Ions. Ions : A charged particle formed when a neutral atom or group of atoms gain or lose one or more electrons. Example Na ïƒ Na + + e - F + e - ïƒ F -. Cations. Mg ïƒ Mg 2+ + 2e - Al ïƒ Al 3+ + 3e - Cation: A positively-charged ion. One or more electrons are lost from a neutral atom
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Ions: A charged particle formed when a neutral atom or group of atoms gain or lose one or more electrons.
Na Na+ + e-
F + e- F-
Mg Mg2+ + 2e-
Al Al3+ + 3e-
Cation: A positively-charged ion. One or more electrons are lost from a neutral atom
I + e- I-
O + 2e- O2-
S + 2e- S2-
Anion: A negatively-charged ion. Electrons are gained by a neutral atom
1. Very high melting points
2. Conduct an electric current when melted or when dissolved in water
Writing Formulas for Ionic Compounds
Give the formulas for the compounds that contain the following pairs of ions:
(a) K and I
(b) Mg and N
(c) Al and O
1. The cation is always named first and the anion second.
2. The cation takes its name from the name of the element.
3. The anion is named by taking the first part of the element name and adding –ide.
Type II Ionic Compounds
FeCl2 and FeCl3
PbO and PbO2
MnS and Mn2S7
Polyatomic Ion: An ion that contains more than one atom. They are charged entities composed of several atoms bound together.
Name or provide the chemical formula for each of the following compounds:
(a) Ca(OH)2 (e) Co(ClO4)2
(b) Sodium phosphate (f) platinum (IV) bicarbonate
(c) KMnO4 (g) Cu(NO2)2
(d) Ammonium dichromate (h) nickel (III) oxalate
(a) calcium carbonate (e) MoO
(b) BaSO4 (f) Iridium (VII) acetate
(c) CsClO4 (g) ZnHPO4
(d) Zirconium bisulfite (h) lithium cyanide
Acids: A substance that yields hydrogen ions (protons, H+) when dissolved in water.
ClO4- ______________ HClO4 _______________
ClO3- ______________ HClO3 _______________
ClO2- ______________ HClO2 _______________
ClO- _______________ HClO ________________
Rules for Naming Type III Binary Compounds
1. The first element in the formula is named first, and the full element name is used.
2. The second element is named as though it were an anion.
3. Prefixes are used to denote the numbers of atoms present.
4. The prefix mono- is never used for naming the first element.
5. Drop the “a” when it is followed by an “o”
Tetraoxide should be tetroxide
Prefixes Used to Indicate Numbers in Chemical Names
Calculate the mass of 30.0 moles of polyvinyl chloride (PVC), C2H3Cl.
A sample of Na2SO4.with a mass of 300.0 grams represents what number of moles of Na2SO4?
Calculate the number of grams of caffeine, C8H10N4O2, in 8.13 x 1023 molecules.
Compute the mass percent of each element in sodium sulfide, Na2S.
Compute the mass percent of each element in nitric acid, HNO3(aq).
Empirical Formula: or the simplest formula; the smallest
whole-number ratio of the atoms present.
Molecular Formula: the actual formula of a compound. It gives
the composition of the molecules that are present.
Empirical FormulaMolecular Formula
Steps for Determining the Empirical Formula of a Compound
1. Obtain the mass of each element present (in grams).
2. Determine the number of moles of each type of atom present.
3. Divide the number of moles of each element by the smallest number of moles to convert the smallest number to 1. If all of the numbers are integers (whole numbers), these are the subscripts in the empirical formula. If one or more of these numbers are not integers, go to step 4.
4. Multiply the numbers derived in step 3 by the smallest integer that will convert all of them to whole numbers. This set of whole numbers represents the subscripts in the empirical formula.
Suppose we weigh out 6.50 grams of Cr. We decide to heat this Cr in the air so that the Cr can react with O to form CrxOy . After the sample cools, we weigh it again and find its mass to be 9.50 grams. How do we find the mass of oxygen?
What is the empirical formula of this compound?
Let’s work on this together.
Nylon-6 consists of 63.68% C, 12.38% N, 9.80% H, and 14.14%O.
Calculate the empirical formula for Nylon-6.
We need to know the empirical formula and molar mass of the molecular compound.
Molecular Formula = (empirical formula)n
where n is a small whole number.
Molecular Formula = n x Empirical Formula
Molar Mass = n x Formula Weight
n = Molar Mass/Formula Weight
A compound shows the following percentage compostion:
71.65% Cl 24.27% C 4.07% H
The molar mass is known to be 98.96 g/mol. Determine the empirical formula and the molecular formula for this compound.
Vitamin C consists of 40.92% C, 4.58% H, and 54.50% O on a mass basis, and has a molar mass of 176.12 g/mol. Determine the molecular formula of the compound.