History Of The Periodic Table (Chemistry Unit 3)

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I n t
h e
1800s,
there w ere
two ways t
o o r
g ani
se the ele me nt
:
T he i
r Relat
ive at
o mic
Mass and their
physic al an d
chemi cal propert
ie s.
Th e
atomi c
str
u ct
ure wa s
un known ba ck
then ( or an y t
hing ab out
pr
oton s
or
el
ectrons)
so
there
w a s n o such t
hin gs
as an
a t omi c n umb er.
th
I n t
h e
20 cent
ury,
pr oto ns
and electro ns
w er
e di
s co v er
e d
lea di
ng t
o t
he at
omic
numb er
s (but
w e don 't
n ee d
thi
s yet).
B efor
e
then, t
hey we r e
a bl
e t
o
me as ur e the
relative atomic mass so
th ey
w er
e
ar
range d
b ased on t
h i
s.
Wh en
this was done a periodic pattern w as
id en t
if
ied i
n t
h e
p hys i
cal
an d
chemical
p r
op er
ti
e s.
Newlands' Law Of Octaves
I n 1864 (r
e me mbe r
t
h i
s y ear!)
,
Joh n N ew l
ands sa w th at
every eighth element
had a
very si
mi l
ar
p r
o pe rt
ies.
So
he l
i
s ted t
hem in
row s
of sev en.
Th e
sets of
eight
w as
c a l
led t
he Ne w la nd'
O ct
a ve s.
r d
H ow ever,
the
p at
tern di
d n'
t
w ork
up aft er
the
3 r
o w (transi
ti
o n me tal
s)
I t
all
broke because
h e
d i
d not
leave
a n y gaps f or an y mo re
e leme nts.
S o,
hi
s work wa s
ignored (
p o or
Joh n )
N ew l
ands
p r
ese nt
ed his i
dea s
to
the
C hemical So ci
e ty i
n
186 5
(
reme mb er!
) But
he
w ork was not
ac ce pt
e d
bec au se :
T h e
group s
h ad
e l
eme n t
s t
hat di
dn't h ave
the
same properti
es suc h a s carbon
a nd t i
tani
um.
H e
mixe d up t
he non me tal
s wit
h
me ta ls
such
as oxygen
a nd
iron.
H e
also didn'
t l
eave an y
gap s
for
an y o t
her
eleme nt
s
that
h adn'
t be en
found yet.

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Dmitri Mendeleev
In 1 869,
D mitr
i
Me ndele ev
(i
n Russi a)
arr
a nge d hi
s t
abl
e of
el
e me nts
( 50
eleme nt
s)
H e pu t
t
he el
eme nts
in
o rder
of
atomi c
ma s s
(like
John)
B ut inst
ead he l
eft
gaps t
o keep
elemt s
w i
th t
t
h e same pr
o pet
eis
in
t
he same
g roups…read more

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