CHEM1100 Study Guide - Midterm Guide: Photon, Electron Affinity, Vsepr Theory
Module 1 important concepts !
Atomic symbol
Z = atomic
number
A = mass number
X = atomic symbol
N = charge of the atom
Mass = protons + neutrons
History
Leucippus and Democritus (490 BC)!
•introduced the idea that matter is made up of atoms, which are indivisible - the joint founders of
atomic theory. !
•Leucippus stated that atoms are "imperceptible, individual particles that differ only in shape and
position”
The photoelectric effect
•Researchers found that electrons could be knocked off a plate and onto a detector!
•Different metals needed different wavelengths of light to get the electron to move !
•Light (electromagnetic radiation) exhibits wave and particle properties !
•Each particle of light is a “quanta” of energy which is a discrete set of energy!
Energy levels
•electrons can absorb energy !
•It also absorbs quantised values of energy !
•
The waves have to be a certain type of waves!
They have physical parameters they cannot cross !
Mass is defined by the International Prototype
Kilogram of platinum and iron. The error should
be zero but small changes are being found. !
Australia’s kilo is made of silicone. !
find more resources at oneclass.com
find more resources at oneclass.com
Shielding and penetration
The effect of shielding and penetration is the following:!
The lewis structure
The lewis structure for organic compounds is drawn like this:!
!
Valence Shell Electron Pair Repulsion Theory (VSEPR)
The principle of minimising electron repulsion by placing electron pairs as far apart as possible. !
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The error should be zero but small changes are being found. Energy levels: electrons can absorb energy, it also absorbs quantised values of energy. The waves have to be a certain type of waves. The e ect of shielding and penetration is the following: The lewis structure for organic compounds is drawn like this: The principle of minimising electron repulsion by placing electron pairs as far apart as possible. Electron affinity is defined as the change in energy (in kj/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. The energy required to remove an electron completely from a species (in the gas phase) orbitals, subshells and principal shells. Things to remember: even though electrons reside in their own sub-shell, they can always accompany high sub-shells if excited.
