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Learning Chemical FormulasPowerPoint Presentation

Learning Chemical Formulas

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Simple Ionic Compounds

Concept:

Ionic Formulas are formed from positive and negative ions.

Fact 1:

Positive ions are formed by metals that lost electrons.

Examples: Na1+ Mg2+ A3+ P4+

Simple Ionic Compounds

- Fact 2: Negative ions are formed by nonmetals that gained electrons. Examples: Cl1- O2- N3- Si4-

Simple Ionic Compounds

Fact 3:

The overall charge of ionic compounds must equal zero.

Examples : Na1+ Cl1- Ca2+Br1- Al3+O2-

Lesson Two--Polyatomic Ion Formulas

Concept:

Polyatomic ions are groups of atoms that behave as one unit.

Fact 4:

Some ions have more that one atom but their overall charge can be determined.

Examples: (SO4) = S +6 and O -8 = -2

(NO3)= N +5 and O -6 = -1

(NH4) = N -3 and H +4 = +1

Polyatomic Ion Formulas

Fact 5: These group ions, polyatomic ions, are treated like single ions in formulas, but must have parentheses when more than one is used in a formula.

Examples: Ca2+(NO3) 1-2 Ga3+ (SO4) 2-

(NH4) 1+2O2-

Polyatomic Ion Formulas

Fact 6:

The polyatomic ions are named based on the atoms that they contain. Those with oxygen and another nonmetal are often name "____ate" with the root of the other nonmetal in the blank.

Examples: (NO3)1- is nitrate

(SO4)2- is sulfate

(ClO3) 1- is chlorate

Polyatomic Ion Formulas

Fact 7:

Those polyatomic ions with one oxygen less than the "ate" ions are named "----ite" ions.

Examples: (NO2)1- is nitrite

(SO3)2- is sulfite

(ClO2)1- is chlorite

Polyatomic Ion Formulas

Fact 8:

Some polyatomic ions contain a regular polyatomic ion and one or more hydrogen ions. Each hydrogen that is present add one positive charge to the total charge.

Examples: (SO4)2-becomes H(SO4)1-

(SO3)2- becomes H(SO3)-1

(CO3)2- becomes H(CO31-

(PO4)3- becomes H(PO4)2-

Polyatomic Ion Formulas

Fact 9:

These ion groups are named hydrogen ____

or bi ______.

Examples: H(CO3)1- is called hydrogen carbonate or bicarbonate

H(SO4) 1- is called hydrogen sulfate or bisulfate

Lesson Three--Transition Metal Compounds

Concept:

Transition metals have electrons in d orbitals and can donate different numbers of electrons, thus giving them several different positive charges.

Fact 10:

These can be determined from the Roman numeral which is written next to the metal's name.

Example: Cu1+is Copper I

Pb2+is Lead II

Fe3+is Iron III

Sn4+s Tin IV

Transition Metal Compounds

Fact 11:

These transition metals are used in formulas just like other metals, once the charge is determined from the Roman numeral in the name.

Example: Cu1+ Cl1- Pb2+O2-

Fe3+Br1-3Sn4+O2-

Transition Metal Compounds

Fact 12:

A few transition metal ions only have one charge and never change so they can be written without a Roman numeral in their formula name.

Example: Ag1+ Zn2+ Cd2+

Lesson Four--Using Formulas in Problem Solving

Concept: Correctly written chemical formulas hold a large amount of information for the prepared student to find.

Fact 13:

The subscripts tell us the number of atoms of each kind that is present in the compound.

Example: NaCl has one atom of sodium and one atom of chlorine.

H2SO4 has two atoms of hydrogen, one atom of sulfur and four atoms of oxygen

Using Formulas in Problem Solving

Fact 14:

The sum of the atomic masses times the number of atoms of each kind of element is equal to the mass of one mole of the substance.

Examples: Na = 23g/mol and Cl = 35.5g/mol so NaCl has a molar mass of 58.5g/mol

Nitric acid is HNO3so its molar mass is

H = 1 x 1 = 1

N = 14 x 1 = 14

O = 16 x 3 = 48

Total = 63g/mol

Using Formulas in Problem Solving

Fact 15:

From the formula ion charges, also called oxidation numbers, can be determined using simple math processes.

Example:Fe2O3 is iron oxide, but what is the charge of the iron in this formula? It is known that the oxygen's ionic charge is -2 so substitute in that charge and find the iron's ionic charge.

Fe--2O-23 It is clear that the missing charge is +3.

Thus the complete name of this compound is

iron III oxide.

Using Formulas in Problem Solving Notice that the total of the percentages is always equal or very close to 100%.

- Fact 16: The percentage composition of each element in a compound can be determined using only the correct formula and the atomic masses.
- Example: Sodium chloride or NaCl
- Na = 23.0 % Na = 23.0 x 100 = 39.3%Na
- Cl = 35.5 58.5
- 58.5g/mol
- % Cl = 35.5 x 100 = 60.7% Cl
- 58.5

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