Honors Chemistry Chapter 6The Periodic Table

6.1 Early Attempts @ Classification:Dobereiner & Newlands1817 – 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 propsIn ea triad, the middle elem had

an atomic mass ~ ½ way betw the other 2 elems

6.1 Early Attempts @ Classification:Dobereiner & Newlands1863 – 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 TableDmitri 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 TableMendeleev & 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 TableWhen all elems were placed in

order of incr atomic masses, Te & I were in the wrong columns◦If switched, they were in correct

columnsAs more elems were discovered,

other pairs were also switched

6.3 Problems w/ Mendeleev’s TableHenry 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 TableAtomic # gives # of p+’s & # of

e-’sCertain 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 rowK & Ca begin 4th energy level –

start 4th row

6.5 Transition ElementsSc begins to fill sublevel – starts

new columnSc 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 ElementsNext 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

ElementsLanthanoid 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 & ActinoidsBoth series are placed below the

tablePeriod – all elems in a horizontal

rowGroup – all elems in the same

vertical column

6.7 Octet RuleWhen 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 RuleOctet 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 ConfigurationsIn the periodic table, elems w/

similar props are in a columnAn 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 ConfigurationsElems 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 ConfigurationsElems 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 & NonmetalsGroups 1 & 2 contain the most

active metalsGroup 1 (except H) – Alkali Metal

FamilyGroup 2 – Alkaline Earth Metal

Family

6.9 Metals & NonmetalsNonmetals 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 & NonmetalsElems 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 & NonmetalsGeneral Rule:

◦3 or less e-’s in outer level – metals◦5 or more e-’s in outer level –

nonmetalsMetalloids – elems which have

props of both metals & nonmetalsStairstep line in table is a rough

dividing line betw metals & nonmental◦Elems that lie along this line are

usually metalloids

6.9 Metals & NonmetalsGroups 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 & NonmetalsMetals 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.