Chemistry for Biology Students (CHEM0010) Notes - Structure, Bonding and Self-Assembly of Biological Structures
17 views 0 purchase
Course
Chemistry for Biology Students (CHEM0010)
Institution
University College London (UCL)
Explore foundational chemistry with these specialized notes tailored for Year 1 students in the Chemistry for Biology Students (CHEM0010) module at University College London. Dive into the intricacies of structure, bonding, and self-assembly of biological structures, deciphering key concepts like a...
A1: Structure of the Atom, Electrons and Orbitals
A1: Structure of the Atom, Electrons and Orbitals
Atomic structure
o Subatomic particles
Electron – mass = 0, charge = -1, spin = 0.5
Proton – mass = 1, charge = +1, spin = 0.5
Neutron – mass = 1, charge = 0, spin = 0.5
o Nucleus
Proton + neutron
Atomic number (Z) = number of protons in the nucleus
Relative atomic mass (Mr) = number of protons + neutrons
o Element
Fixed number of protons
Isotope = varying number of neutrons
Mass spectrometer – measures mass of isotopes
o Shows peaks for mass of each isotope + relative abundance
Electron
o Electron configuration – determines chemical reactivity
Occupy orbitals = have fixed energy values
o Rules:
Aufbau’s ‘building up’ principle – lowest energy orbitals are occupied first
Pauli principle – only 2 electrons occupy each orbital
o Electrons have – wave-particle duality
Wave-particle duality – a quantum object is both a wave and a particle
Electrons can be described by a wave function:
o Wave function – mathematical distributions of electrons in terms of position
and time
Heisenberg Uncertainty Principle
Position and momentum cannot simultaneously be determined
o The energy of an electron is known (due to spectroscopy) > therefore the
position is unknown
o Orbital – region where an electron is most probably located
Quantum numbers – describe orbital shapes and size (electrons have 4 quantum numbers)
Principle quantum number (n) –1 st quantum number (shell)
o Shell (n)
Subshell – within each shell
o How big the orbital is / how far an electron occupying it is from the nucleus
Angular quantum number (I) – 2nd quantum number (shape of orbital)
o I = 0, … n-1 (n = principle quantum number)
o Tells you the shape of the orbital (s, p, d, f)
S: I = 0
Each s subshell – has 1 s orbital
P: I = 1
Each p subshell – has 3 p orbitals
D: I = 2
Each d subshell – has 5 d orbitals
Magnetic quantum numbers (m1) – 3rd quantum number (orientation of orbital)
o m1 – -I, … +I
E.g. if I = 1, m1 = -1, 0, +1
o Tells you the orientation of the orbital
x = -1
, A1: Structure of the Atom, Electrons and Orbitals
y=0
z = +1
Spin quantum number (ms) – 4th quantum number (spin)
o Electrons have a spin – property of electron is related to angular momentum
ms = -0.5, +0.5
ms – +0.5 = clockwise rotation
ms – -0.5 = anticlockwise rotation
Pauli exclusion principle – no 2 electrons in an atom can have the same 4 quantum numbers
Max 2 electrons can share each orbital
o Same value of n
o Same value of I
o Same value of m1
o Different (ms) = different spin
Summary of quantum numbers
n (shell) I (shape) Orbital notation m1 (orientation) Orbital names
1 0 1s 0 1s
2 0 2s 0 2s
1 2p -1, 0, +1 2px, 2py, 2pz
3 0 3s 0 3s
1 3p -1, 0, +1 3px, 3py, 3pz
2 3d -2, -1, 0, +1, +2 3dxy, 3dyz, 3dzx,
3dx2-y2, 3dz2
Shape of orbitals (I)
o Wave functions:
Order of energies of orbitals – orbital further from
the nucleus = higher energy
Node = 0% chance of finding an electron
o More nodes = higher energy
Radial distribution function – how the probability of
finding an electron varies with distance from the
nucleus
1s2 electrons shield 2s1 electron from the
nuclear charge
o But: 2s radial distribution function
has a hump closer to the nucleus
than 1s
Resulting in an energy boost
for 2s1 = can penetrate than
1s2 orbital + spends more
time closer to the nucleus
2s1 closer to nucleus
= experiences a
stronger attraction –
energy is lowered
2p6 electrons radial distribution function = low probability of finding electron close
to nucleus
o 2p6 electrons do not penetrate 1s2 orbital as much = better shielded from
nuclear charge
Higher energy
Hund’s rule of maximum multiplicity
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sujansathiendran. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.63. You're not tied to anything after your purchase.
