Term | Definition |
A Compound | A substance that is made up of two or more elements combined together chemically. |
The Octet Rule | The octet rule states that when bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost shell. |
The main exceptions of the octet rule | Transition metals don't follow the rule and elements near helium in the periodic table ten to have two electrons in their outer shell rather than eight. |
An ion | is a charged atom or group of atoms. |
An ionic bond | force of attraction between oppositely charged ions in a compound. |
A transition metal | is one that forms at least one ion with a partially filled d-sublevel |
A molecule | is a group of atoms joined together. It is the smallest particle of an element or compound that can exist independently. |
The valency of an element | the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines. |
Electronegativity | relative attraction that an atom in a molecule has for a shared pair of electrons in a covalent bond. |
The result of different electronegativity values in bonding | An electronegativity difference greater than 1.7 indicates ionic bonding in a compound. An electronegativity difference of 1.7 or less indicates covalent bonding in a compound. |
Van Der Waals | weak attractive forces between molecules resulting from the formation of temporary dipoles. |
Dipole dipole forces | forces of attraction between the negative pole of one molecule and the positive pole of another. |
Hydrogen bonds | are particular types of dipole dipole attractions between molecules in which hydrogen atoms are bonded to nitrogen, oxygen or fluorine. The hydrogen atom carries a partial positive charge and is attracted to the electronegative atom in another molecule. |
The names for the number of carbon atoms in a hydrocarbon | Meth, Eth, Prop, But, Pent, Hex, Hept, Oct, Non, Dec |
A homogulus Series | Compounds of uniform chemical type
Showing gradations in physical properties
General formula for its members
Each member has a similar method of preparation
Each member differs from the previous by a CH2 unit. |
Structural Isomers | compounds with the same molecular formula but different structural formulas. |
An aliphatic compound | an organic compound that consist of open chains of carbon atoms and closed chain compounds (rings) that resemble them in chemical properties. |
Aromatic compounds | Compounds that contain a benzene ring structure in their molecule. |
Fractional distillation | a process that involves heating crude oil and seperating the various mixtures on the basis of their boiling points. |
Refinery gas and a use | C1- C4 used for lighter fluid |
Petrol and a use | C5 - C10 used as fuel for some cars |
Naphtha and a use | C7 - C10 used for solven |
Kerosine (Parrafin)and a use | C10 - C14 used as fuel for planes |
Diesel oil (gas oil) | C14 - C19 used for cars |
Lubricating oil and a use | C19 - C35 used as a lubricant to reduce the wear of engines |
Fuel Oil and a use | C30 - C40 used a fuel for power stations |
Bitumen and a use | a chain greater than C35 and used for the tar on roads |
Octane Number | the measure of the tendancy of the fuel to resist knocking. |
Octane number of 2,2,4 trimethylpentane | 100 |
Octane number of heptane | 0 |
Four ways to increase the octane number of petrol | 1) Isomerisation
2) Catalytic Cracking
3)Reforming (Dehydrocyclisation)
4) Adding oxygenates |
Describe isomerisation | changing straight chains into isomers by branching |
Describe catalytic cracking | breaking down of long chain hydrocarbon molecules into short chain molecules for which there is a greater demand. |
Describe Reforming | Using catalysts to form ring compounds. |
Adding oxygenates | Adding oxygen to the hydrocarbons. |
Heat of reaction | Heat of change when the numbers of moles of reactants indicated in the balanced equation for the reaction react completely |
Heat of combustion of a substance | the heat change when one mole of the substance is completely burned in excess oxygen. |
The kilogram calorific value | the heat energyproduced when 1kg of the fuel is completely burned in oxygen. |
Bond energy | the energy required to break one mole of covalent bonds and to separate the neutral atoms completely from each other. |
Heat of neutalisation | the heat change when one mole H+ ions from an acid reacts with one mole of OH- ions from a base. |
An Element | a substance that cannot be split up into simpler substances by chemical means. |
A Triad | a group of three elements with similar chemical properties in which the atomic weight of the middle element is approximately equal to the average of the other two. |
Newland's Octaves | groups of elements arranged in order of increasing atomic weight, in which the first and the eight element of each group have similar properties. |
Mendeleev's Periodic Law | When elements are arranged in order of increasing atomic weight (Relative atomic mass), the properties of the elements vary periodically. |
Mendeleev's Table is different to Newland's table forr two reasons. State them. | 1: He left gaps in his table to make the elements fit into the proper column
2:He had to reverse the order of elements in order to make them fall into groups of elements with similar properties. |
The atomic number | number of protons in the nucleus of that atom |
Modern periodic table | arrangement of elements in order of increasing atomic number. |
When elements are arranged in order of increasing atomic number... | the properties of the elements vary periodically. |
Mass number | the sum of the number of protons and neutrons in the nucleus of an atom of that element. |
Isotopes | atoms of the same element that have different mass numbers due to the different number of neutrons in the nucleus. |
Relative Atomic Mass | 1: The average of the mass numbers of the isotopes of the element
2: As they occur naturally
3: Taking their abundances into account
4:Expressed on a scale in which the atoms of the carbon-12 isotope have a mass of exactly 12 units. |
The Aufbau Principle states that... | when building up the electronic configuration of an atom in its ground state, the electrons occupy the lowest available energy level. |
Hund's Rule of Maximum Multiplicity states that... | when two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs. |