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Chemical Names and Formulas

Chemical Names and Formulas. The naming of the compounds depends on the type compound: Molecular compounds Ionic compounds Binary ionic compound Containing a transition metal Containing a polyatomic ion Acids Binary acids Oxy Acids. Chemical Names and Formulas.

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Chemical Names and Formulas

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  1. Chemical Names and Formulas • The naming of the compounds depends on the type compound: • Molecular compounds • Ionic compounds • Binary ionic compound • Containing a transition metal • Containing a polyatomic ion • Acids • Binary acids • Oxy Acids

  2. Chemical Names and Formulas • In naming molecular compounds • Prefixes are used to indicate the number of atoms in each molecule • It would be impossible to determine the formula without the prefixes

  3. Chemical Names and Formulas • The naming system is straightforward except… • We never begin a formula name with mono • CS2 – Carbon disulfide • We eliminate the –a or –o in the prefix if the element begins with a or o • N2O5 – dinitrogen pentoxide • We change the second element’s ending to -ide

  4. Chemical Names and Formulas • Ionic compounds are compounds made up of ions of opposite charges • A chemical formula is the lowest whole number ratio of the ions present in the compound Na2Cl2 can be reduced to NaCl • The ratio of the ions will depend on the charge of those ions

  5. Chemical Names and Formulas • The charge is sometimes referred to as the oxidation number or oxidation state • Ions formed from one atom are called monoatomic ions

  6. Chemical Names and Formulas • Binary ionic compounds are made up of only 2 different elements • There can be more than 2 or more atoms though • NaCl • K2O • Al2S3

  7. Chemical Names and Formulas • To name a binary ionic compound • Write the name of the cation first (always a metal) • Write the name of the anion, but change the ending to –ide • Note that any subscripts do not change the name NaCl sodium chlorine → chloride sodium chloride

  8. Chemical Names and Formulas K2O Al2S3

  9. Chemical Names and Formulas • Name the following compounds • KI • MgO • SrS • BeF2 • Li2O • Al2O3 • Cs3N • Ba3P2

  10. Chemical Names and Formulas • To write formulas it is important to remember that the charges on the compound must be balanced • Same total number of positive and negative charges • Determine if the charges are balanced • Sodium chloride • Lithium oxide • Potassium iodide • Beryllium bromide • Sodium nitride

  11. Chemical Names and Formulas • When charges are not balanced, it is necessary to add subscripts • They represent the quantity of each element • No subscript equals 1 atom • Li+ O2- the charges are not equal • There is only one positive and two negatives • We need another positive charge to make them equal • Li2O

  12. Chemical Names and Formulas • Write formulas for the following compounds • Sodium sulfide • Potassium iodide • Calcium bromide • Aluminum oxide • Boron bromide • Rubidium selenide

  13. Chemical Names and Formulas • Sometimes the metal in a compound is a transition metal • Groups 3-12 contain the transition metals • Transition metals can move their electrons from the s to the d orbitals • This gives them various oxidation numbers or charges • For example iron can be either Fe2+ or Fe3+

  14. Chemical Names and Formulas • Since these metals do not have a set charge, we must indicate their charge in the name, using Roman numerals • For example look at the three possible compounds that chromium can form with oxygen • Cr2+ and O2- yields CrO called chromium (II) oxide • Cr3+ and O2- yields Cr2O3 called chromium (III) oxide • Cr6+ and O2- yields CrO3 called chromium (VI) oxide

  15. Chemical Names and Formulas • When writing a formula for a transition metal compound remember that the charge of the metal is in the parentheses • Write formulas for the following: • Lead (IV) chloride • Iron (III) oxide • Titanium (II) nitride • Niobium (V) bromide • Tin (II) oxide

  16. Chemical Names and Formulas • Almost all metals get a roman numeral to show the charge • The following do NOT use a roman numeral • Group 1 metals • Group 2 metals • Al3+ • Zn2+ • Ag1+

  17. Chemical Names and Formulas • To write formulas for compounds containing transition metals, we must work backwards: • You will always start with a balanced formula: FeO CoCl2 Au3N

  18. Chemical Names and Formulas • Polyatomic ions are ions that contain more than one atom • SO42- • OH- • PO43- • NH4+ • It is important to note that the charge is distributed throughout all the atoms in the ion • Not only on the last atom!

  19. Chemical Names and Formulas • To name a formula containing a polyatomic ion we must first identify it • If the ionic compound formula contains more than two elements, you have a polyatomic ion present • We do not change the endings of any polyatomic ion

  20. Chemical Names and Formulas • For example, NaOH is • Na2SO4 is • Ca(OH)2is We do not include the subscript outside of the parentheses when naming the compound

  21. Chemical Names and Formulas • To write formulas of ionic compounds containing polyatomic ions: • Calcium carbonate - • Charges are balanced so • Calcium hydroxide - • Charges are not balanced - we need an additional OH-,but we must use parentheses – • Sodium carbonate – • Charges are not balanced – we need an additional Na+, but we do not need parentheses – • Parentheses are only needed when you add a subscript to a polyatomic ion

  22. Chemical Names and Formulas • Bases (ending in OH-) are named as taught before • A common base with a different name is NH3 –ammonia • Acids have a completely different naming system • There are two types of acids • Binary acid – contains H+ and anion(-) • Oxy (Ternary) acid - contains H+ and polyatomic ion(-)

  23. Chemical Names and Formulas • To name a binary acid • Use a prefix hydro • Add the anion name with an –ic ending • Finish with acid • HCl becomes hydrochloric acid • HBr becomes hydrobromic acid • H2S becomes hydrosulfuric acid

  24. Chemical Names and Formulas • To write a formula for a binary acid • Identify that it’s a binary acid – must start with hydro • Write the H+ and the other element with the charge • Balance the charges • Hydronitric acid becomes • H+ N3- • H3N

  25. Chemical Names and Formulas • To name an oxy (ternary) acid • Start with the polyatomic name • If the polyatomic ends in -ate, change the ending to –ic • If the polyatomic ends in –ite, change the ending to –ous • Finish with acid • H2SO4 becomes sulfuric acid • H2SO3 becomes sulfurous acid

  26. Chemical Names and Formulas • To write a formula for an oxy (ternary) acid • Identify that it’s an oxy acid (no hydro in name) • Start with H+ • Add name of polyatomic • Remember that -ic means it ends in -ate and -ous means it ends in -ite • Balance the charges • Nitric acid becomes • H+ NO3- • HNO3

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