA), halogens (VII), and the noble gases (VIIIA).

16. Metal: Elements that are usually solids at room temperature. Most elements are metals. Non-Metal: Elements in the upper right corner of the periodic Table. Their chemical and physical properties are different from metals. Metalloid: Elements that lie on a diagonal line between the Metals and non-metals. Their chemical and physical properties are intermediate between the two.

17. When an atom or molecule gain or loses an electron it becomes an ion. • A cation has lost an electron and therefore has a positive charge • An anion has gained an electron and therefore has a negative charge.

18. Elements with 1, 2, or 3 electrons in their outer shell tend to lose electrons to fill their outer shell and become cations. • These are the metals which always tend to lose electrons. • Elements with 5 to 7 electrons in their outer shell tend to gain electrons to fill their outer shell and become anions. • These are the nonmetals which always tend to gain electrons. • Semiconductors (metalloids) occur at the dividing line between metals and nonmetals.

19. EXAMPLE What would the charge be on a sodium ion? Since sodium in in Group IA it is a metal and so would LOSE an electron You can tell how many would be lost by the group number Group 1A elements lose 1 electron So the charge would be +1 Remember an electron is negatively charged. When you lose them atom becomes positively charged… when you gain them it becomes negatively charged

20. EXAMPLE How would you right the symbol for the sodium CATION? Na +1 How many outer electrons does sodium have before it loses one? It has 1…remember the group number!