Molecules and Compounds - AP Chemistry

The Valence Bond theory states that covalent bonds are formed from atomic orbital overlap while the Molecular Orbital theory is the mathematical combination of atomic orbitals to produce anti bonding and bonding orbitals.

Hybridization occurs through combining atomic orbitals, a concept consistent with Valence Bond theory. Common bonds found in Valence Bond hybridization are sigma and pi bonds which overlap end-to-end or side-to-side respectively. Orbitals are combined in Molecular Orbital theory, producing either bonding or anti bonding orbitals. Molecular Orbital theory shows the destructive or constructive interference of sigma and pi bonds (displayed through bonding and anti bonding orbitals).

Start by drawing the Lewis structure of . has valence electrons.

Since the nitrogen has oxygen atoms bonded to it and a lone pair, the steric number must be . From that, we know that it must have sp2 hybridization.

Look at each of the carbon atoms in the chain. Each carbon atom has other atoms bonded to it. This means that the steric number of each carbon is . Thus, the only type of hybridization found in this molecule is sp2.

Start by counting the number of atoms the nitrogen is bonded to. It has bonded atoms. The nitrogen also has a lone pair. This means the steric number of the nitrogen is . Thus, it must have hybridization.

Hydrazine is a polar compound that possesses the requirements for hydrogen bonding: an "acidic hydrogen" (a hydrogen bonded to a highly electronegative atom such as oxygen, nitrogen or fluorine) and the presence of a lone pair. Both Nitrogen atoms in hydrazine have lone (unshared) electron pairs, and all four hydrogen atoms are "acidic," making hydrazine a candidate for intermolecular hydrogen bonding.

The partial negative and positive charges on a water molecule allow it to be attracted to other polar water molecules, which creates the cohesive nature of water and contributes to its high surface tension and heat capacity. London dispersion and Van der Waals forces are significantly weaker than hydrogen bonding. Additionally, ionic bonding only occurs intramolecularly, so it has little effect on the intermolecular properties of water.

A covalent bond is one between two nonmetals, while an ionic bond is formed between a metal and a nonmetal. Covalent bonds also do not dissociate in aqueous solution to form cations and anions; this is a characteristic of ionic bonds. For example, represents a bond between a metal () and a nonmetal (), and it dissociates in aqueous solution to form a cation () and an anion (). In contrast, represents a bond between two nonmetals, and it does not dissociate in aqueous solution. Ionic compounds are also good conductors of electricity, while covalent compounds are not. This is because moving electrons are required in order to conduct electricity. When dissolved in aqueous solution, ions are free to move and thus conduct electricity. Covalent bonds have localized electrons, which cannot move and thus cannot conduct electricity well.

A covalent bond is a bond between two nonmetals, in which electrons are shared. This means that cannot be the correct answer, as sodium is a metal. In fact, is a classic example of an ionic compound.

A polar covalent bond is a bond between two nonmetals in which one nonmetal is more electronegative than the other, pulling the shared electrons toward itself. This occurs in ; chlorine is much more electronegative than hydrogen and pulls the shared electrons toward itself. This gives chlorine a partial negative charge and hydrogen a partial positive charge. is also an example of a polar covalent bond; oxygen is much more electronegative than hydrogen, and each oxygen in a water molecule pulls the shared electrons toward itself. This gives oxygen a partial negative charge and hydrogen a partial positive charge.

A nonpolar covalent bond is a bond between two nonmetals in which electrons are shared equally between the nonmetals. This occurs when the two nonmetals are of equal electronegativity. As the atoms of have the same identity (chlorine), they have the same electronegativity. Thus, electrons are shared equally between the two chlorine atoms--in a nonpolar covalent bond.

Oxygen has a valence of 6, meaning it is looking to form two covalent bonds to complete its octet. Thus, exists as a diatomic molecule joined by a double covalent bond. and are held together by single covalent bonds, and is held together by a triple covalent bond.

Dipole-dipole interactions are the weakest because they are the result of attractions between weak partial charges

Hydrogen bonds are a special type of dipole-dipole interaction, but they are much stronger.

An ionic bond is the result of the complete transfer of electrons from on atom to another. This results in a positive charge on one atom and a negative charge on the other. The charges on these ions are much stronger than in dipoles. The two oppositely charged atoms are held together by electrostatic attraction.

Atoms that are part of a covalent bond share electrons. This makes the atoms harder to separate and, therefore, the bond is very strong.

For this question, we're asked to determine which answer choice represents a compound with a total of six covalent bonds.

To answer this, we'll need to know the structure of each of the compounds. Moreover, it's important to remember that double bonds count as two covalent bonds.

Both sulfuric acid and phosphoric acid have a total of eight covalent bonds, while nitric acid has five. Carbonic acid is the only one shown that contains six covalent bonds, making it the correct answer.

Molarity has no determination in whether an acid or base is strong or weak. Rather, molarity specifies the concentration of hydroxide or hydrogen ions in a solution. Weak Acids do not completely dissociate in water, while strong acids do. Polyprotic acids, those with more than one proton to donate, do not necessarily determine if an acid is strong (e.g. hydrochloric acid is an example of a strong, monoprotic acid).

is an ionic compound because it is composed of a metal and a nonmetal.

is a molecular compound because it consists of a nonmetal connected to another nonmetal.

Xenon is an atomic element because its elemental form consists of one atom.

In order to answer this question correctly, you must remember the different types of intermolecular forces and their effects.

only contains London dispersion forces. Since it is a smaller molecule compared to the others, it cannot have the highest boiling point.

also only contains London dispersion forces. However, since it is a bigger molecule, it will have a higher boiling point than .

While contains both London dispersion forces and dipole-dipole interactions, it lacks hydrogen boding as the fluorine atom is attached directly to the second carbon.

has the highest boiling point because it contains London dispersion forces, dipole-dipole interactions, and hydrogen bonding.

A hydrogen bond refers to the attraction between a hydrogen attached to an electronegative atom of one molecule and an electronegative atom of another molecule. The atoms which commonly form hydrogen bonds are oxygen, nitrogen, and fluorine, which are very electronegative. When a hydrogen bond forms between hydrogen and one of these three atoms, hydrogen gains a partial positive charge while the electronegative atom gains a partial negative charge. Carbon is not a very electronegative atom and thus cannot form a hydrogen bond.

London dispersion forces are the weakest of the three. Every molecule is composed of electrons, which are free to move around. This can create a temporary charge, on any molecule, at any time. When two molecules come close together, their varying charges can orient such that one end of a molecule may be slightly positive, while the end of a nearby molecule may be slightly negative. This leads to a slight attraction between the two molecules, called London dispersion forces until they move around again. This is a weak, temporary force.

Dipole-dipole interactions develop when polar compounds line up and are attracted to each other. These forces are stronger than London dispersion forces due to the permanency of the dipoles, but weaker than hydrogen bonds.

Hydrogen bonds are the strongest force of the three. The name refers to the attractive force between the hydrogen attached to one electronegative atom (usually oxygen, nitrogen, or fluorine) and an electronegative atom of a different molecule. The electronegative atom gains a partial negative charge, while the hydrogen gains a partial positive charge. These forces are responsible for many of the qualities of water.

Drawing the Lewis Diagrams for these molecules reveals that the C-N bond in is a triple covalent bond, whereas the C-N bonds in and are double covalent bonds and the C-N bond in is a single covalent bond. Triple covalent bonds between two given atoms are always stronger than double bonds between these same two atoms, and similarly double bonds are even stronger than single bonds. Bond length is inversely related to bond strength; therefore a shorter bond is a stronger bond, and triple covalent bonds are shorter than either double or single covalent bonds. Thus, the C-N bond in is the shortest in length.

Ne is the only element that does not exist as a diatomic molecule because it is a noble gas, meaning it has a stable resting valence electron configuration, and exists simply as an atomic molecule. By comparison, N, O, and Cl can all achieve stable states by forming a diatomic molecule. and are held together by a single covalent bond, or shared electron pair. is held together by sharing two electron pairs (two covalent bonds), and by sharing three pairs.