chapter1

What are valence electrons?

The outermost shell electrons of an atom.

What is the Aufbau principle?

Electrons fill lower energy atomic orbitals before higher energy ones.

What does Pauli’s exclusion principle state?

No more than two electrons can occupy the same orbital

What is Hund’s rule?

Every orbital in a subshell is singly occupied before any orbital is doubly occupied.

What is the Octet rule?

Atoms lose, gain, or share electrons to achieve 8 valence electrons (noble gas configuration).

What are exceptions to the Octet rule?

Hydrogen (2 electrons), electron-deficient molecules (like BeCl2), and expanded valence shell molecules (like PF5).

What is electronegativity?

The ability of an atom to attract shared electrons to itself.

What is electron affinity?

Energy released when an electron is added to a neutral gaseous atom.

What is ionization energy?

Energy required to remove an electron from a gaseous atom.

What type of elements form an ionic bond?

Reactive metals (low electronegativity) and reactive non-metals (high electronegativity).

What is an ionic bond?

The electrostatic attraction between oppositely charged ions (cations and anions).

What happens to ions in ionic bonding?

A metal loses electrons (becomes a cation) and a non-metal gains electrons (becomes an anion).

What condition favors a strong ionic bond?

A high electronegativity difference (usually greater than 1.8).

What is a covalent bond?

A bond formed by sharing one or more pairs of valence electrons between non-metal atoms.

Define a coordinate (dative) bond.

A bond where both shared electrons are donated by only one of the participating atoms.

Which covalent bond is the longest?

Single bond.

Which covalent bond is the strongest?

Triple bond.

What does VSEPR theory stand for?

Valence Shell Electron Pair Repulsion.

What determines the molecular shape in VSEPR theory?

The repulsion between electron pairs around the central atom.

What is the molecular shape of water (H2O)?

Bent or V-shaped.

What is a "giant covalent structure"?

A 3D network of atoms joined by covalent bonds (e.g., diamond, quartz).

Why does graphite conduct electricity?

It has delocalized (free-moving) electrons.

What are the three main types of intermolecular forces?

London dispersion forces, Dipole-dipole interactions, Hydrogen bonding.

What is the strongest intermolecular force?

Hydrogen bonding.

What is the weakest intermolecular force?

London dispersion forces.

When does hydrogen bonding occur?

When hydrogen is attached to F, O, or N and interacts with a lone pair on F, O, or N.

What are London dispersion forces caused by?

Temporary (instantaneous) dipoles due to electron motion.

What is the "sea of electrons" model?

A model of metallic bonding where positive metal ions are surrounded by free-moving valence electrons.

Why can metals conduct electricity?

Because valence electrons are delocalized and free-moving.

What is the bond angle in a tetrahedral geometry (e.g., CH4)?

109.5 degrees.

What is a "coordination number"?

The number of atoms or ions surrounding a central atom in a crystal lattice.

Why is CO2 non-polar?

It is linear, so individual bond dipoles cancel out.

What type of bond is formed between ammonia (NH3) and boron trifluoride (BF3)?

Coordinate (dative) bond.

What is a crystal lattice?

A geometric arrangement of points (ions) in a crystalline solid.

What is a "unit cell"?

The smallest repeating unit of a crystal lattice.

Name the three cubic unit cell types.

Simple cubic, Face-centered cubic (fcc), Body-centered cubic (bcc).

Metallic bonds are formed between what types of elements?

Metals only.

How does bond length change from single to triple bonds?

Single > Double > Triple (Longest to Shortest).

How does bond strength change from single to triple bonds?

Triple > Double > Single (Strongest to Weakest).

What is the shape of BeCl2 according to VSEPR theory?

Linear.

What is the shape of BF3 according to VSEPR theory?

Trigonal planar.

What is the shape of methane (CH4) according to VSEPR theory?

Tetrahedral.

What type of intermolecular force allows geckos to climb walls?

Van der Waals forces (specifically London dispersion forces).

What is a dipole?

A pair of charges equal in magnitude but opposite in sign, separated by a distance.

How are ionic bonds different from covalent bonds?

Ionic bonds involve transfer of electrons

What are the two types of van der Waals forces?

Dipole-dipole interactions and London dispersion forces.

What are ion-dipole interactions?

Electrostatic interaction between an ion and a polar molecule.

Does diamond conduct electricity?

No, it has no free-moving electrons.

Does solid NaCl conduct electricity?

No, ions are held in fixed positions and cannot move.

What is the primary intermolecular force in liquid water?

Hydrogen bonding.

Which bond type is stronger: Metallic bond or Ionic bond?

Ionic bond is generally stronger.

Which intermolecular force is found in all molecules and atoms?

London dispersion forces.

Which is the most polar bond: H-F, H-Cl, H-Br, or H-I?

H-F.

Which is the least polar bond: H-F, H-Cl, H-Br, or H-I?

H-I.

Name a compound with expanded valence shell.

PF5 or SF6.

Name an electron-deficient molecule.

BeCl2 or BF3.

Why is NaCl a 1:1 ratio?

Because the coordination number of Na+ is 6 and Cl- is 6, resulting in a 1:1 formula unit.

What is electroneutrality in ionic compounds?

Ionic compounds are neutral overall because electrons lost equal electrons gained.

What is the shape of a molecule with 2 bonds and 1 lone pair (AX2E)?

V-shaped (Bent).

What is the order of repulsion according to VSEPR?

Bonding pair-bonding pair < Bonding pair-lone pair < Lone pair-lone pair.

What are the three types of chemical bonding?

Ionic bonding, Covalent bonding, Metallic bonding.

Does chlorine (Cl2) have a dipole moment?

No, it is zero.

What is meant by 'bond length'?

The average distance between the nuclei of two bonded atoms.

What is meant by 'bond energy'?

The energy required to break a chemical bond.

Where can hydrogen bonding occur?

Between molecules containing H bonded to N, O, or F, and lone pairs on N, O, or F.

What type of bond forms NH4+ from NH3 and H+?

Coordinate bond.

What is "electrostatic attraction"?

The force holding oppositely charged ions together in ionic compounds.

What is "lattice energy"?

Energy released when ions in gas phase form a solid ionic lattice.

What do Lewis symbols represent?

Valence electrons in s and p orbitals of an atom.

Which bond is stronger: single covalent or coordinate?

They are equal strength once formed, but coordinate bonds are formed by one atom donating a pair.