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Honors Chemistry
Chapter 6
The Periodic Table
6.1 Early Attempts @ 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
6.1 Early Attempts @ Classification:
Dobereiner & Newlands

1863 – John Newlands arranged elems in
order of atomic mass
◦ Noted a repetition of similar props every 8th
elem
 Called this the Law of Octaves
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
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
6.3 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
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.
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.
Construction of Table:

Align elems w/ similar outer e- configs
◦ 1st 2 elems fill 1st energy level & 1st row of
table
◦ 3rd elem 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
Construction of Table:
Na thru Ar fill 3rd energy level, make up
3rd row
 K & Ca begin 4th energy level – start 4th
row

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)

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
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
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

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
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
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
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
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 – f14 w/
coef 2 less than the period #
 Full or ½ full sublevels are more stable
than other arrangements

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

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

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
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
6.9 Metals & Nonmetals

Groups 13-15 include both metals &
nonmetals
◦ Top of ea group is nonmetallic
◦ Metallic character of elem incr toward the
bottom of the table.
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.