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)