NAMING IONIC COMPOUNDS
Sec. 2.2 Part AScience 10
REVIEW
How do atoms form ions? Why do they want to form ions? What are positively charged ions
called? Negatively charged ions? What can occur once ions have been
created? Why does this occur?
OBJECTIVES
explain why the IUPAC system of naming compounds is important
describe the process of ionic bonding and give examples of ionic compounds
give correct names and formulas for ionic compounds, using the periodic table, table of ions and IUPAC rules
IUPAC AND COMPOUND NAMING
IUPAC – International Union of Pure and Applied Chemistry
Responsible for naming compounds Allows consistent way of naming
compounds Why is this important?
Allows for clear and precise communication
IONIC COMPOUNDS
How do we form ionic compounds? Transfer of electrons between atoms Metal and non-metal
Transfer of electrons creates full outer energy levels More stable Attraction of ions called ionic bonding
IONIC COMPOUNDS
Practice: Give drawings and show electron transfer for the following atoms: Sodium Magnesium Chlorine Oxygen
NAMING IONIC COMPOUNDS: THE RULES Two part name: cation and anion 1) name cation first with element’s
name 2) name anion second with first part of
name and change last part to “ide” Ex. Sodium chloride (sodium ion and
chloride ion) IMPORTANT: always write names of
elements as lower case (unless at beginning of sentence)
PRACTICE
Name the following compounds: MgO BaF2(s) K3N(s)
FORMULAS FOR IONIC COMPOUNDS
Contains element symbols Some have subscripts
Ex. BaF2(s)
What this means: One barium ion for every two fluoride ions
Ionic compounds are neutral Therefore, need to have enough of each
atom to cancel the charges out
FORMULAS FOR IONIC COMPOUNDS
What are the charges for each ion in this compound? Sodium chloride
How many of each ion do we need to cancel the charges out?
How about this one? Magnesium chloride How many do we need? These make the subscripts!
STEPS FOR WRITING FORMULASSteps Example Example
Sodium chloride
Aluminium chloride
Identify ions and charges sodium: Na+chloride: Cl-
Determine total charges needed to balance
Na+ : 1Cl- : 1
Note the ratio of cations to anions
1 to 1
Use subscripts to write formula
NaClIf the ratio is 1:1, do not need to include subscriptsThe subscripts should be the simplest form
What does this mean?Formula unit- name for ionic compound unit (NEUTRAL)
aluminium: Al3+
chloride: Cl-Al3+ : 3Cl- : 1+1+1=31 to 3
AlCl3
LOWEST COMMON MULTIPLE
When charges are not easy to balance: i.e. calcium nitride Ca2+ and N3-
Find the lowest common multiple to balance the charges
What is the lowest common multiple here? Simplify!!! What do you end up with?
BALANCING CHARGES
Need to balance the chargesi.e. one positive charge balances out one negative charge
Why do we need to balance the charges? What happens to our compounds when we do this?
PRACTICE
Write the formulas/names for the following compounds: sodium bromide calcium nitride magnesium oxide aluminium chloride MgS AlN Li3P
MULTIVALENT ELEMENTS
Some metals have more than one stable ion Ex. Iron has two stable ions: Fe2+ and Fe3+.
To indicate which ion it is, use Roman numerals in names Example: iron (II) or iron (III)
Still use subscripts for compounds- be careful about which ion it is! Ex. FeBr2 = iron (II) bromide Ex. FeBr3
Only use Roman numerals when more than one ion (ONLY for transition metals)
PRACTICE
Write formulas for following: copper (I) nitride lead (IV) chloride nickel (III) oxide
Write the names for the following formulas: AuN CrO TiBr4
NAMING IONIC AND MOLECULAR COMPOUNDS
Sec A2.2 Part BScience 10
REVIEW
How does an ionic compound form? What name would you give for the
following? MgCl2 LiBr K3N FeCl3
OBJECTIVES
predict formulas and write names for ionic compounds with polyatomic ions
describe covalent bonding in molecular compounds
identify diatomic/polyatomic molecular elements
give correct names and formulas for molecular compounds with and without hydrogen using periodic table and IUPAC rules
POLYATOMIC IONS
Polyatomic ions- ions made of several non-metallic atoms
Come as one “unit” (consider to be one unit when naming)
List in periodic table of polyatomic ions with symbol and charge
Ending usually “-ate” (more oxygen) or “-ite” (less oxygen)
NAMING WITH POLYATOMIC IONS
Cation + anion DO NOT change the ending of a
polyatomic ion Practice: Au(NO3)3(s)
(NH4)3PO4(s)
K2Cr2O7(s)
WRITING FORMULAS
Same method with exception: Subscripts for polyatomic ions placed in
brackets Ex. Fe2(SO4)3
Put 3 outside brackets because there are 3 SO42- for
each Fe3+
Practice: barium hydroxide iron (III) carbonate copper (I) permanganate
MOLECULAR COMPOUNDS
Molecule: two or more non-metal atoms bonding
Can be same or different atoms Fixed numbers of bonded atoms (unlike
ionic compounds: formula unit= part of crystal lattice)
COVALENT BONDS
How molecular compounds bond Atoms share electrons (no transfer) Pair of shared electrons makes one
covalent bond Allows outer energy levels to be filled Can share more than one pair of
electrons (double or triple bonds) http://www.youtube.com/watch?
v=QqjcCvzWwww
MOLECULAR ELEMENTS
Elements that form own molecules (ex. O2)
Diatomic- molecule made of 2 of the same atom H2, N2, O2, F2, Cl2, Br2, I2.
Polyatomic- More than two of the same atom O3, P4, S8.
Only appear as these when by themselves
Should memorize these!
NAMING MOLECULAR COMPOUNDS WITHOUT HYDROGEN
For binary compounds (two elements) Use Greek prefixes:
What are they for numbers 1-10? Indicates how many of each atom
Prefix + first element followed by prefix + second element ending in “-ide”
Ex. N2O (dinitrogen monoxide) PBr3
CO CS2
PRACTICE
Write the names or formulas for the following:
CO2(g)
N2O(g)
PCl3(g)
oxygen difluoride dinitrogen tetrasulfide sulfur trioxide
NAMING MOLECULAR COMPOUNDS WITH HYDROGEN
Often given names Ex. “water” official IUPAC name for H2O Table A2.12 (Be familiar with this chart!
Should know the important ones/ones you will see most often)
HOW DO WE TELL THE DIFFERENCE?
Go through difference between ionic and molecular compounds How do we know which is which and when
to use what naming rules (dichotomous key)