Chem161, unit4

Ionic vs Covalent Bonds

Ionic: Metal + Non-metal

Covalent: Non-metal + Non-metal

How is an empirical formula different from a molecular formula?

The molecular formula shows the actual number of each atom in a molecule, while the empirical formula shows the simplest ratio.
(Example: Glucose — molecular: C₆H₁₂O₆, empirical: CH₂O)

What is lattice energy, how to compare lattice energy?

• Lattice energy (ΔHₗₐₜₜ) is the energy released when gaseous ions form an ionic solid, or the energy required to separate an ionic solid into gaseous ions.

• Equation:E=k\frac{Q_1Q_2}{r}

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• r = is the sum of the ionic radii of the cation and anion in the compound

• Q₁ and Q₂ = the charges of both ions

• E = Lattice Energy

Radius trend in Periodic Table

• Radius increase: Top—> Bottom 

• Radius decrease:Left—> right

• radius exponentially increases (so radius differences are larger for atoms lower on the periodic table)

comparing radius of elements

1) We can use the period table radius trend, BUT..

• If two elements are in a different row and column, the smallest is the one with less electrons

• If two electrons are in a different row and column and have the same number of electrons, the smallest is the one with more protons

How do you name a binary ionic compound when the cation is multivalent(could be any charge)?

Back (Answer):

• Identify the cation (metal) and its possible charges.

• Identify the anion (nonmetal) and its charge.

• Determine the charge of the cation that balances the anion.

• Write the cation name first, followed by the anion name.

• Indicate the cation’s charge with a Roman numeral in parentheses.

Example:

• FeCl₂ → Iron(II) chloride

• FeCl₃ → Iron(III) chloride

What are the charges of compounds typically?

they are formed to be neutral

(excluding the specific ones we are memorizing)

Elements that exist as a Diatomic Molecule

H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂

How do we name elements?

Molecular Compound Prefixes (Nonmetal + Nonmetal)

1 — mono- (omit “mono” on the first element)
2 — di-
3 — tri-
4 — tetra-
5 — penta-
6 — hexa-
7 — hepta-
8 — octa-
9 — nona-
10 — deca-

outliers for the roman numeral rule for ionic compounds

“Al, Zn, Sc — no Roman for me!”

• aluminum

• scandium

• Zinc

main group elemtns that still use roman numeral

• Tin(Sn)

• Lead(Pb)

• Antimony(Sb)

• Bismuth(Bi)

How do you identify a hydrocarbon?

• No oxygen, nitrogen, sulfur, or halogens present.

• Molecular formulas look like CₓHᵧ.

• Common types:

  • Alkane: single bonds only → CₙH₂ₙ₊₂

  • Alkene: one double bond → CₙH₂ₙ

  • Alkyne: one triple bond → CₙH₂ₙ₋₂

  • Aromatic (benzene rings): follow C₆H₆-type pattern
    ✅ Examples:

• CH₄ → methane (alkane)

• C₂H₄ → ethene (alkene)

• C₂H₂ → ethyne (alkyne)

What’s the difference between organic and inorganic compounds?

✅ Organic Compounds:

• Always contain carbon (C) (usually bonded to H, O, N, or S)

• Often found in living organisms

• Covalent bonding dominates

• Examples: CH₄, C₆H₁₂O₆, C₂H₅OH

✅ Inorganic Compounds:

• Usually do not contain carbon, or carbon isn’t bonded to hydrogen

• Often from nonliving sources (minerals, salts, metals)

• Often ionic bonding

• Examples: NaCl, H₂O, CO₂*, NH₃

🟡 Note: CO₂, CO, and carbonates (like CaCO₃) are inorganic, even though they have carbon.

What are the main functional groups to identify?

✅ Alkene (C=C) → double bond between carbons
✅ Alkyne (C≡C) → triple bond between carbons
✅ Alcohol (R–OH) → hydroxyl group on carbon
✅ Carboxylic Acid (R–COOH) → carbon with C=O and O–H
✅ Amine (C-N, C-NH-C, C-NH²) → nitrogen attached to carbon/hydrogen

How can you quickly recognize these functional groups in a molecule?

• Look for C=C → alkene

• Look for C≡C → alkyne

• Look for O–H → alcohol or acid

• If C=O and O–H on the same carbon → carboxylic acid

• Look for N attached to C/H → amine

what is a functional group?

• –OH → Alcohols

• –COOH → Carboxylic acids

• –NH₂ → Amines

• C=C → Alkenes

💡 Think of functional groups as the “active sites” of organic molecules — they decide how a molecule behaves.

formula mass

find the mass of the compound the give you… NOT THE MASS OF THE SIMPLEST RATIO VERSION OF THE COMPOUND

How do you determine a chemical formula given the ratios of each element?

• Convert each percent to grams(multiply by 100 g)

• convert to moles(via g/mol number for each element)

• balance moles!

Combustion analysis procedure

• find the number of C and H moles based on the H20 and C02 produces

• (if Oxygen in compound) find the moles of Oxygen in the element by subtracting the mass of the C and O by the total mass of the compound and then use that number to find the moles of oxygen via g/mol of oxygen

• balance the moles in the compound

Hydrocarbon

• Definition: Compounds made only of carbon (C) and hydrogen (H).

• Main Types:

  1. Alkanes – single bonds only (CnH₂n₊₂)

  2. Alkenes – at least one double bond (CnH₂n)

  3. Alkynes – at least one triple bond (CnH₂n₋₂)

  4. Aromatic – contain benzene rings (C₆H₆ type)