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 CHARGESNeed to balance the charges

i.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)