| Ionic and Molecular Compounds
IONIC COMPOUNDS are metal-nonmetal combinations [ex: NaCl] The simplest of ionic compounds are binary compounds, which are created from two monatomic ions. [Ex: Na+ and Cl- have positive/negative charges of +/- 1] Note: Cations are positively charged ions (Cat Paws; �Paws� = pos.; positive) and Anions are negatively charged ions. Therefore, the cation Na+ and the anion Cl- combine to create a stable compound with no charge giving us NaCl(s). However, some ionic compounds are not binary. [Ex: AlCl3(s) is made from the Cation Al3+ and the anion Cl-] In order to create a balanced, neutral compound, there must be three Cl-�s for every one Al3+ Therefore: Al3+ + 3Cl- => AlCl3 The subscript numbers show how many atoms of a substance are present within each compound. The substances listed above have a Net Charge of zero; however, some substances have a positive or a negative Net Charge. [NO3-, Co32-, SO42-, ClO3-] The superscript numbers show the net charge of the compound. POLYATOMIC IONS are compounds made of a group of ions with a net positive or negative charge low made with compounds such as those above. [ex: NaNO3 => Na+( NO3-,) ? net charge = 0 K2CO3 => K2+( Co32-) ? net charge = 0] When writing Ionic compound formulas, there is one simple trick to remember: Change Houses, Go Downstairs [ex: Let�s say that you want to write a compound formula for the ombination of aluminum and oxygen 1) Start by writing out the elements with their charges. Al3+ + O2- => Al2O3 2) Ignore negative signs, the numbers will be positive 3) Then the charges �change houses� (the 2 moved to Al and the 3 moved to the O) and then �go downstairs� (becoming subscripts).] When naming Ionic Compounds, there are some basic rules to follow: 1) The metal element always is listed first 2) The nonmetal element�s ending is changed to an �-ide� [ex Aluminum Chloride, Sodium Oxide, Iron Sulfide] |
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