Definitions Flashcards
Group
The column going down in the periodic table
Period
The row going along the periodic table
Covalent radius
A measure of the size of an atom
Trends in covalent radius going across a period and down a group
Across a period-decreases as nuclear charge increases
Down a group-increases as the number of electron shells increases
1st ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
Trends in first ionisation going across a period and down a group
Across a period-increases as nuclear charge increases
Down a group-decreases as there are more electron shells and increased screening effect
Electronegativity
A measure of the attraction which an atom involved in a bond has for electrons in the bond
Trends in Electronegativity across a period and down a group
Across a period-increases due to increased nuclear charge
Going down a group- decreases due to screening effect- shields the nuclear charge
Ionic formulae
Example:
Lithium oxide
Li2O
Lithium has a valency of 1 so has a 1+ charge and oxygen has a valency of 2 so has a charge of 2-
(Li+)2O2-
Pure covalent bonds
The bonds have no difference in Electronegativity
Vander Waals forces
LDFs and how the arise
Operate between all atoms and molecules
Formed by the electrostatic attraction between temporary dipoles and induced dipoles caused by the constant movement of electrons in atoms and molecules.
They are the weakest intermolecular force
They get stronger when there are more electrons in an atom/molecule
Bigger atoms/molecules have stronger LDFs
Permanent dipole-permanent dipole interactions and how they arise
The attraction between oppositely charged ends of polar molecules
Stronger than LDFs
Hydrogen bonding and how they arise
Found between molecules which contain highly polar bonds
They can form when hydrogen bonds with
Nitrogen
Oxygen
Fluorine
They are the strongest intermolecular force
When hydrogen bonds are present the melting and boiling points will be significantly higher
Polar molecules and how they arise
Molecules are polar when they have a permanent dipoles (one end of the molecule is permanently negative and one is positive)
Reduction
The gain of electrons
Oxidation
The loss of electrons
Redox reaction
When an oxidation and reduction reaction happen at the same time
Oxidising agents
A substance that brings about oxidation but it itself gets reduced (accepts electrons)
Reducing agent
A substance that brings about reduction but it get’s oxidised(donates electrons)
Factors affecting industrial process design
-availability,sustainability and cost of feedstock
-opportunities for recycling
-energy requirements
-product yield
Environmental considerations when designing an industrial process
-minimising waste
-avoiding use or production of toxic substances
-designing products which will be biodegradable of appropriate
Molar volume
Molar volume= volume/number of moles
Units- l mol-1
Percentage yield
%yield= actual yield/theoretical yield x 100
