Chapter 6 Speaking of molecules

catalyst

A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up, or catalyze.

chemical equation

A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side.

synthesis

A synthesis reaction or direct combination reaction is a type of chemical reaction in which two or more simple substances combine to form a more complex product. The reactants may be elements or compounds. The product is always a compound.

lewis dot symbol

Lewis symbols use dots to visually represent the valence electrons of an atom. The Lewis symbol for an atom depicts its valence electrons as dots around the symbol for the element. In covalent molecules, atoms share pairs of electrons in order to achieve a full valence level.

product

Products are the species formed from chemical reactions. During a chemical reaction reactants are transformed into products after passing through a high energy transition state.

bonded pair

The electron pair represented by the line is called a bonding pair; the three other pairs of electrons on the chlorine atom are called lone pairs and play no direct role in holding the two atoms together.

octet rule

The octet rule is a chemical rule of thumb that reflects observation that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

HONC 1234 rule

Within most molecules, hydrogen makes one bond, oxygen makes two bonds, nitrogen makes three bonds, and carbon makes four bonds. The bonds in a structural formula are represented by lines.

triple bond

a chemical bond in which three pairs of electrons are shared between two atoms.

double bond

a chemical bond in which two pairs of electrons are shared between two atoms.

Molecular formula

a formula giving the number of atoms of each of the elements present in one molecule of a specific compound.

structural formula

a formula that shows the arrangement of atoms in the molecule of a compound.

functional group

a group of atoms responsible for the characteristic reactions of a particular compound.

lone pair

a lone pair refers to a pair of valence electrons that are not shared with another atom and is sometimes called a non-bonding pair. Lone pairs are found in the outermost electron shell of atoms.

chemical reaction

a process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction.

reactant

a substance that takes part in and undergoes change during a reaction.

Lewis dot structure

diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

isomer

each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.