Discovering the Periodic Table

1. Trends in the Periodic Table

2. The Periodic Table Dmitri Mendeleev (1834-1907) determined the properties of every known element at the time Atomic Mass Density Colour Melting Point Boiling Point

3. The Periodic Table: Periods Mendeleev arranged the known elements in order of increasing atomic mass He found that the properties of the elements repeated at definite, or PERIODIC , intervals Na has similar properties to Li and K

4. The Modern Periodic Table: Atomic Number In 1915, the Periodic Table was reorganized based on the elements atomic structure Each element has an ATOMIC NUMBER , which is unique to each element The atomic number begins with H (1) in the upper-left hand corner, and moves from Left to Right

5. The Modern Periodic Table: Groups Vertical columns in the periodic table Chemical families Elements in a group share very similar properties Numbered from 1-18 Elements in the same GROUP have the same number of atomic SHELLS where VALENCE ELECTRONS (outer electrons) are held 1 2 3 4 3 2 1 0

6. Nonmetals Metals Metalloids Elements are grouped based on specific properties:

7. Metals Metals Non-Metals Non-Metals Metalloids Metalloids

8. The Modern Periodic Table: Characteristics of Groups The number of valence electrons in the elements is same in a group. The atomic radii increase from top to bottom Metallic Elements: Metallic character and chemical reactivity increase from top to bottom Non-Metallic Elements: Metallic character and chemical reactivity decrease from top to bottom

9. Elements are ordered in the periodic table according to reactivity and atomic number: Na and K react with Water Na K Mg and Ca React with Hydrochloric Acid (Same Group) Mg Ca F, Cl, I are gases F Cl I

10. The Modern Periodic Table: Groups of Elements 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 2

11. Group 1: Alkali Metals Very reactive metals that do not occur freely in nature (Cs, Fr the most reactive) Valence Electrons: One; ready to lose that one electron to bond with other elements. Properties: Malleable, ductile, good conductors of heat and electricity, softer than most metals Can explode if exposed to water.

12. Group 2: Alkaline Earth Metals Very reactive Valence Electrons: 2; can bond easily with other elements Not found free in nature

13. Groups 3-12: Transition Metals Properties: Ductile, malleable, conduct electricity and heat Valence Electrons: present in more than one shell Iron, cobalt, and nickel are the only elements known to produce a magnetic field.

14. Groups 13-15: Other Metals Properties: Ductile and malleable, solid, high density, opaque Valence Electrons : present in their outer shell.

15. Metalloids Along the stair-step line that distinguishes metals from non-metals Al is an exception as it is classified as an Other Metal Properties: Similar to metals and non-metals Si and Ge are semi-conductors (can carry an electrical charge under special conditions; used in calculators and computers)

16. Group 14-16: Non-Metals Properties: Do not conduct electricity or heat very well, brittle, not malleable or ductile, no luster, do not reflect light Exist as gases (N, O) or solids (C, S)

17. Group 17: Halogens Salt-former, compounds containing halogens are called salts Valence Electrons: 7; will bond easily with Alkali Metals. Exist as solids (I, At), liquid (Br), and gas (F, Cl)

18. Group 18: Noble Gases Valence Electrons: 0; prevents gases from readily forming compounds Very stable because they have the maximum electrons in their outer shell

19. Rare Earth Elements Lanthanide and Actinide series (Group 3 and Period 6-7) One element of the lanthanide series and most of the elements in the actinide series are trans- uranium (synthetic or man-made)

20. Mendeleevs Periodic Law If the elements are arranged according to their atomic mass, a pattern can be seen in which similar properties occur regularly