Structure and Bonding

Not soluble in Non Polar Solvents eg-cyclohexane.

*IONIC Substances* do not dissolve because ionic bonding is too strong to be overcome by the solvent which has no charges. *METALLIC Substances* do not dissolve because metallic bonding is too strong to be overcome by the solvent which has no charges. *Covalent Molecular (POLAR)* substances do not dissolve because the attractions between the polar molecules with the partial charges are too strong to be overcome by the solvent which has no charges. *COVALENT NETWORK Substances* do not dissolve because the strong covalent bonds throughout are too strong to be overcome by the solvent which has no charges.

Non Polar Covalent Bonds

-A non-polar covalent bond forms when a shared electron pair is attracted to the nuclei of both atoms EQUALLY. -Formed betwen non-metal atoms that have the SAME ELECTRONEGATIVITY.

Polar covalent bonds

-A polar covalent bond is formed when electrons are shared UNEQUALLY between atoms. -The shared electrons are attracted to (so found closer to) one atom more than the other.. -Polar covalent bonds are formed between non-metals atoms with DIFFERENT ELECTRONEGATIVITIES. -Electrons found closer to the more electronegative atom will have a slightly negative charge (S-) -The less elctronegative atom will have a slightly positive charge (S+)

What are the 5 atoms that don't require 8 electrons to have a full valance shell?

-H, He and Li only require 2 valance electrons. -Be (Beryllium) only requires 4. -B (Boron) only requires 6.

Solubility in Polar Solvents eg-water

-Some ionic substances dissolve (eg Na+, K+, Cl salts) Because there is a strong attraction between the charges on the ions and the partial charges on the water *("Like dissolves like")* -Covalent Molecular (POLAR) dissolve in polar substances because there is an attraction between the partial charges on the polar molecules and the partial charges on the water. *("Like dissolves like")*

Electronegativity

-This describes how strongly the bonding electrons are attracted to the nucleus of an atom. -Elements on the RHS of the periodic table are the most electronegative.

Covalent Bonding

-This is when electrons are SHARED between two atoms.(equal sharing) -The bonding electrons 'belong' to both atoms at the same time. -Covalent bonds form between the atoms of NON-METALS.

Ionic Bonding

-This is when electrons are TRANSFERRED between atoms. (extreme case of unequal sharing) -Electrically charged particles called IONS are formed. -The force of attraction between positive (cations) and negative ions (anions) is called an ionic bond.

Lewis Structure (electron dot diagrams)

-Used to represent the arrangement of electrons in species that contain covalent bonds. -Only shows the valence electrons. -The shared electrons are called BONDING electrons. -Electrons not involved in bonding are called NON-BONDING electrons or LONE PAIRS of electrons.

Writing frame for explaining Polarity of Molecules

1.Substance name or formula 2.Number and type of bonds. 3.Bonds are polar due to the differing electronegativities of the atoms. OR Bonds are non polar due to the same electronegativities of the atoms. 4.The molecule has a balanced/unbalanced shape (shape name) 5.So the effect of the polar bonds is cancelled/not cancelled. 6.Therefore the whole molecule is polar/non polar overall.

Writing frame for explaining Shape/Bond Angle

1.Substance name or formula 2.Number of electron clouds around the central --- atom. 3.Number of Bonding pairs and non bonding pairs. 4.All of these repel each other as far apart as possible. 5.Pushing the bonds into a -------------- shape. 6.Giving a bond angle of ---------.

Writing frame for explaining Properties of substances in terms of their Structure and Bonding.

1.Substance name or formula 2.Type of substance 3.Describe structure (Name) is composed of a three dimensional lattice of.. 4.Describe bonding (Name's) lattice is held together by...... 5.Explain why the property exists

Writing frame for explaining Solubility/Dissolving

1.Substance one-type of substance 2Substance two-type of substance 3.Strength of attraction between substances 4.compare with attractions within substance 5.(support your answer with a diagram)

Shapes of Molecules (four electron clouds)

Bond angle: 109 Shape:(No lone pairs) Tetrahedral Shape: (One lone pair) Trigonal Pyramidal Shape:(Two lone pairs) Vshaped/Bent Shape: (Three lone pairs) Linear

Shapes of Molecules (three electron clouds)

Bond angle: 120 Shape: (No lone pairs) Trigonal Planar Shape: (One lone pair) Vshaped/Bent

Shapes of Molecules (two electron clouds)

Bond angle: 180 Shape: Linear o-------0-------o

Covalent Network Solid *examples*

Carbon(diamond,graphite) Si, SiO2 and SiC Memorise these five!

Solubility in Non Polar Solvents eg-cyclohexane.

Covalent Molecular (NON POLAR) dissolves because the non polar substance and the non polar solvent can spread within each other since both have weak intermolecular forces. *("Like dissolves like")*

Covalent Molecular Solids

Covalent molecular solids consist of a 3D lattice of WHOLE MOLECULES. The lattice is held together by WEAK INTERMOLECULAR FORCES. -Low melting point, showing the intermolecular forces are weak. -Do not conduct electricity as there are not charged particles present that are free to move.

Covalent Network Solids

Covalent network solids consist of a 3D lattice of ATOMS. The lattice is held together by COVALENT BONDS. -Very high melting point meaning covalent bonds are very strong. -Do not conduct as there are no charged particles present that are free to move. *exception: Graphite*

Covalent Molecular Solid *examples*

EG H2O, CO2, CH4, H2, 02, He, Ne, Cl2, Br2.... It is a non metal and a non metal

Metallic Solid *examples*

EG Na, Mg, Zn, Fe.... It is one word/from the left or middle of periodic table.

Ionic Solid *examples*

EG NaCl, KI, CuSO4, NH4Cl... It is a metal and a non metal OR ammonium and a non metal.

Ionic Solids

Ionic solids consist of a 3D lattice of alternating positive and negative ions. The lattice is held together by IONIC BONDS, which are the ELECTROSTATIC ATTRACTION between the positive and negative charges of the ions. -Have high melting points, meaning ionic bonds are strong. -Conduct electricity if it is molten or dissolved as there are charged particles present that are free to move. If it is solid it will not conduct.

Not soluble in Polar Solvents eg-water

METALLIC because metallic bonding is too strong to be overcome by the partial charges of water. Covalent Molecular (NON POLAR) because there is no attraction between the non polar molecules and the partial charges on the water. COVALENT NETWORK, Because the strong covalent bonds throughout the network are too strong to be overcome by the partial charges of the water.

Metallic Solids

Metallic solids consist of a 3D lattice of metal atoms in a sea of delocalised valance electrons. The latice is held together by METALLIC BONDS, which are the ELECTROSTATIC ATTRACTION between the nuclei of the atom(positive) and the delocalised electrons(negative) -High melting point so metallic bonds are strong. -Conduct electricity as there are charged paticles present that are free to move.

6 Steps to a Lewis Structure

Step 1: Draw atoms symmetrically around the central atom. Step 2: Count up the total number of valence electrons. Step 3: Place two electrons (one covalent bond) between each pair of atoms. Step 4: Place any remaining electrons around the outside atoms so that the valence shell of each atom is full. (with 8 electrons) Step 5:Place any remaining electrons on the central atom as lone pairs. Step 6: If any atom has an incomplete valance shell, move electron pairs to create multiple bonds.

Charge Separation

This is called a DIPOLE -A polar bond has a bond dipole or dipole moment.