Topic : Compounds and reactions

Chapter 1 : Introduction to molecules and compounds

• A molecule is a chemical unit capable of independent existence
• A molecule can consist of one or more atoms
• Molecules containing one atom are monatomic
• Molecules containing two atoms are diatomic
• A compound is a molecule containing two or more chemically bonded elements
• Ionic bonding occurs when two or more elements combine and there is a respective loss and gain of one or more electrons
• A cation is a positively charged atom that has lost one or more electrons in an ionic bond
• An anion is a negatively charged atom that has gained one or more electrons in an ionic bond
• A covalent bond is one in which two or more elements combine by sharing one or more pairs of electrons
• A covalent bond usually occurs between two non-metals

Chapter 2 : Introduction to reactions

• The Law of the Conservation of Matter/Mass states that matter is not created or destroyed
• Reactants are the starting ingredients for a chemical reaction
• A chemical reaction is the process by which elements change to make new substances
• A physical change occurs when a substance changes shape or form but retains its chemical structure
• A chemical change occurs when a substance changes its chemical structure, leaving a new substance or substances

Chapter 3 : Understanding formulae

• A subscript number following an element indicates the number of atoms in a molecule
• Chemical formulae indicate the exact ratio of elements in a particular compound
• Properties of a compound depend on the proportion of elements that it contains
• Ions have their charge written in superscript after the chemical unit. If there is more than one ion, the number comes before the charge
• Polyatomic ions are ions containing more than one atom
• Radicals are polyatomic ions, groups of atoms with a charge
• To indicate more than one radical in a compound, use parentheses around the radical and a subscript number
• When more than one type of compound results from a chemical reaction containing the same substances, a Roman numeral is placed in parentheses following the element whose valency differs

Chapter 4 : Naming compounds

Chapter 5 : Chemical equations

• Ionic compounds will generally form so that the compound is stable and the valency charges balance
• Radicals operate as a group in a formula
• You can find the formula of a covalent compound if you know the combining power of the non-metals involved
• Chemical equations are formulae showing the reactants and its products
• The -> symbol indicates 'reacts to form'
• Balancing an equation requires the reactants and the products to have the same mass
• A coefficient is a numeral denoting a multiple of any molecule

Chapter 6 : Acids and bases

• An acid is a sour substance that releases hydrogen ions in a chemical reaction
• A base is a bitter substance that accepts hydrogen ions in a chemical reaction
• An alkali is a soluble base containing hydroxide ions
• Strong substances readily transfer ions in a chemical reaction
• Weak substances do not readily lose or gain ions in a chemical reaction
• Concentrated substances have a high substance to water ratio
• Dilute substances are dissolved in a lot of water
• Indicators show the presence of an acid or base
• The pH scale measures acidity/alkalinity using 14 increments
• Acidic substances have a low pH