Chemical Names and Formulas Ch. 6

Introduction to Chemical Bonding 6-1

Molecules Molecule = two or more nonmetal atoms that act as a unit –Ex: O 2, CO, H 2 O Diatomic Molecules = elements whose natural state has two identical elements –Ex: H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

Molecular Compounds Molecular Compound = compound composed of molecules Most composed of 2 or more nonmetals Low melting + boiling points Most gases or room temp. Ex: H 2 O, CO 2, CH 4, NH 3

Ions Ions = atoms or groups of atoms that are charged. Forms when atom or group of atoms loses or gains electrons. –Throws off neutral atom of p + = e - creating a charge

Cation + Anion Cation = atom or group of atoms that has a positive charge. –All metals are cations –Cations lose electrons, becoming positive –Cation name stays the same as element name –Ex: Na + (sodium), Mg +2 (magnesium), Al +3 (aluminum) Anion = atom or group of atoms that has a negative charge. –All nonmetals are anions –Anions gain electrons, becoming negative –Anion name ends in -ide –Ex: Cl - (chloride), O -2 (oxide), N -3 (nitride)

Ionic Compound Ionic Compound = compound composed of cations and anions. –Metal cation + nonmetal anion –Are electrically neutral, positive cation balances out negative anion. –Write the metal first and the nonmetal second. –Ex: NaCl, CaO

NaCl: –Na loses 1 electron, becoming Na + (cation) –Cl gains 1 electron, becomes Cl - (anion)

Properties of Ionic Compounds Ionic compounds have different properties from the properties of elements that make it up. –Solid room temp. –High melting point Ex: table salt (NaCl) = chlorine (Cl) + sodium (Na) –Chlorine by itself is a fatal green gas –Sodium by itself is explosive when in it comes into contact with water! –Together they make edible table salt!! + =

Comparing Molecular + Ionic Compounds Molecular Compound: –Neutral molecule –2 or more nonmetals together –Usually liquid or gas –Low melting point Ionic Compound: –Made up of 2 or more charged ions –Neutral compound –Metal + nonmetal –Solid crystal –High melting point

DRAW! Molecular

Representing Chemical Compounds 6-2

Formulas Molecular Formula = represents molecular compounds –Ex: H 2 O, CO 2, C 6 H 12 O 6 Formula Units = represents ionic compounds –Lowest whole # ratio –Ex: NaCl, MgCl 2, AlCl 3

Ionic Charges 6-3

Monatomic Ions Monatomic Ions = ions consisting of only one atom. Charges can be determined using the periodic table! –Group 1: charge is +1 –Group 2: charge +2 –Group 13: charge +3 –Group 14: none – don’t make ions –Group 15: charge -3 –Group 16: charge -2 –Group 17: charge -1 –Group 18: none – don’t make ions

DRAW! Charge:

Transition Element Charges Many transition elements (groups 3-12) have more than one possible charge. –Use roman numerals to differentiate between them –Iron (Fe): Fe +2 is Iron (II) Fe +3 is Iron (III) –Copper (Cu):Cu + is Copper (I) Cu +2 is Copper (II) Some transition elements have only one charge. –Ex: Ag +, Cd +2, Zn +2 See Page 144!

Polyatomic Ions Polyatomic Ions = tightly bound group of atoms that behave as a unit and carry a charge. –Ex: SO 4 -2, NO 2 -, CO 3 - –For naming pairs of polyatomic ions, name according to # of oxygen atoms: Suffix –ite has one less oxygen then –ate Ex: SO 3 -2 sulfiteSO 4 -2 sulfate NO 2 - nitriteNO 3 - nitrate ClO 2 - chloriteClO 3 - chlorate

Polyatomics Memorize (for 10/22) Ammonium NH 4 + CyanideCN - NitrateNO 3 - SulfateSO 4 -2 PhosphatePO 4 -3 HydroxideOH - Zinc*Zn +2 ChlorateClO 3 - Silver*Ag + Acetate C 2 H 3 O 2 - CarbonateCO 3 -2 Assumed to Know (for 10/30) NitriteNO 2 - SulfiteSO 3 -2 PhosphitePO 3 -3 Transition metal ChloriteClO 2 - Transition metal CarboniteCO 2 -2 See page 147

Ionic Compounds 6-4

Writing Formulas for Binary Ionic Compounds Binary compound = compound composed of 2 elements. –Must be a neutral compound - positive charge must balance the negative! –Ex: Na + + Cl - = NaCl = 0 –Ex: Ca +2 + F - = CaF (-1) = 0 Confusing?… just cross the charge to become a subscript! Ca +2 + F - CaF 2

More Examples Ex: K + I = ? –What are the charges? –K +1 and I -1 – = 0 –KI Ex: Li + O = ? –What are the charges? –Li +1 and O -2 HINT: cross the charges! –Li +1 and O -2 – Li 2 O

You Try! Write the formula: 1.Ca + O Ca +2 + O = 0 …CaO 2.Na + S Na +1 + S -2 Na 2 S 3. Al + O Al +3 + O -2 Al 2 O 3 4. B + N B +3 + N =0 …BN

Naming Binary Ionic Compounds Write the cation first (+) then anion (-), OR metal first then nonmetal. Remember: only anion name changes to suffix –ide! Ex: Na + + Cl - = NaCl sodium + chlorine = sodium chloride! Al +3 + F - = AlF 3 aluminum + fluorine = aluminum fluoride!

You Try! Write the formula and name it: –Li + N Li + + N -3 Li 3 N Lithium nitride –Mg + Cl Mg +2 + Cl - MgCl 2 Magnesium chloride B + O –B +3 + O -2 –B2O3–B2O3 –Boron oxide K + I –K + + I - –KI –Potassium iodide

If transition metals are involved, you need to know which charge is used… –Ex: CoI 2 (cobalt could be +2 or +3) Co ? + I - CoI 2 Cobalt must be Co +2, so the name is… Cobalt (II) iodide!

Tertiary Ionic Compounds Tertiary Ionic Compounds = compound with 3 different elements. –Usually contain 1 or more polyatomic ions –Ex:calcium + nitrate Ca +2 + NO 3 - Ca(NO 3 ) 2 Use parentheses if more than 1 of polyatomic!

More Examples Lithium carbonate Li + + CO 3 -2 Li 2 CO 3 Potassium sulfate K + + SO 4 -2 K 2 SO 4 Ammonium sulfite NH SO 3 -2 (NH 4 ) 2 SO 3 Chromium (III) nitrite Cr +3 + NO 2 - Cr(NO 2 ) 3

Molecular Compounds and Acids 6-5

Binary Molecular Compounds Binary Molecular Compounds = 2 nonmetals. No charges to balance! When naming, prefixes are used for both elements. No mono- on first element! The second element has the suffix –ide Write the element that is most left in the table, or if in the same group closest to the bottom, FIRST Ex: N 2 O – dinitrogen monoxide PCl 3 – phosphorus trichloride

# of AtomsPrefix 1Mono- 2Di- 3Tri- 4Tetra- 5Penta- 6Hexa- 7Hepta- 8Octa- 9Nona- 10Deca-

You Try! Write the name: –OF 2 Oxygen difluoride –N2O5–N2O5 Dinitrogen pentoxide –Cl 2 O 8 Dichlorine octoxide Write the compound: –Nitrogen trifluoride NF 3 –Disulfur dichloride S 2 Cl 2 –Sulfur hexafluoride SF 6

Naming Common Acids An acid is a hydrogen ion (H + ) and an anion Common one’s to know: –Hydrochloric AcidHCl –Sulfuric AcidH 2 SO 4 –Nitric AcidHNO 3 –Acetic AcidHC 2 H 3 O 2 –Phosphoric AcidH 3 PO 4 –Carbonic AcidH 2 CO 3