Molecular Structure

What mostly determines chemical properties?

Valence electrons.

Why are inert gases generally unreactive?

They have filled outer s and p shells.

In Lewis notation, what does the chemical symbol represent?

The nucleus and inner electrons.

When are Lewis diagrams most useful according to the slides?

When considering s and p electrons.

How can atoms achieve a complete outer shell?

By losing or gaining electrons (ionic bonding) or sharing electrons (covalent bonding).

How is formal charge calculated conceptually?

Assign one electron from each shared pair to the atom, then add its unshared electrons, and compare with the neutral atom's valence electrons.

What are resonance structures?

Different Lewis diagrams used to represent bonding when one diagram alone does not adequately represent the molecule.

Does one resonance structure alone fully represent the true bonding according to the slides?

No. The true bonding lies between the resonance extremes.

When choosing between Lewis structures, what is the first preference?

The structure with the lowest magnitudes of formal charges.

If formal charge magnitudes are equal, which structure is preferred?

The one with the negative formal charge on the more electronegative atom.

What is VSEPR used to predict?

Molecular geometry or shape.

How does a multiple bond count in VSEPR?

A single, double, or triple bond counts as one electron domain.

What is the geometry with 2 electron groups and 0 lone pairs?

Linear, with a bond angle of 180°.

What is the geometry with 3 electron groups and 0 lone pairs?

Trigonal planar, with bond angles around 120°.

What is the molecular shape with 3 electron groups and 1 lone pair?

Bent or angular, with an angle less than 120°.

What is the geometry with 4 electron groups and 0 lone pairs?

Tetrahedral, with bond angles around 109.5°.

What is the molecular shape with 4 electron groups and 1 lone pair?

Trigonal pyramidal, with bond angles less than 109.5°.

What is the molecular shape with 4 electron groups and 2 lone pairs?

Bent or angular, with bond angles less than 109.5°.

What is the geometry with 5 electron groups and 0 lone pairs?

Trigonal bipyramidal, with angles around 90°, 120°, and 180°.

What is the shape with 5 electron groups and 1 lone pair?

Seesaw.

What is the shape with 5 electron groups and 2 lone pairs?

T-shaped.

What is the shape with 5 electron groups and 3 lone pairs?

Linear, with a bond angle of 180°.

What is the geometry with 6 electron groups and 0 lone pairs?

Octahedral, with bond angles of 90° and 180°.What is the shape of HCN?

What is the shape of CO₃²⁻?

Trigonal planar.

What is the shape of SO₂?

Bent or angular; the central sulfur has one single bond, one double bond, and one lone pair in the slide example.

What is the shape of CH₄?

Tetrahedral.

What is the shape of NH₃?

Trigonal pyramidal.

What is the shape of H₂O?

Bent or angular.

What is the polarity of a bent triatomic molecule according to the slides?

Polar, as illustrated by H₂O.What is hybridization?

What does molecular geometry tell us about electron pairs?

The directions in which bonding and nonbonding electron pairs are arranged.

What is the hybridization of carbon in CH₄?

sp³.

Which orbitals combine to form four sp³ hybrid orbitals?

One s orbital and three p orbitals.

What percentage s and p character does an sp³ orbital have?

25% s and 75% p.

What geometry is associated with sp³ hybridization in the slides?

Tetrahedral, with angles around 109.5°.

What is the hybridization associated with trigonal planar geometry?

sp².

Which orbitals combine to form three sp² hybrid orbitals?

One s orbital and two p orbitals; one p orbital remains unhybridized.

What percentage s and p character does an sp² orbital have?

About 33% s and 67% p.

What geometry is associated with sp hybridization?

Linear, with a bond angle of 180°.

Which orbitals combine to form two sp hybrid orbitals?

One s orbital and one p orbital.

What percentage s and p character does an sp orbital have?

50% s and 50% p.What is a sigma (σ) bond?

What type of bond is every single covalent bond?

A sigma (σ) bond.

What is a pi (π) bond?

A bond with electron density above and below the line joining the atom centres.

What bonds make up a double bond?

One sigma bond and one pi bond.

What bonds make up a triple bond?

One sigma bond and two pi bonds.

What is the hybridization of each carbon in ethylene (C₂H₄) according to the slides?

sp².

What bonds connect the two carbons in ethylene (C₂H₄)?

One sigma bond and one pi bond.

What is the hybridization of each carbon in acetylene (C₂H₂) according to the slides?

sp.

What bonds connect the two carbons in acetylene (C₂H₂)?

One sigma bond and two pi bonds.What is an electron domain?

How many electron domains does a single bond count as?

One.

How many electron domains does a double or triple bond count as?

One each.

How many electron domains does a lone pair count as?

One.

What is electrostatic attraction?

The force between electrically charged particles; opposite charges attract and like charges repel.

What does Coulomb’s law describe?

The force between two point charges; it is proportional to the product of their charges and inversely proportional to the square of the distance between them.

How do ionic bonds form according to the slides?

Electrons transfer from one atom to another, creating oppositely charged ions that attract electrostatically.

What happens when sodium reacts with chlorine to form NaCl?

Sodium loses an electron and chlorine gains an electron, forming Na⁺ and Cl⁻ that attract one another.

What affects the physical properties of an ionic compound?

The strength of the electrostatic attraction between its ions.