CHEM 1340 Molecules and Compounds Notes

Flashcards covering introduction to compounds, molecular vs network covalent bonding, ionic bonding, empirical vs molecular formulas, charge prediction, and detailed chemical nomenclature rules.

What is a chemical compound?

A chemical combination of two or more elements that forms a pure substance and does not retain the properties of the elements that compose it.

What is a molecule?

The smallest stable particle of a substance that has the composition of that substance, typically referring to molecular compounds.

What is a formula unit?

The smallest collection of cations and anions that have the composition of an ionic compound.

What formula unit composition is present in $(NH_4)_2CO_3$?

Two $NH_4^+$ ions and one $CO_3^{2-}$ ion.

What are molecular covalent compounds and what are their physical properties?

Compounds consisting of discrete molecules in which atoms are bonded together by sharing electrons, featuring relatively low melting and boiling points, and existing as gases, liquids, or solids at room temperature.

What are network covalent compounds and what are their physical properties?

Compounds that exist as crystals in which atoms are bonded together by sharing electrons, featuring very high melting and boiling points, and always existing as solids at room temperature.

What are two examples of network covalent compounds given in the notes?

$SiO_2$ (silicon dioxide, quartz) and $SiC$ (silicon carbide, used in sand paper).

What physical properties characterize ionic compounds?

They have high melting and boiling points and are always solids at room temperature.

What is the difference between a molecular formula and an empirical formula?

A molecular formula shows the number of atoms of each element in a molecule, while an empirical formula gives the simplest ratio of atoms of each element in a compound.

What is the empirical formula for benzene ($C_6H_6$)?

$$CH$$

How is the ionic charge predicted for monatomic cations formed from metals in Groups IA, IIA, or IIIA?

The cation charge is equal to the group number ($C = G$).

What is the formula used to calculate the ionic charge for monatomic anions in Groups VA, VIA, or VIIA?

$\text{Charge} = G - 8$, where $G$ is the group number.

What is the chemical formula for the ionic compound containing $Fe^{3+}$ and $CO_3^{2-}$?

$$Fe_2(CO_3)_3$$

What is the chemical formula for the binary ionic compound containing $Sr$ and $Br$?

$$SrBr_2$$

How is $Hg_2^{2+}$ named using the Oxidation Number Method versus the Historical Method?

In the Oxidation Number Method it is named mercury(I) ion, and in the Historical Method it is named mercurous ion.

What is the general form and an example of naming a halogen oxyanion with 4 oxygens ($XO_4^-$)?

General form: [per- + element stem + -ate] [ion]; Example: $IO_4^-$ (periodate ion).

What rule applies to numerical prefixes in binary covalent compounds when an element name begins with a vowel?

The last letter is dropped from prefixes ending in 'a' or 'o', but not from prefixes ending in 'i'.

What is the correct binary covalent compound name for $N_2O_5$?

Dinitrogen pentoxide

How does the name of pure $HCl$ differ from its name when in aqueous solution?

As a pure compound it is named hydrogen chloride, whereas in aqueous solution it is named hydrochloric acid.

What are the common names for $CH_4$, $NH_3$, $CH_3OH$, $C_2H_4$, $C_2H_6$, $H_2O$, $CH_2O$, and $C_2H_2$?

Methane ($CH_4$), ammonia ($NH_3$), methanol ($CH_3OH$), ethylene ($C_2H_4$), ethane ($C_2H_6$), water ($H_2O$), formaldehyde ($CH_2O$), and acetylene ($C_2H_2$).

What rule determines whether an aqueous oxyacid name ends in '-ous acid' or '-ic acid'?

Use '-ous' for the acid if the anion name ends in '-ite', and use '-ic' for the acid if the anion name ends in '-ate'.

Why are hydrogen nitrite ($HNO_2$) and hydrogen sulfite ($H_2SO_3$) noted specifically in the pure compound list for oxyacids?

They are not stable in pure form and exist only in solution.