names and formulas of compounds. ion an atom or bonded group of atoms that have lost or gained...
TRANSCRIPT
Names and Formulas of
Compounds
ion
• An atom or bonded group of atoms that have lost or gained electrons to become charged
• Lose electrons= + charge• Gain electrons= - charge• The number of electrons lost/gained
determines the charge on the ion
Monatomic ion
• A one atom ion
Oxidation number
• The charge on a monatomic ion
Valence electrons
• The outermost electrons that are involved in chemical bonding
• Group number will tell how many valence electrons, disregarding any ones in the ten’s place
• Ex: Group 1 has 1 valence e- Group 13 has three valence e- Group 18 has 8 valence e-
Octet Rule
• All atoms- except for hydrogen and helium- need 8 electrons in their outmost energy level to be stable– Hydrogen and helium need 2 electrons
to be stable• Atoms bond with each other to
become stable• Bonds can be ionic or covalent
Formation of ions
• Elements in groups 1-13 form positive ions– Most of the transition metals can form
ions with multiple charges– Example: copper can form +1 and +2
ions• Elements in group 14 can be +4 or -4• Elements in groups 15-17 tend to
form negative ions
Ionic Bond• Forms when electrons are transferred
form atom to another, creating ions• Ions of opposite charge are attracted to
each other and an ionic compound is formed
• The sum of the charges of the ions in an ionic compound must equal ZERO– For a compound formed from Cu 2+ and
F- , two fluorine ions are needed to balance the copper ion charge
– Ex: (2+) + (1-) + (1-) = 0
Ionic compound
• Compound formed by the electrostatic attraction between ions of opposite charge
• Ex: Na+ and Cl -
Formula unit
• Simplest ratio of the ions in an ionic compound
• CuO not Cu2O2
Binary compounds
• Made up of two ELEMENTS, not atoms
Cation and anion• Cation- positive ion, usually a metal
– Written first in the name and the formula– Is the element name– Roman numeral in parentheses gives the
charge for elements that have more than one possible charge
• Anion- negative ion, a nonmetal or metalloid– Written last in the name and formula– Drop element ending and add suffix –ide– Ex: oxygen=oxide, chlorine=chloride
Writing formulas for binary ionic compounds
• Determine the charge on the cation• Determine the charge on the anion• Criss cross the numbers, NOT the + and -• Write the formula:
– Cation symbol first with subscripts to show how many are in the formula
– Anion symbol last with subscripts to show how many are in the formula
– Simplify if needed to get smallest whole number ratio
Practice
• Write formulas for:• The compound formed from
magnesium and fluorine• compound formed from aluminum
and oxygen
Writing formulas from names• The name will tell you which
elements are involved• Follow the same rules already given• EX: magnesium sulfide• EX: sodium hydride
Practice
• Write formulas for each of the following ionic compounds:
1. Sodium fluoride
2. Aluminum chloride
3. Barium sulfide
Ions with multiple charges
• Some elements can form ions with different charges
• Example: copper can have +1 or +2 charge
• This affects the chemical formula and the properties of the compound formed
• Must indicate which charge is present for that ion
Ions with multiple charges
• Stock system– Uses parentheses and Roman
numerals to indicate charge– EX: copper (I) has a 1+ charge
Writing formulas with Stock system• The Stock system tells you the
CHARGE of the cation inside parentheses, NOT the number of ions
• EX: copper (I) bromide• Cu1+ Br1-
• CuBr
Polyatomic ions
• Ions that contain more than one element
Writing formulas with polyatomic ions
• The same general rules apply as with binary compounds
• Determine ion charges• Determine how many of each ion are needed
to equal zero• Write cation symbol and anion symbol • Place subscripts for each ion in the formula
– If only one polyatomic ion is needed, no subscript– If more than one polyatomic ion is needed, place the entire
polyatomic ion symbol in parentheses, then write subscript outside the parenthesis
Practice
• Write formulas for :
1. Potassium hydroxide
2. Calcium nitrate
3. Ammonium chlorate
Multiple charges and polyatomic ions• Formulas for compounds with a cation
with multiple charges and a polyatomic ion are written just like any other compound formula
• Determine charges on ions• Write cation and anion symbols with
charges• Criss cross numbers• Place polyatomic ion in parentheses if you
have more than one in the compound’s formula
Practice
• Write the formula for each of the following compounds:
1. Copper (II) sulfate
2. Manganese (III) nitrate
3. Iron (II) phosphate
4. Iron (III) dichromate
Naming ionic compounds• Binary compounds:
– Name cation first with the element name
– Name anion last. Drop the element name ending and add the suffix -ide
• Non-binary compounds:– Name cation first, element or
polyatomic ion name– Name anion last, polyatomic ion keeps
its name, monatomic ion ends in -ide
Practice
• Name the following compounds:
1. CaS
2. Na3N
3. Mg(NO2)2
4. (NH4)2SO4
Naming with the Stock system• Names of cations with more than one
charge MUST indicate which charge is on the ion by placing a Roman numeral in parentheses after the cation
• This Roman numeral indicates CHARGE not number of ions
• Example: CoCl2 is cobalt (II) chloride
Practice
• Name the following using the Stock system:– Cu2S
– CuS– Fe(NO3)2
– Fe(NO3)3