chem 101 topic 3

Discussion of Molecules, Compounds and Nomenclature. Featured compounds include Caffeine and Ibuprofen.

Molecular Formula:
- Chemical symbols to denote types of atoms present in a molecule.
- Subscripts are used only when more than one atom of a given type exists in the molecule, indicating the number for that element.
Structural Formula:
- Similar to the molecular formula but also illustrates how atoms are connected to one another.

Empirical Formula:
- Represents the simplest whole-number ratio of the number of atoms (or ions) in the compound.
Molecular Formula:
- Shows the actual number of each type of atom in a molecule of the compound.
- Example:
- Benzene: Molecular formula = $C6H6$
- Acetic Acid: Molecular formula = $C2H4O2$ , Empirical formula = $CH$ (or $CH2O$ )

Two General Types: Ionic and Covalent Bonds.
Ionic Bonds:
- Electrons are transferred between atoms, producing oppositely charged ions that attract each other.
- Generally involve metal and nonmetal atoms.
Covalent Bonds:
- Two atoms share some of their electrons, typically between nonmetal atoms.
Chemical Bonds:
- Forces of attraction holding atoms together within compounds.

Ionic Substances:
- Exist as arrays of oppositely charged ions stabilized by ionic bonding, forming a crystalline lattice; no discrete molecular units exist.
- Example: Formula unit or empirical formula, which illustrates the lowest whole-number ratio that balances charges to zero.

Molecular View:
- Distinction between elements and compounds.
- Pure Substances: Homogeneous materials with a constant composition.

Metals:
- Tend to lose electrons (e.g., #e- = maximal last digit of group/column number).
Nonmetals:
- Tend to gain electrons or lose them to achieve a full outer shell with eight electrons (octet rule).

Sequence: Name metal cation first, followed by nonmetal anion.
The name of the nonmetal anion changes ending to -ide.
- Example: NaCl = sodium chloride.

Name metal cation first, followed by nonmetal anion.
The metal's name is followed by a Roman numeral in parentheses denoting its oxidation state.
- Example: FeCl₃ = Iron(III) chloride (since three Cl- ions necessitate a +3 charge on Fe).

Free elements have an oxidation state of zero (e.g., Fe(s), O₂(g)).
For ions, the oxidation state equals the charge divided by the number of atoms.
Specific elements have defined oxidation states:
- Alkali metals always +1.
- Alkaline earth metals: +2.
- Hydrogen: +1 (in combination with nonmetals) or -1 (with metals).
- Oxygen: generally -2, except in peroxides and superoxides.
The sum of oxidation states in molecules or ions equals the overall charge.

The more electropositive element is named first, using its full name.
The second element’s name ends with -ide; use prefixes to indicate numbers (except mono on the first element).
Example of prefixes: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca.

Definition: Ions made up of covalently bonded atoms carrying an overall charge.
Example: Carbonate ion $CO3^{2-}$ in Calcium carbonate, $CaCO3$ .

Acids are characterized by containing H+ ions when dissolved in water; labeled as (aq).
Distinction between Binary Acids (hydrides of nonmetals) and Oxyacids (acids with oxygen).

Start with the prefix "hydro" followed by the nonmetal's name.
Change the nonmetal's ending to “-ic”, then add the word "acid".
- For instance, $HCl$ becomes hydrochloric acid.

Types: Based on the number of oxygens and hydrogens.
Example of oxyacids includes HNO₃ (Nitric acid) and HNO₂ (Nitrous acid).
- The naming is based on whether the corresponding oxyanion ends in -ate (to -ic) or -ite (to -ous).

Three classes of organic compounds: Hydrocarbons, Compounds containing O, and Compounds containing N.
Organics utilize a systematic naming convention developed by IUPAC focusing on substituents, carbon numbers in the main chain, and the principle functional group.

Hydrocarbons:
- Alkanes: Only single bonds (saturated).
- Alkenes: At least one C=C double bond.
- Alkynes: At least one C≡C triple bond.
- Aromatic: Alternating single and double bonds in rings.

Carbon Atoms:
- 1: met
- 2: eth
- 3: prop
- 4: but
- 5: pent
- 6: hex
- 7: hept
- 8: oct
- 9: non
- 10: dec

Alcohols:
- Contain hydroxyl (-OH) functional group.
- Nomenclature involves naming the longest carbon chain, ending with -ol.
Aldehydes:
- Contain carbonyl group (C=O) with a general structure of $RCHO$ ; named as -al.
Carboxylic Acids:
- Feature carboxyl (COOH) and are named as -oic acid.

Understanding the percent composition helps to derive molecular and empirical formulas.
Utilize combustion analysis to ascertain atomic makeup by burning a sample in oxygen.

Formulas and names for various ionic and molecular compounds discussed in earlier sections. Tasks include formula writing and identifying structures and functional groups.
Include practical exercises for naming and drawing organic structures based on functional groups and molecular arrangements.

Clear understanding of chemical formulas, nomenclature, bonding types, and organic compounds is essential for mastery in chemistry. Regular practice through naming, writing formulas, and visualizing structures will reinforce learning and application in various chemical contexts.