Honors Chemistry Chapter 6. The Periodic Table

Transcription

1 Honors Chemistry Chapter 6 The Periodic Table

2 6.1 Early Classification: Dobereiner & Newlands 1817 Johann Dobereiner found Ca, Ba, & Sr had similar props Atomic mass of Sr was ~ midway betw Ca & 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 Classification: Dobereiner & Newlands 1863 John Newlands arranged elems in order of atomic mass Noted a repetition of similar props every 8 th elem 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 1 st 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 1 st 2 elems fill 1 st energy level & 1 st row of table 3 rd elem ends in 2s 1 similar to H goes under it. Be 2s 2 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 2 nd energy level goes under He

10 Construction of Table: Na thru Ar fill 3 rd energy level, make up 3 rd row K & Ca begin 4 th energy level start 4 th 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 3 rd 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, elems w/ 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 f 1 f 14 w/ 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 include both metals & nonmetals Top of ea group is nonmetallic Metallic character of elem incr 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.