Structure 2.1

• Ionic compounds consist of ions held together in lattice structures by ionic bonds.
• The solubility and melting points of ionic compounds can be used to explain observations.
• Theory of Knowledge: General rules in chemistry (like the octet rule) often have exceptions.
• Positive ions (cations) form by metals losing valence electrons.
• Negative ions (anions) form by non-metals gaining electrons.
• An ion is a charged particle that forms when atoms gain or lose electrons.
• A cation is a positive ion formed when an atom loses one or more electrons.
• The second edition of Higher Level Chemistry was published in 2014.
• Higher Level Chemistry is a textbook written by Catrin Brown and Mike Ford, published by Pearson Baccalaureate.
• The print version of Higher Level Chemistry has an ISBN of 978 1 447 95975 5.
• The eBook version of Higher Level Chemistry has an ISBN of 978 1 447 95976 2.
• Most of the information found in this power point comes directly from the Higher Level Chemistry textbook by Brown and Ford and is used for direct instructional purposes only.
• An anion is a negative ion formed when an atom gains one or more electrons.
• The charge on an ion is equal to the number of electrons gained or lost.
• The number of electrons lost or gained is determined by the electron configuration of the atom.
• Group 1 elements have one valence electron so they tend to lose one electron and form 1+ ions.
• Group 2 elements have two valence electrons so they tend to lose two electrons and form 2+ ions.
• Group 3 elements have three valence electrons so they tend to lose three electrons and form 3+ ions.
• Group 4 elements do not tend to lose or gain electrons due to the amount of energy involved so they do not normally form ionic bonds.
• Group 15 elements have five valence electrons so they tend to gain 3 electrons and form 3- ions.
• Group 16 elements have six valence electrons so they tend to gain two electrons and form 2- ions.
• Group 17 elements have seven valence electrons so they tend gain one electron to form 1- ions.
• Transition elements have electron configurations that allow them to lose different amounts of electrons from their d-sublevels.
• Transition elements can form more than one stable ion.
• The ions can be distinguished by color.
• Lead forms 4+ and 2+.
• Copper forms 2+ and 1+.
• Tin forms 4+ and 2+.
• Hydrogen can form the hydride H- as well as H+.
• The ionic bond is due to the electrostatic attraction between oppositely charged ions.
• Polar compounds dissolve in polar solvents, nonpolar compounds dissolve in nonpolar solvents, and "like dissolves like".
• The higher the charge and smaller the ion, the greater the melting point.
• Ionic compounds have very low volatility.
• Ionic character can be predicted by two ways: position on the Periodic Table and electronegativity differences.
• The strength of force between the ions is known as lattice enthalpy and depends upon the size of the ion and the charge on the ion.
• The formula unit is the smallest particle of an ionic compound.
• The ions in ionic compounds surround themselves with ions of the opposite charge, forming three-dimensional crystalline structures known as ionic lattices.
• Differences greater than 1.8 are considered to be ionic.
• The coordination number expresses the number of ions that surround a given ion in the lattice.
• Know these polyatomic ions: NH4+, OH- , NO3- , CN- , HCO3- , CO32- , SO42- , PO43-.