1. Chapter 4

2. Learning Objectives Understand the development and need for the periodic table Identify the properties and locations of families on the periodic table Identify trends of atomic properties

3. Dmitri Mendeleev 1869 63 known Elements Arranged by atomic mass

4. Henry Moseley 1913 Organized elements by atomic number rather than atomic mass

5. Modern Versions – all follow the periodic law Theorodore Benfrey - 1960 Timothy Stowe

6. ADOMAH – good for electron config.

8. Why do the properties of elements repeat themselves at regular intervals? Valence Electrons

9. Periods Groups

10. Main-Group Elements Wide range of properties – Solids, liquids, gases – About half are metals – Many are very reactive, some are not reactive – Silicon and oxygen account for four of every five atoms found on or near Earth’s surface

11. Group 1 – Alkali Metals React with water to form alkaline solutions One valence electron – very reactive Not found in nature as pure elements Metals are very soft, easily cut with a knife Good conductors of electricity

12. Group 2 – Alkaline-Earth Metals Slightly less reactive than alkali metals – (still very reactive) Two valence electrons Harder than alkali metals, higher melting points Last one in the family, Radium is radioactive

13. Metals Excellent conductors of electricity Conductors of heat Some are ductile (can be drawn into a wire) Some are malleable (can be hammered or rolled into sheets) Mg Sr Hg

14. Transition Metals Group members do not have identical electron configurations May lose different numbers of valence electrons during reactions Less reactive than Group 1&2 Gold, platinum, and palladium are the least reactive TMs Good conductors of heat Ductile and malleable

15. NonMetals C, N, O, P, S, Se Not good conductors of heat or electricity Brittle No metallic luster Most abundant elements on earth

16. Metalloids B, Si, Ge, As, Sb, Te, Po Behave like nonmetals chemically and physically Electrical conductivity like metals Semiconductors – conduct electricity weakly

17. Group 7 - Halogens Most reactive group of non-metals Seven valence electrons (one short of stable) F 2, Cl 2 are gases at RT Br 2 is a liquid at RT I 2 and At 2 are solids at RT

18. Group 8 – Noble Gases Also known as noble gases Mostly unreactive – Full set of electrons in outer shell

19. Lanthanides and Actinides Fill “f” orbitals Called Lanthanides because they follow Lanthanum on the periodic table Actinides follow – Actinium All actinides are radioactive (unstable nuclei) Shiny metals Similar in reactivity to alkaline-earth metals

20. Atomic Radius How do you measure the radius of an atom?

21. Atomic Radius One way - Bond Radius

22. Atomic Radius Trends

23. Ionization Energy The energy required to remove an electron from an atom of an ion

24. Ionization Energy Trends

25. Electron Affinity The energy change that occurs when a neutral atom gains an electron

26. Electronegativity A measure of the ability of an atom in a compound to attract electrons

27. Electronegativity Why is the no color-coding for He, Ne, and Ar?