1. The Periodic Table Chapter 6 Notes

2. History of the PT Dobereiner –German Chemist –Proposed “triads” in 1829: grouping of 3 elements with similar properties –Observed that melting point decreased and density increased as the atomic mass of an element increased

3. Mendeleev –Russian Chemist –Published a table of elements in 1869 in which the elements were organized by increasing atomic mass –First periodic table to use rows and columns –Left “missing spots” for elements not yet discovered –Tellurium (mass = 128) and Iodine (mass = 127) were in the wrong order – thought the masses were wrong

4. Mendeleev’s Periodic Table

5. The Modern PT Very similar to the periodic table developed by Mendeleev Organized by horizontal rows (called periods) and vertical columns (called groups or families) Shows a pattern of physical and chemical properties Uses atomic number to order elements, NOT atomic mass

6. The Modern Periodic Table

7. Within a Period (Row) Add one proton and one electron each time you move one element across a row 1A – s 1 2A – s 2 3A – s 2 p 1 4A – s 2 p 2 5A – s 2 p 3 6A – s 2 p 4 7A – s 2 p 5 8A – s 2 p 6

8. Within a Group (Column): 1 234567 8 The number of valence electrons (outermost electrons) = the group number

9. Because the number of valence electrons within a group are the same, elements within a group have similar physical and chemical properties For example, what happens when an alkali metal comes into contact with water?what happens when an alkali metal comes into contact with water? Alkali metals react violently with water to form hydrogen gas and release a lot of energy!

10. Classification of Elements Metals –Have luster (shine) –Conduct heat and electricity –Malleable (can bend without breaking) –Solids (except for mercury) –High melting points –Groups 1A, 2A and all of Group B Group B – Transition Metals Bottom 2 Rows – Inner Transition Metals –Lanthanides – top row –Actinides – bottom row (also called the Rare Earth Metals)

11. Classification of Elements Nonmetals –Do not conduct heat or electricity –Are brittle –Many are gases at room temperature –Do not have luster –Lower melting points –Located in Groups 3A – 8A

12. Classification of Elements Metalloids –Have some properties of metals and other properties of nonmetals depending on the conditions the element is under (temperature, pressure, etc.) –Border the metals and nonmetals on the periodic table –Semiconductors: conduct electricity better than a nonmetal but not as well as a metal

13. Group Characteristics Representative Elements –A–All Group A elements –R–Represent the entire spectrum of element characteristics Metals Nonmetals Metalloids Solids Liquids Gases

14. Transition Elements –All Group B elements –Show a gradual transition in properties from metals to nonmetals –Used on alloys (metal mixtures) –Have high melting and boiling points

15. Inner Transition Metals –“f block” –Lanthanides – top row Also called the “Rare Earth Metals” Found naturally in the Earth’s crust used in the glass and TV picture tube industry –Actinides – bottom row All are radioactive U and Pu are used as nuclear fuels Some are used for cancer therapy

16. Alkali Metals Group 1A All have one valence electron All end in the electron configuration s 1 Soft, silvery white metals Good conductors of heat and electricity Very reactive

17. Alkaline Earth Metals Group 2A All have 2 valence electrons All end in the electron configuration s 2 Less reactive than the alkali metals More dense, harder, and have a higher melting point

18. Boron Group Group 3A All have 3 valence electrons All end in the electron configuration s 2 p 1 Not very reactive Silvery, fairly soft, and good conductors of heat and electricity

19. Carbon Group Group 4A All have 4 valence electrons All end in the electron configuration s 2 p 2 Form bonds by sharing electrons Mixture of metals, nonmetals, and metalloids

20. Nitrogen Group Group 5A All have 5 valence electrons All end in the electron configuration s 2 p 3 Nonmetals and metalloids

21. Chalcogens Group 6A All have 6 valence electrons All end in the electron configuration s 2 p 4 Nonmetals and metalloids Very reactive

22. Halogens Group 7A All have 7 valence electrons All end in the electron configuration s 2 p 5 All are nonmetals Exist as diatomic molecules – two atoms of the same element bonded together (Cl 2, F 2 ) Very reactive

23. Noble Gases Group 8A All have 8 valence electrons (except for Helium which has 2 valence electrons All end in the electron configuration s 2 p 6 All are gases All have a full outer shell which causes them to be unreactive (previously called inert)

24. Periodic Trends Atomic Radius –The radius of an atom –As you move across a period, the atomic radius decreases because the greater number of protons in the nucleus increases the magnetic pull on the electrons making the atom smaller 3p + 4n 0 3e - 4p+ 5n 0 4e-Lithium atom Beryllium atom

25. –As you move down a group, the atomic radius increases because there are more energy levels so electrons are farther away from the nucleus Lithium atomSodium atom 2 energy levels 3 energy levels

26. Ionic Radius –The radius of an ion (an ion is an atom that has gained or lost electrons causing it to have an overall positive or negative charge) –As you move across a period, the ionic radius decreases because the greater number of protons in the nucleus increases the magnetic pull on the electrons making the atom smaller –The trend is NOT smooth across a period because metals lose electrons and nonmetals gain electrons – there is a spike around the metalloids on the periodic table

28. –As you move down a group, the ionic radius increases because there are more energy levels so electrons are farther away from the nucleus

29. Ionization Energy –The energy required to REMOVE an electron from an atom –As you move across a period, ionization energy increases because metals easily lose electrons and nonmetals strongly hold onto their electrons, so it would require less energy to remove an electron from a metal and more energy to remove an electron from a nonmetal –As you move down a group, ionization energy decreases because the further the electron is from the nucleus, the less attraction there is between the protons in the nucleus and the electrons, so it is easier to remove the electron from the shell

31. Electronegativity –How well an atom attracts an electron for bonding –As you move across a period, electronegativity increases because metals then to lose electrons and nonmetals tend to gain electrons –As you move down a group, electronegativity decreases because the energy levels are farther away from the nucleus and the magnetic pull between the positive nucleus and the electrons decreases