Chemistry 1: Chemical Bonding, Molecular Geometry, and Intermolecular Forces

Comprehensive practice flashcards covering chemical bonding, ionic and covalent compound nomenclature, VSEPR molecular geometry, bond and molecular polarity, intermolecular forces, physical properties, and real-world industrial and sustainability applications.

What is a chemical bond, and why do atoms form bonds?

A chemical bond is an attractive force that holds atoms or ions together to reach a more stable, lower-energy arrangement.

What are valence electrons, and how do they correspond to the periodic table for representative elements?

Valence electrons are the electrons in the outermost energy shell that participate in chemical bonding. For representative elements (Groups 1A–7A), the group number corresponds directly to the number of valence electrons.

What is the Octet Rule, and what does the Greek root of the word mean?

The Octet Rule states that atoms tend to gain, lose, or share electrons to attain eight valence electrons (mimicking noble gases). It comes from the Greek word "okto," meaning "eight."

Who developed the Lewis electron-dot structure system?

American chemist Gilbert Lewis.

What are the four exceptions to the Octet Rule mentioned in the reviewer?

1. Duet Rule: Hydrogen ($\text{H}$) and Helium ($\text{He}$) are stable with two electrons.
2. Incomplete Octet: Beryllium ($\text{Be}$) and Boron ($\text{B}$) compounds (e.g., $\text{BF}_3$).
3. Odd-Electron Species: Radicals containing an odd number of electrons (e.g., $\text{NO}$).
4. Expanded Octet: Period 3 and beyond elements that accommodate more than eight electrons using available d-orbitals (e.g., $\text{SF}_6$, $\text{PCl}_5$).

How do ionic and covalent bonding differ in terms of electron behavior and element types?

Ionic bonding involves the transfer of electrons (loss and gain) between a metal and a nonmetal, forming cations and anions. Covalent bonding involves the sharing of electron pairs between nonmetals.

How do ionic and molecular covalent compounds compare in electrical conductivity?

Ionic compounds conduct electricity when molten or dissolved in water because their ions become mobile, but do not conduct as solids. Molecular covalent compounds are generally poor conductors because they lack mobile charged particles.

Why are crystalline ionic compounds brittle?

Shifting layers in the crystal lattice can place ions of like charges next to one another, resulting in strong electrostatic repulsion and fracture.

Where in the Philippines is sodium chloride ($\text{NaCl}$) commercially harvested through seawater evaporation?

In the salt farms of Pangasinan and Occidental Mindoro.

What ionic compound is found in limestone and marble and used in cement production such as Rizal Portland?

Calcium carbonate ($\text{CaCO}_3$).

What are the chemical formula and everyday uses of sodium bicarbonate?

Formula: $\text{NaHCO}_3$. Common uses: baking soda, antacids, and cleaning products.

Which ionic compounds are cited as agricultural fertilizers?

Ammonium nitrate ($\text{NH}_4\text{NO}_3$) and potassium nitrate ($\text{KNO}_3$).

Which ionic compounds are used in water treatment?

Aluminum sulfate ($\text{Al}_2(\text{SO}_4)_3$) and calcium hypochlorite ($\text{Ca}(\text{HClO})_2$).

What is the common name and application of magnesium sulfate ($\text{MgSO}_4$)?

Epsom salt; used in agriculture for soil treatment and in bath preparations.

What are the cation, anion, chemical formula, and IUPAC name for compound #1 in the practice drill?

Cation: $\text{NH}_4^+$, Anion: $\text{NO}_3^-$, Formula: $\text{NH}_4\text{NO}_3$, Name: Ammonium nitrate.

What is the IUPAC name and component ions of $\text{Ba}(\text{ClO}_4)_2$?

Name: Barium perchlorate. Cation: $\text{Ba}^{2+}$, Anion: $\text{ClO}_4^-$.

What are the chemical formula and component ions for Nickel(III) carbonate?

Formula: $\text{Ni}_2(\text{CO}_3)_3$. Cation: $\text{Ni}^{3+}$, Anion: $\text{CO}_3^{2-}$.

What is the IUPAC name and component ions for $\text{FeF}_2$?

Name: Iron(II) fluoride. Cation: $\text{Fe}^{2+}$, Anion: $\text{F}^-$.

What is the chemical formula and component ions for Sodium sulfide?

Formula: $\text{Na}_2\text{S}$. Cation: $\text{Na}^+$, Anion: $\text{S}^{2-}$.

What chemical formula and name result from combining $\text{Pb}^{2+}$ and $\text{Cl}^-$?

Formula: $\text{PbCl}_2$. Name: Lead(II) chloride.

What is the IUPAC name and cation for $\text{CoCrO}_4$ containing $\text{CrO}_4^{2-}$?

Name: Cobalt(II) chromate. Cation: $\text{Co}^{2+}$.

What are the chemical formula and component ions for Potassium nitride?

Formula: $\text{K}_3\text{N}$. Cation: $\text{K}^+$, Anion: $\text{N}^{3-}$.

What are the anion and IUPAC name for $\text{Li}_2\text{O}$ containing $\text{Li}^+$?

Anion: $\text{O}^{2-}$. Name: Lithium oxide.

What is the chemical formula and component ions for Copper(I) acetate?

Formula: $\text{CuC}_2\text{H}_3\text{O}_2$ (or $\text{CuCH}_3\text{COO}$). Cation: $\text{Cu}^+$, Anion: $\text{C}_2\text{H}_3\text{O}_2^-$.

What are the chemical formulas for iodine trifluoride, diphosphorus pentoxide, and tetraphosphorus trisulfide?

Iodine trifluoride: $\text{IF}_3$ Diphosphorus pentoxide: $\text{P}_2\text{O}_5$ Tetraphosphorus trisulfide: $\text{P}_4\text{S}_3$.

What is the IUPAC name for the hydrated salt $\text{ZnCl}_2 \cdot 6\text{H}_2\text{O}$?

Zinc chloride hexahydrate.

What is the chemical formula for barium hydroxide octahydrate?

$\text{Ba}(\text{OH})_2 \cdot 8\text{H}_2\text{O}$.

How do the names of $\text{HCl}(aq)$ and $\text{HCl}(g)$ differ?

$\text{HCl}(aq)$ is named as a binary acid: Hydrochloric acid. $\text{HCl}(g)$ is named as a binary molecular compound: Hydrogen chloride.

What is the name of $\text{HNO}_2(aq)$ and how is its acid suffix determined?

Nitrous acid. Because its polyatomic anion is nitrite ($\text{NO}_2^-$), the ending "-ite" changes to "-ous acid."

What is the IUPAC name for $\text{N}_2\text{O}_4$?

Dinitrogen tetroxide.

What rule applies when a Greek numerical prefix ending in "a" or "o" is attached to "oxide"?

Drop the final "a" or "o" of the prefix (e.g., "monoxide" instead of "monooxide"; "decoxide" instead of "decaoxide").

What is electronegativity (EN) and what are its periodic table trends?

Electronegativity is how strongly an atom attracts shared bonding electrons in a chemical bond. On the Pauling scale ($0.7$ to $4.0$), it increases across a period (left to right) and increases up a group. Fluorine has the highest EN at $4.0$.

What are the threshold ranges of $\Delta\text{EN}$ used to determine bond types?

$\Delta\text{EN} = 0.0 - 0.4$: Nonpolar covalent $\Delta\text{EN} = 0.5 - 1.7$: Polar covalent $\Delta\text{EN} > 1.7$: Ionic.

Using class EN values (Mg = 1.2, O = 3.5), what is the $\Delta\text{EN}$ and bond type for the $\text{Mg}-\text{O}$ bond in $\text{MgO}$?

$\Delta\text{EN} = |3.5 - 1.2| = 2.3$. Because $2.3 > 1.7$, it is classified as ionic.

Using class EN values (C = 2.5, H = 2.1), what is the $\Delta\text{EN}$ and bond type for the $\text{C}-\text{H}$ bond in $\text{CH}_3\text{COOH}$?

$\Delta\text{EN} = |2.5 - 2.1| = 0.4$. It falls in the $0.0 - 0.4$ range and is classified as nonpolar covalent.

How are bond dipole vectors drawn?

A bond dipole vector points from the electropositive atom ($\delta^+$) to the electronegative atom ($\delta^-$). The tail ($$+$) sits on the electropositive atom and the arrowhead points toward the electronegative atom.

What is the core premise of VSEPR theory, and what does the acronym stand for?

Valence Shell Electron Pair Repulsion. Electron pairs around the central atom repel each other and spread out as far apart as possible to minimize electrostatic repulsion, setting the ideal geometry.

In $AX_mE_n$ notation, what do $A$, $X$, $m$, $E$, and $n$ represent?

$A$ = central atom; $X$ = surrounding (bonded) atom; $m$ = number of surrounding atoms; $E$ = nonbonding valence electron group (lone pair); $n$ = number of lone pairs.

What are the ideal electron pair geometries for total electron pair counts of 2, 3, 4, 5, and 6?

2 pairs: Linear 3 pairs: Trigonal planar 4 pairs: Tetrahedral 5 pairs: Trigonal bipyramidal 6 pairs: Octahedral.

Why do lone pairs reduce bond angles compared to ideal geometries?

Lone pairs exert greater electrostatic repulsion than bonding pairs, so they push bonded electron pairs closer together and squeeze the bond angles.

How do the bond angles of $\text{CH}_4$, $\text{NH}_3$, and $\text{H}_2\text{O}$ illustrate the effect of lone pairs?

$\text{CH}_4$ ($AX_4$, 0 lone pairs) has bond angles of $109.5^\circ$. $\text{NH}_3$ ($AX_3E$, 1 lone pair) is squeezed to $107^\circ$. $\text{H}_2\text{O}$ ($AX_2E_2$, 2 lone pairs) is squeezed to $104.5^\circ$.

What are the molecular shapes and ideal bond angles for 5-electron-pair species: $AX_5$, $AX_4E$, $AX_3E_2$, and $AX_2E_3$?

$AX_5$: Trigonal bipyramidal ($90^\circ, 120^\circ, 180^\circ$) $AX_4E$: Seesaw ($\sim 90^\circ, \sim 120^\circ$) $AX_3E_2$: T-shaped ($\sim 90^\circ$) $AX_2E_3$: Linear ($180^\circ$).

What are the molecular shapes and bond angles for 6-electron-pair species: $AX_6$, $AX_5E$, and $AX_4E_2$?

$AX_6$: Octahedral ($90^\circ, 180^\circ$) $AX_5E$: Square pyramidal ($90^\circ, 180^\circ$) $AX_4E_2$: Square planar ($90^\circ, 180^\circ$).

What is the key difference between bond polarity and molecular polarity?

Bond polarity applies to a single individual bond based solely on $\Delta\text{EN}$. Molecular polarity applies to the entire molecule and depends on both bond dipoles and the 3D molecular geometry via vector addition.

Why is $\text{CO}_2$ a nonpolar molecule even though its $\text{C}-\text{O}$ bonds are polar?

$\text{CO}_2$ is linear ($AX_2$) and symmetrical; the two equal $\text{C}=\text{O}$ bond dipole vectors point in opposite directions and cancel out, giving a net dipole moment of zero ($\mu = 0$).

Why is $\text{CCl}_4$ nonpolar while $\text{CH}_2\text{Cl}_2$ is polar, even though both have tetrahedral geometry?

In $\text{CCl}_4$, all four surrounding atoms are identical chlorine atoms, so the dipole vectors cancel symmetrically. In $\text{CH}_2\text{Cl}_2$, the surrounding atoms differ, resulting in an asymmetrical dipole distribution that creates a net dipole moment.

Why is $\text{XeF}_4$ nonpolar despite having lone pairs on the central atom?

$\text{XeF}_4$ has an $AX_4E_2$ square planar shape where the two lone pairs sit directly opposite each other ($180^\circ$), allowing all dipole vectors to cancel out symmetrically.

How do intramolecular forces differ from intermolecular forces (IMFs)?

Intramolecular forces are strong chemical bonding forces (ionic or covalent) within a molecule that determine chemical properties. Intermolecular forces are weaker attractions between separate molecules that determine physical properties.

What causes London dispersion forces (LDF), and where do they occur?

LDFs are caused by random fluctuations in electron distribution that create temporary instantaneous dipoles, which induce dipoles in neighboring molecules. They occur in all atoms and molecules and are the only IMFs present in nonpolar substances.

Why does $n$-pentane have a higher boiling point ($36.1^\circ\text{C}$) than neopentane ($9.5^\circ\text{C}$) even though both have the formula $\text{C}_5\text{H}_{12}$?

$n$-Pentane has an elongated chain structure that provides more surface contact points for dispersion forces to act, whereas neopentane is compact and spherical, offering fewer contact points.

What are the structural requirements for hydrogen bonding, and what are common examples?

A hydrogen atom must be directly bonded to a small, highly electronegative atom: Nitrogen ($\text{N}$), Oxygen ($\text{O}$), or Fluorine ($\text{F}$). Examples include $\text{H}_2\text{O}$, $\text{NH}_3$, $\text{HF}$, methanol ($\text{CH}_3\text{OH}$), ethanamide ($\text{CH}_3\text{CONH}_2$), and adenine-thymine DNA base pairs.

What is an ion-dipole force, and how do water molecules orient around $\text{Na}^+$ and $\text{Cl}^-$ ions?

An attraction between a full ion charge and the dipole of a polar molecule. The partial negative ($\delta^-$) oxygen ends of water orient toward $\text{Na}^+$, while the partial positive ($\delta^+$) hydrogen ends orient toward $\text{Cl}^-$.

Rank the four intermolecular forces in order from weakest to strongest.

London Dispersion Forces < Dipole-Dipole Forces < Hydrogen Bonding < Ion-Dipole Forces.

What type(s) of intermolecular forces act in $\text{PCl}_3$, $\text{N}_2$, and $\text{HF}$?

$\text{PCl}_3$: Dipole-dipole and dispersion (polar trigonal pyramidal molecule) $\text{N}_2$: Dispersion only (nonpolar diatomic molecule) $\text{HF}$: Hydrogen bonding, dipole-dipole, and dispersion.

How does increasing IMF strength affect surface tension, viscosity, boiling point, and melting point?

All four properties increase ($\uparrow$), because stronger attractive forces cause particles to stick together more tightly.

How does increasing IMF strength affect vapor pressure and volatility?

Both properties decrease ($\downarrow$), because stronger attractions make it harder for surface particles to escape into the gas phase.

What is the memory trick provided in the reviewer for IMF property trends?

Things that require sticking go UP (surface tension, viscosity, boiling point, melting point); things that require escaping go DOWN (vapor pressure, volatility). Vapor pressure and volatility always move together.

What is the complete conceptual chain connecting molecular features to sustainable product design?

Molecular Structure $\rightarrow$ Molecular Polarity $\rightarrow$ Intermolecular Forces $\rightarrow$ Physical Properties $\rightarrow$ Sustainable Product Design.

To formulate a cleaner that reduces evaporation and volatile organic compound (VOC) emissions, should a chemist choose a solvent with stronger or weaker IMFs?

Stronger IMFs, because stronger attractions lower volatility and vapor pressure, reducing particle escape and evaporation into the air.