Chemical Bonding

Ionic Bonding Content Common Complex Cations and Anions (Examples) Ion name Chemical Formula Cation/Anion Sulfate 𝑆𝑂4 2− Anion Nitrate -3NO Carbonate 𝐶𝑂3 2− Hydroxide −OH Dichromate (VI) 𝐶𝑟2𝑂7 2− Manganate 𝑀𝑛𝑂4 2− Phosphate 𝑃𝑂4 3− Silver 𝐴𝑔+ Cation Zinc 𝑍𝑛2+ Chromium 𝐶𝑟3+ Tin 𝑆𝑛2+ Aluminium 𝐴𝑙3+ Copper 𝐶𝑢2+ General Rules when writing Chemical Formulae (Ionic Compounds) Rule no. Rule 1 A compound made from 2 elements has a name that ends with -ide 2 The oxidation state of an ion will tell the charge of the ion 3 A compound that contains a polyatomic ion containing oxygen has a name ending in - ate, however when that anion has one less Oxygen atom, it ends with -ite 4 Metallic element first, then non-metallic element (Except for Organic Compounds) 5 A compound that has more than 1 polyatomic ions must have brackets between it Sample ‘Dot-and-Cross’ Diagram for an Ionic compound Structure of Physical Properties of Ionic Compounds Structure of Ionic Compounds - Called giant ionic lattice structures - 3 dimensional and held in place by ionic bonds - Held together tightly as oppositely charged ions attract one another strongly

Physical Properties of Ionic Compounds No. Property Explanation 1 Most ionic compounds have high melting points and high boiling points - Ionic compounds have very strong electrostatic forces of attraction between oppositely charged ions - A lot of thermal energy is required to overcome these electrostatic forces of attraction between oppositely charged ions 2 Ionic compounds are usually soluble in water and insoluble in organic solvents 3 Ionic compounds are good conductors of electricity when molten or in aqueous solution - There must be free and mobile ions in order for the compound to conduct electricity. - In aqueous solution/molten state, the cations and anions are free and mobile and can act as charge carriers and can carry electrical charge - In solid state, there are no free-moving ions to conduct electricity since the ions are vibrating in fixed positions

Covalent Bonding Sample ‘Dot-and-Cross’ Diagram of a Covalent Molecule Common prefixes for naming compounds Prefix Number of atoms mono 1 di 2 tri 3 tetra 4 Structure and Properties of Covalent Substances Section A: Structure and Properties of Simple Covalent substances - Held by strong Intramolecular forces of attraction - Held by weak Intermolecular forces of attraction Properties of Simple Molecular Substances Note: Do not confuse yourself, intra- means within. And they are not weak Covalent bonds are in fact the strongest bonds. Inter- means between molecules No. Property Explanation 1 Low melting and boiling points - Between molecules, they are held by weak intermolecular forces of attraction - Little Thermal Energy is required to overcome these weak intermolecular forces of attraction between molecules - Therefore, they have low melting and boiling points 2 Insoluble in water but soluble in organic solvents - However, a certain group of compounds called hydrogen halides can dissolve in water forming acids (See Acids and Bases Notes) 3 Do not conduct electricity in the solid, liquid or gaseous state - Simple Covalent Molecules do not have any mobile ions or delocalized electrons that can act as charge carriers to carry electrical charge

Section B: Structure and Properties of Giant Molecular Structures (Macromolecules) Structure of Giant Molecular Structures - Giant network of atoms covalently bonded together - Examples include: Boron Nitride, Silicon Dioxide, Diamond, and Graphite - Diamond and Graphite are allotropes (different forms of the same element) of carbon Properties of Giant Molecular Structures No. Property Explanation 1 Very high melting and boiling points - A giant molecular structure consists of a large number of atoms that are held together by strong covalent bonds - To melt or boil these substances, these strong covalent bonds must be broken. - A lot of thermal energy is required to break these covalent bonds 2 Do not conduct electricity (Except for Graphite) - All valence electrons in giant molecular structures are used for bonding (except graphite) - Therefore, no free and mobile delocalized electrons that can act as charge carriers to carry electrical charge 3 Insoluble in both water and organic compounds - Water cannot weaken the strong covalent bonds to attract the atoms to therefore dissolve it Diamond – Its Special Properties and Structure No. Property Explanation based on its Structure 1 Hard and has a high melting point - Each carbon atom is covalently bonded to 4 other carbon atoms, forming a tetrahedral arrangement - A lot of thermal energy is needed to break these strong covalent bonds between Carbon atoms 2 Does not conduct electricity - All valence electrons in of carbon atoms used in bonding - No free and mobile delocalized electrons that move throughout the structure that can act as charge carriers to carry electrical charge Graphite – Its Special Properties and Structure No. Property Explanation based on Structure

1 High Melting and Boiling Point - Each carbon atom is covalently bonded to three other atoms, in a hexagonal arrangement in layers - A lot of thermal energy is required to break these strong covalent bonds 2 Soft and Slippery - Layers of carbon atoms are held loosely by weak intermolecular forces of attraction - These layers of carbon atoms can slide over one another when a force is applied. 3 Conducts Electricity - Each carbon atom has one valence electron that is not used to form covalent bonds - These delocalized electrons can move freely along the hexagonal layers and act as charge carriers, therefore able to carry electrical charge Silicon Dioxide No. Property Explanation based on Structure 1 High melting and boiling point - Each Silicon atom is bonded to four oxygen atoms and each oxygen atom is bonded to two silicon atoms, forming a tetrahedral arrangement - A lot of thermal energy is needed to break these strong covalent bonds 2 Does not conduct electricity - All valence electrons are used for bonding - No free and mobile delocalized electrons that can act as mobile charge carriers to carry electrical charge Metallic Bonding Physical Properties of Metals No. Property Explanation

1 Good Conductors of electricity - Presence of free and mobile delocalised electrons to carry electrical charges 2 Good Conductors of Thermal Energy - Due to the movement of the delocalized electrons within the metal lattice - Thermal Energy is transferred easily by the delocalized electrons in the structure 3 Usually have high densities, melting points, and boiling points - Atoms in a metal are packed tightly and held together by strong metallic bonds - Large amount of energy required to break these strong metallic bonds between positively charged metal cations and sea of delocalised electrons 4 Malleable and ductile - When a force is applied, the layers of metal atoms can slide over each other easily in their orderly arrangement Alloys Why are alloys used? No. Reason Example 1 To make metals harder and stronger Brass (alloy of copper and zinc) is harder than pure copper or pure zinc 2 Improve the appearance of metals Pewter (Alloy of Tin and Antimony) used to make ornaments as it looks more aesthetically pleasing than pure tin 3 Lowering the melting points of metals Solder (Alloy of Tin and Lead) has a lower melting point than most metals. Used for joining circuit boards to electronic parts 4 Increase Corrosion Resistance Cupronickel (Alloy of Copper and nickel) does not corrode easily How are Alloys stronger than constituent Metals? - In an alloy, atoms of the different metals or elements have different sizes,