Definitions Flashcards
What is metallic bonding?
Metallic bonding is the electrostatic force of attraction between positively charged ions and negatively charged delocalised electrons.
What are covalent bonds?
a shared pair of electrons electrostatically attracted to the positively charged nuclei of two non-metal elements.
What is covalent radius?
the measure of how large and individual atom is.
What is the first ionisation energy?
the energy involved in removing one mole of electrons from one mole of atoms in the gaseous state.
What is the screening effect?
The inner energy levels screen the nuclear charge from the outer electrons.
What is electronegativity?
Electronegativity is a measure of the attraction an atom involved in a bond has for the electrons of that bond.
What are intermolecular bonds?
Bonds between molecules.
What are intramolecular bonds?
Bonds inside/within molecules.
What is a pure covalent bond?
The two atoms have the same electronegativity and have no ionic character at all. Examples include diatomic elements.
What is a polar covalent bond?
When a shared pair of electrons are not shared equally. This is because one of the elements has a higher electronegativity than the other.
What is a dipole?
When one side of the atom becomes slightly negatively charged and the other side becomes slightly positively charged.
What are ionic bonds?
When there’s an uneven sharing of bonding electrons in covalent bonds. This is due to a large difference in electronegativity.
What are London dispersion forces?
They are the weakest type of intermolecular bonds.
How do London dispersion forces form?
They are caused by an uneven distribution of electrons within and atom making one side slightly negatively charged and the other slightly positively charged. This is known as an temporary dipole. The temporary dipole can move towards an atom causing an induced dipole which create London dispersion forces.
What are permanent dipole to permanent dipole interactions?
They are when polar molecules display attractions between the oppositely charged ends of the molecule. This intermolecular force is stronger than London dispersion forces.
What is Hydrogen bonding?
They occur when Hydrogen bonds with Oxygen, fluorine or nitrogen.
When are polar covalent bonds polar molecules?
When the shape of the molecules is asymmentrical.
When are polar covalent bonds non polar molecules?
When the shape of the molecule is symmetrical and the charges cancel each other out.
What is viscosity and what affects how viscous a molecule is?
Viscosity is the thickness of a liquid and can be affected by the number of hydroxyl groups are present. the greater the number of hydroxyl groups present the more viscous the molecule is.
What is solubility and what affects how soluble a molecule is?
Solubility is how much a substance will dissolve in a given volume of liquid. Polar molecules will dissolve in polar substances and non-polar molecules will dissolve in non-polar solvents. The number of hydroxyl groups present the more soluble the substance is. the greater the number of hydroxyl groups present, the more soluble the molecule.
What is a reducing agent?
Found at the top right hand side of the data book. It loses electrons to another element (it is oxidised). Note: The strongest reducing agents are the alkali metals in group 1.
What is an oxidising agent?
Found on the bottom left hand side of the data book. It gain electrons from other atoms (it is reduced).
What is a redox reaction?
When both oxidation and reduction takes place.
What are displacement reactions?
When metals higher in the electrochemical series displace lower metals from a solution in their ions
What does the collision theory state?
For a reaction occur the reactant must collide with the correct collision geometry and with enough energy to break existing bonds.
What is an activated complex?
An intermediate stage in which there is a high energy, unstable arrangement of atoms.
What are the factors affecting the rate of a reaction?
Temperature, concentration, pressure, particle size and the use of a catalyst.
What is activation energy?
Activation energy is the minimum energy required for the reaction to occur.
What happens to the activation energy when you add a catalyst?
Adding a catalyst lowers the activation energy causing the number of molecules with the minimum kinetic energy for the reaction to occur increase. This increases the number of successful collisions taking place.
What is enthalpy?
A measure of the chemical energy in a substance.
What is an exothermic reaction and what is it represented as?
When heat energy is released. The products will have less energy than the reactants because energy has been released. The enthalpy change for an exothermic reaction is always negative -
What is an endothermic reaction and what is it represented as?
What heat energy is absorbed. The products have more enthalpy than the reactants. The enthalpy change for an endothermic reaction is always positive +
What is the enthalpy of combustion?
The heat energy given out when one mole of a substance burn completely in oxygen. Always exothermic and are therefore negative.
What does Hess’s Law state that?
The enthalpy change for a chemical reaction is independent of the route taken meaning the enthalpy change for the overall reaction will be identical regardless of the number of steps taken
What is bond enthalpy?
The energy required to break one mole of bonds in a diatomic molecule.
What is mean bond enthalpy.
The average energy required to break one mole of bonds for a bond that occurs in a number of compounds
When is a reaction in dynamic equilibrium?
When rate of the forward reaction is equal to the rate of the reverse reaction.
What does Le Chatelier’s principle state?
If a system at equilibrium is subjected to any change, the system will adjust itself to counteract the applied change.
What happens when you increase the temperature of a equilibrium?
It favours the endothermic reaction.
What happens when you decrease the temperature of a equilibrium?
It favours the exothermic reaction.
What happens when you increase the pressure of a equilibrium?
It favours the side with the less gas volume.
What happens when you decrease the pressure of a equilibrium?
It favours the side with the greater gas volume.
What happens when the number of moles of gas are the same for equilibrium?
Because they have the same number of moles, changing the pressure does not favour either side of the equilibrium.
What does adding a catalyst do to the position of the equilibrium?
It has no effect on the position of the equilibrium- it does allow the equilibrium to be reached more quickly or at a lower temperature making the reaction more profitable.
What is a standard solution?
A solution of accurately known concentration.
What is the general formula for alkanes?
CnH2n+2
What is the general formula for alkenes?
CnH2n
What is the general formula for the cycloalkanes?
CnH2n
What is the general formula for alcohols?
CnH2n+1OH
What is the general formula for the carboxylic acids?
CnH2n+1COOH
What is molecular formula?
When only the number of atoms each element in one molecule of the substance.
What is full structural formula?
When all the atoms and all the bonds within molecules and shows exactly which is joined to which.
What is shortened structural formula?
Shows how the atoms are joined but only shows some, if any of the bonds.
What are addition reactions?
When the double bond of an alkene partially breaks when the reactant molecule attacks and adds on across.
What can be used to test for unsaturation and what is the reaction known as?
Bromine will rapidly decolourise alkenes. The addition of bromine is called bromination.
What are isomers?
Compounds with the same molecular formula but different structural formula.
What are alcohols?
Contain the hydroxyl functional group and the names end in ol.
What is a primary alcohol?
When the hydroxyl functional group is attached to a carbon atom with at least two hydrogen atoms attached.
What is a secondary alcohol?
When the hydroxyl group is attached to a carbon with only one hydrogen atom attached to it.
What is a tertiary alcohol?
When the hydroxyl group is attached to a carbon with no hydrogen atoms attached to it.
What is the name of an alcohol with two hydroxyl groups?
Diols
What is the name of an alcohol with three hydroxyl groups?
Triols
What do primary alcohols partially oxidise into?
Aldehydes (alkanals)