Transcript Studio 3a: Atomic Hotel

Studio 3a: Atomic Hotel
1913: Bohr Model
A planetary model: the electrons orbit around protons and
neutrons that occupy a central space.
Different electron levels hold different numbers of electrons.
The 1st level holds 2 electrons
The 2nd level holds 8 electrons
The 3rd level holds 18 electrons
The farther the electron level is from the “nucleus” of the
atom, the more energy it has. The electrons usually fill
the electron levels from closest to furthest out.
Bohr Model Flaws
Ineffective explanation for bonding between
atoms.
Little ability to predict molecular shapes.
Could not predict how many bonds a
particular atom is likely to form
Atomic Orbital: Today’s
Working Model of an Atom
Atomic orbital theory places the electrons in
specific regions of space called orbitals.
These orbitals can be mathematically
derived through quantum mechanics.
Use the Atomic Hotel exercise (I-IV) in your
coursepack to explore how electrons occupy
atoms in accordance with quantum mechanics.
Analogies to Atomic Hotels
• Floors = shells
• Rooms = orbitals
Floors = Shells
• Every atom has many shells around it.
• Each shell is spherical and fully encompasses
the nucleus….More like an onion (3D) than a
solar system or hotel floor (2D)
• Shells represent the distance from the
nucleus...they get larger as they go outward.
Pictures from: www.gojskoj.se/ arkiv03a.asp?id=20030305 and
http://mymiraclebaby.com/Merchant2/graphics/00000001/stack-cups.gif
Shells (n)
•Shells are named using integers
numbers (n). The innermost shell is 1,
the next is 2, etc.
•Each shell (floor) is made of up or one
or more types of orbitals (rooms)
Rooms = Orbitals
• Orbitals are representations of the
probability that the electron/s that occupy it
will be in the space they defined.
• Orbitals of different shapes (different room
layouts) are distinguished with
letters (s, p, d, f...)
or numbers (0, 1, 2, 3…) (room layout l)
S Orbitals (l = 0)
• The simplest orbital is spherical and called
an s orbital
The First Shell
• The innermost shell (1) only contains an s
orbital.
1s
Picture from: www.tomchemie.de/ Atombau1.htm
p Orbitals (l = 1)
• Rather than being a sphere, the "p" orbital
has two lobes pointed in opposite direction
away from the nucleus.
• One p orbital points along each the x, y, and z
axis.
• There are three p orbitals in every shell
except the first.
The Second Shell
The second shell contains an s type orbital
as well as a new kind of orbital called a "p"
orbital.
2py
2s
2pz
2px
The First Two Shells
Picture from and more info on How Atoms Work
d Orbitals (l = 2)
• There are 5 types of d orbitals. Four of
the five have four lobes at 90o to one
another. The fifth looks like a donut
around a p-orbital
Image from: HMChem
The Third Shell
• The 3rd shell has:
– 1 s orbital (3s)
– 3 p orbitals (3px, 3py, 3pz)
– 5 d orbitals (3dxy, 3dyz, 3dxz, 3dx2-y2, 3dz2)
f orbitals
• f-orbitals
have 6 lobes
and are very
challenging
to envision
Image from: HMChem
The Fourth Shell
• The 4th shell has:
– 1 s orbital (4s)
– 3 p orbitals (4px, 4py, 4pz)
– 5 d orbitals (4dxy, 4dyz, 4dxz, 4dx2-y2, 4dz2)
– 7 f orbitals
• How many electrons do each of the first
four shells hold?
Atomic Hotel and the
Periodic Table
The energy of the orbital
depends on its electron
shell level and its shape.
Aufbau principle: orbitals
filled in order of
increasing energy.
Pauli Exclusion Principle: at most
two electrons can be assigned to any
one atomic orbital and these two
electrons must have opposite spins
Hunds rule: Electrons pair only after
each orbital in a set of the same
shaped orbitals at the same energy
level is occupied by a single electron
Quantum Numbers
n –shell
l – type of orbital (orbital shape)
ml –specific orbital orientation
ms – specific electron of the pair in each
orbital
Identifying electrons: Quantum
Numbers
Hotel
H
Li
Quantum Numbers
Assign quantum numbers to the electrons of
Ne:
l
ml ms
n