chy 116 atomic structure
TRANSCRIPT
![Page 1: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/1.jpg)
Quantum Mechanical Model of the Atom
![Page 2: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/2.jpg)
2
• Many scientists contributed to the development of the quantum mechanical model of the atom.– Bohr– Planck– DeBroglie– Heisenberg– Schrodinger– Pauli
![Page 3: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/3.jpg)
3
What was already known..
• Early 1900’s…believed that– Energy is quantized– Electrons have both wave and matter
properties– Electrons can be at a variety of specific
energy levels in an atom• Energy levels are called orbits
– Proposed that electron had both wave and matter properties
![Page 4: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/4.jpg)
4
Schrodinger & deBroglie
• S & deB pictured the electron bound to the atom in a standing wave– Standing vs. traveling waves
• See page 301
![Page 5: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/5.jpg)
5
Schrodinger
• Sch.. Proposed that electrons move around the nucleus in standing waves– Each orbit represents some whole number
multiple of a wavelength– Schrodinger analyzed the hydrogen data
based on the assumption that the electrons behaved as standing waves.
![Page 6: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/6.jpg)
6
Schrodinger
– Schrodinger’s equation takes into account:• The position of the electron in 3D space (its x,y,z
coordinates)• Potential energy of the atom due to the attraction
between electrons and protons• Kinetic energy of the electron
![Page 7: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/7.jpg)
7
Schrodinger
• Schrodinger’s equation has many solutions– Each solution is called a wave function ()
and is correlated to a specific amount of energy
• Each wave function is more commonly called an orbital.
![Page 8: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/8.jpg)
8
Orbitals
Each solution to Schrodinger’s equation describes a specific wave function () /orbital– The square of a wave function, ()2,
generates a probability distribution for an electron in that orbital
• Also called an electron density map for a given orbital
![Page 9: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/9.jpg)
9
Orbitals
• Orbitals are regions in space where an electron is likely to be found– 90% of the time the electron is within the
boundaries described by the electron density map
– The exact path of an electron in a given orbital is not known!
![Page 10: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/10.jpg)
10
Heisenberg
• Heisenberg uncertainty principle states that we cannot know both the position and the momentum of an electron at the same time.– Therefore, we do not know the exact path of
the electron in an orbital.
![Page 11: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/11.jpg)
11
Orbitals
• Schrodinger’s equation and the associated electron density maps, allow us to describe the energy, size, and shape of orbitals.– The lowest energy solution to Sch..’s equation
for an electron in a hydrogen atom describes what is known as the 1s orbital.
• See pages 306/307
![Page 12: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/12.jpg)
12
Describing Orbitals
• Use quantum numbers to describe orbitals. A given orbital can be described by a set of 3 quantum numbers:
1. Principal quantum number (n)
2. Angular momentum quantum number (l) 3. Magnetic quantum number (ml)
![Page 13: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/13.jpg)
13
Principal Quantum Number (n)
• (n) describes the size and energy of the oribital– Possible values: whole number integer
• 1, 2, 3, …
– As “n” increases so does the size and energy of the orbital
![Page 14: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/14.jpg)
14
Angular momentum quantum number (l)
• (l) is related to the shape of the orbital– Possible values: (l) is an integer between 0
and n-1– Each (l) value is also assigned a letter
designation
![Page 15: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/15.jpg)
15
Angular momentum quantum number (l)
(l) Value Letter Designation
0 s
1 p
2 d
3 f
![Page 16: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/16.jpg)
n Possiblel values
Designation
1 0 1s
2 01
2s2p
3 012
3s3p3d
4 0123
4s4p4d4f
16
![Page 17: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/17.jpg)
17
Magnetic quantum number (ml)
• (ml) is related to the orientation of the orbital in 3-D space– Possible values: - l to + l
![Page 18: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/18.jpg)
18
Magnetic quantum number (ml)
• Consider the p orbital…it has an l value of 1 and thus the possible ml values are -1, 0, +1– These 3 ml values correspond to the 3
possible orientations of the p orbital
![Page 19: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/19.jpg)
19
Ml and Orbitals
l ml # orbitals
0 (s) 0 1
1 (p) -1, 0, 1 3
2 (d) -2, -1, 0, 1, 2 5
3 (f) -3, -2, -1, 0, 1, 2, 3 7
![Page 20: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/20.jpg)
20
Quantum Number Summary
• See page 304 and board.– A set of 3 quantum numbers describes a
specific orbital• Energy and size - n• Shape - l
• Orientation – ml
![Page 21: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/21.jpg)
21
4th Quantum Number!
• A 4th quantum number was added to describe the spin on a given electron.– Called the electron spin quantum number - ms
• Possible values: +1/2 and -1/2
![Page 22: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/22.jpg)
22
More on electron spin.
• Each orbital can hold a maximum of 2 electrons of opposite spin.
• Pauli exclusion principle states that no two electrons in an atom can have the same set of 4 quantum numbers
![Page 23: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/23.jpg)
Summary
• Three quantum numbers describe a specific orbital– Energy and size, shape, and orientation
• Four quantum numbers describe a specific electron in an atom
23
![Page 24: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/24.jpg)
24
7.9 Polyelectronic atoms
• The Schrodinger model was based on H and works in principle for atoms with more than one electron.– The shapes and possible orientations of the
hydrogen based orbitals holds true for polyelectronic atoms.
– However, the size and energy of the orbitals in polyelectronic atoms differ from those calculated for hydrogen.
![Page 25: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/25.jpg)
25
Polyelectronic Atoms
• In general, find that in a given principal quantum number (n) – S is lower energy than p, which is lower
energy than d…..• s < p < d < f
– Already know that 1s < 2s < 3s… and 2p < 3p < 4p…. (in terms of size and energy)
![Page 26: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/26.jpg)
26
7.11 The Aufbau Principle
• Putting electrons in to orbitals…– Aufbau means “building up” in German– Electrons always enter the lowest energy
orbital with room
![Page 27: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/27.jpg)
27
Hund’s Rule
• The orbitals of a given sublevel (e.g. p, or d, or f) are degenerate (of the same energy).
• The lowest energy state occurs with the maximum number of unpaired electrons.– Meaning…..electrons enter an empty orbital
of a given sublevel before pairing up.
![Page 28: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/28.jpg)
28
Goals
• To be able to write for any atom:– Electron configuration– Box/energy diagram– Lewis dot symbol
• State the quantum numbers for each electron in an atom.
• To relate the electron configuration of an atom to its location on the periodic table and its properties.
![Page 29: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/29.jpg)
29
Goals Elaborated
• Electron configuration – shows the number of electrons in each sublevel– Format: 1s22s22p4 or [He] 2s22p4
• Box/energy diagram – shows electrons as arrows and each orbital as a box. Electrons of opposite spin are indicated by up and down arrows.– Format:
![Page 30: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/30.jpg)
30
Goals Elaborated
• Lewis Dot Symbol – shows valence electrons as dots around the symbol for the atom– Maximum of 2 electrons per side of the
symbol– Valence electrons are all of the electrons in
the highest occupied principle quantum level (n)
– Format:
![Page 31: Chy 116 Atomic Structure](https://reader033.vdocument.in/reader033/viewer/2022061108/54505430b1af9f05098b4c14/html5/thumbnails/31.jpg)
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s…
31