Transcript John DALTON - Atomic Theory and Periodic Table

Chemistry
The Atom
© SSER Ltd.
Ancient Greeks were the first to come up with the idea of atoms.
Democritus
suggested that all
matter was made of
tiny indivisible
particles called
atoms. (Greek “atoma”)
Democritus
John DALTON
Ha Ha! You can’t
break me!!!!
An indestructible “Dalton” atom
J.J. THOMPSON
Earnest Rutherford
In 1910, Earnest Rutherford carried out
experiments in which particles were fired at a
thin sheet of gold.
Rutherford expected all of the particles to
pass straight through...
Earnest Rutherford
He concluded that the atom consisted of a central nucleus, which
contained most of the atom’s mass, surrounded by the electrons.
He also predicted the existence of neutrons in the nucleus.
Ernest RUTHERFORD
Ernest RUTHERFORD
Rutherford could not explain why the
negative electron didn’t fall into the
positive nucleus and destroy the atom.
?
I think I can
help!
Neils Bohr
Neils BOHR
He showed that the electrons inhabit
discrete energy levels surrounding the
nucleus
When the atom was “excited” the electron could “jump”
to a higher level.
When the electron came back down, it released energy
in the form of light.
Elements emit a particular
wavelength or colour as
electrons jump from one shell
to another
Eg. Neon light
Neils Bohr: 1885 - 1962
Element 107 on the Periodic
Table is called Bohrium (Bh)
Electron Levels (Shells)
The first electron level (shell) can hold up to 2 electrons.
The second electron level (shell) can hold up to 8 electrons.
The third electron level (shell) can hold up to 18 electrons.
= Neutron
= Proton
= Electron
The Carbon Atom
Mass Number
Atomic Number
= 6 xNeutrons
= 6 xProtons
12
C
6
= 6 x Electrons
In the 1920’s things changed!
Although Bohr’s idea of energy levels
was still accepted, his idea of planetary
orbits for electrons was rejected!
REJECT ! !
So……
What’s Next???
????????????
Erwin Schrödinger
He proposed the electrons appear as “clouds”.
The electron has a high probability of being located
within this cloud or region surrounding the nucleus.
1887-1961
Subshells
 Each energy level/shell (n) contains one or
more subshells – s, p, d, and f
 Each subshell contains an electron orbital
where up to 2 electrons can most likely be
found
S Orbitals
1s
2s
3s
Three p Orbitals
px
py
pz
p subshell can hold a maximum
of 6 e-’s in p orbitals
d orbitals – max 10e-’s
Timberlake LecturePLUS 2000
Writing Electron Configurations
H
1s1
He
1s2
Li
1s2
2s1
C
1s2
2s2
2p2
S
1s2
2s2
2p6
3s2
3p4
Learning Check
Indicate which configuration is correct for
potassium. Explain.
A.
1s22s22p63s1
B.
1s22s22p63s23p6
C.
1s22s22p63s23p64s1
D.
1s22p83s1
E.
1s22s22p63s23p7
Solution
Potassium:
A. 2, 2, 8, 5
B. 2, 8, 3
C. 2, 8, 5
D. 2, 6, 7
Learning Check
Using the periodic table, write the complete
electronic configuration for each:
A. Cl
B. Sr+2
C. I
Solution
Using the periodic table, write the complete
electronic configuration for each:
A. Cl
B. Sr+2
C. I
Learning Check
A.
The final two notations for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The final three notations for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2
Solution
A.
The final two notations for Co are
3) 4s2 3d7
B. The final three notations for Sn are
2) 5s2 4d10 5p2
Learning Check
A. Number of electrons in a p orbital
1) 1e
2) 1e or 2e
3) 3e
B. Number of orbitals in a p subshell
1) 1
2) 2
3) 3
C. Number of orbitals in 4d subshell
1) 1
2) 3
3) 5
D. Number of electrons (maximum) in a 3d
subshell
1) 2e
2) 5e
3) 10e
Solution
A. Number of electrons in a p orbital
2) 1e or 2e
B. Number of orbitals in a p subshell
3) 3
C. Number of orbitals in 4d subshell
3) 5
D. Number of electrons in a 3d subshell
3) 10e