Honors Chemistry Chapter 6

1. Honors Chemistry Chapter 6 The Periodic Table

2. 6.1 Early Attempts @ Classification:Dobereiner & Newlands • 1817 – Johann Dobereiner found Ca, Ba, & Sr had similar props • Atomic mass of Sr was ~ midway betwCa & Ba • Grouped them into Triads • Found several triads w/ similar props • In ea triad, the middle elem had an atomic mass ~ ½ way betw the other 2 elems

3. 6.1 Early Attempts @ Classification:Dobereiner & Newlands • 1863 – John Newlands arranged elems in order of atomic mass • Noted a repetition of similar props every 8thelem • Called this the Law of Octaves

4. 6.2 Mendeleev’s Periodic Table • Dmitri Mendeleev – also put elems in a table • Said props of elems were a function of their atomic masses • Felt props occurred after periods varying in length • 7 elems in 1st 2 periods, 17 elems in next 2

5. 6.2 Mendeleev’s Periodic Table • Mendeleev & Lothar Meyer, working separately, made an 8 column table of elems • Mendeleev left blanks in table to group all elems w/ similar props in the same column • Thought elems had yet to be discovered • Predicted props & atomic masses of several elems • Eventually discovered & his predictions were very close • Said “props of elems are a periodic function of their atomic masses” – Periodic Law

6. 6.3 Problems w/ Mendeleev’s Table • When all elems were placed in order of incr atomic masses, Te & I were in the wrong columns • If switched, they were in correct columns • As more elems were discovered, other pairs were also switched

7. 6.3 Problems w/ Mendeleev’s Table • Henry Moseley found atomic number of many elems • Result – periodic law was revised: • The properties of the elements are a periodic function of their atomic number.

8. 6.4 Modern Periodic Table • Atomic # gives # of p+’s & # of e-’s • Certain e- arrangements are repeated periodically • Elems w/ similar e- configs are placed in the same column • Can also list elems in the column in order of incr principal quantum # • This forms the Periodic Table.

9. Construction of Table: • Align elems w/ similar outer e- configs • 1st 2 elems fill 1st energy level & 1st row of table • 3rdelem ends in 2s1 – similar to H – goes under it. • Be – 2s2 – similar to He, but doesn’t fill energy level – does not go under it • B thru Ne; have e-’s in p sublevel – new columns • Ne fills 2nd energy level – goes under He

10. Construction of Table: • Na thru Ar fill 3rd energy level, make up 3rd row • K & Ca begin 4th energy level – start 4th row

11. 6.5 Transition Elements • Sc begins to fill sublevel – starts new column • Sc thru Zn fill sublevel & head new columns • * Cr & Cu have 1 e- in highest energy level due to stability of ½ filled & completely filled sublevels • Elements in columns 3-12 (IIIB – IIB)

12. 6.5 Transition Elements • Next 6 elems have e-’s in highest p sublevel • Elems in column 18 have 8 e-’s in outer level (except He) • Next e- begins a new row

13. The Lanthanoids & Actinoids • - Sometimes called Rare Earth Elements • Lanthanoid Series – La thru Yb begin filling the 4f sublevel • *Assume elems have predicted configs except for ½ filled & complete filled sublevels • Actinoid Series – Ac thru No – fill 5f sublevel

14. The Lanthanoids & Actinoids • Both series are placed below the table • Period – all elems in a horizontal row • Group – all elems in the same vertical column

15. 6.7 Octet Rule • When s & p e-’s are in the highest energy level of an atom, they are in the outer level • d & f e-’s can never be in outer level of neutral atom • \ the largest # of e-’s in outer level is 8 • These 8 e-’s are called an Octet. • An atom w/ 8 e-’s in outer level is considered to have a full outer level

16. 6.7 Octet Rule • Octet Rule – an atom w/ 8 e-’s in their outer level is chemically stable • He is also considered stable bec. Its out level is full • Can only hold 2 e-’s • It is sometimes possible to force the outer level of an elem in 3rd or higher period to hold more than 8 e-’s • - Extended Octet • Noble gas comps are formed this way

17. Surveying the Table: Electron Configurations • In the periodic table, elemsw/ similar props are in a column • An atom’s chemical props are determined by its e- config • \ the periodic table is constructed on the basis of e- config

18. Surveying the Table: Electron Configurations • Elems in columns labeled “A” have their highest energy e- in an outer s or p sublevel • The coef is the same as the # of the period

19. Surveying the Table: Electron Configurations • Elems in columns labeled “B” have their highest energy e- in a d sublevel, one level below the outer level • The coef is 1 less than the period # • Lanthanoids & Actinoids end in f1 – f14w/ coef 2 less than the period # • Full or ½ full sublevels are more stable than other arrangements

20. 6.9 Metals & Nonmetals • Groups 1 & 2 contain the most active metals • Group 1 (except H) – Alkali Metal Family • Group 2 – Alkaline Earth Metal Family

21. 6.9 Metals & Nonmetals • Nonmetals are on the right side of the table • Group 16 – Chalcogen Family • Group 17 – Halogen Family • Group 18 – Noble Gases • Metals – hard, shiny & conduct heat & electricity well • Nonmetals – generally gases or brittle solids, dull, insulators

22. 6.9 Metals & Nonmetals • Elems are classified as metals or nonmetals on the basis of e- structure. • Metals have few e-’s in outer level • Tend to lose outer e-’s & form (+) ions when forming compounds • Nonmetals have more e-’s in outer level • Gain e-’s to form (-) ions when forming comps • May also share outer e-’s w/ other atoms

23. 6.9 Metals & Nonmetals • General Rule: • 3 or less e-’s in outer level – metals • 5 or more e-’s in outer level – nonmetals • Metalloids – elems which have props of both metals & nonmetals • Stairstep line in table is a rough dividing line betw metals & nonmental • Elems that lie along this line are usually metalloids

24. 6.9 Metals & Nonmetals • Groups 13-15 include both metals & nonmetals • Top of ea group is nonmetallic • Metallic character of elemincr toward the bottom of the table.

25. 6.9 Metals & Nonmetals • Metals are on the left side of table. • Nonmetals are on the right side of table. • Most elems are metallic. • The most unreactive atoms are the noble gases • Chemically stable bec of octet rule.