Chem Vespr, simple shapes

The shape of a molecule depends on what?

The number of bonding pairs and lone pairs of electrons around the central atom

What theory explains molecular shapes?

Valence Shell Electron Pair Repulsion (VSEPR) theory

What shape does a molecule with 2 bonding regions and no lone pairs have?

Linear

What shape does a molecule with 3 bonding pairs and no lone pairs have?

Trigonal planar

What shape does a molecule with 4 bonding pairs and no lone pairs have?

Tetrahedral

What shape does a molecule with 3 bonding pairs and 1 lone pair have?

Pyramidal

What shape does a molecule with 2 bonding pairs and 2 lone pairs have?

Non-linear (bent)

What shape does a molecule with 5 bonding pairs and no lone pairs have?

Trigonal bipyramidal (e.g.

What shape does a molecule with 6 bonding pairs and no lone pairs have?

Octahedral

According to VSEPR theory

what causes molecular shapes?

Which type of electron pair repulsion is strongest?

Lone pair–lone pair > lone pair–bond pair > bond pair–bond pair

How are double and triple bonds treated in VSEPR theory?

As one region of electron density

Define electronegativity.

The ability of an atom to attract bonding electrons in a covalent bond toward itself

What scale is used to measure electronegativity?

The Pauling scale

Which element is the most electronegative?

Fluorine (4.0 on the Pauling scale)

What factors affect electronegativity?

Nuclear charge

How does electronegativity change across a period?

It increases across a period

How does electronegativity change down a group?

It decreases down a group

When two atoms have the same electronegativity

what kind of bond forms?

When two atoms have different electronegativities

what kind of bond forms?

What symbol shows bond polarity direction?

→ with a cross at the δ⁺ end and arrow toward δ⁻

What is a dipole moment?

A measure of bond polarity showing charge separation

Why is CH₃Cl polar but CCl₄ nonpolar?

CH₃Cl dipoles don’t cancel; CCl₄ dipoles do due to symmetry

What are intramolecular forces?

Forces within a molecule (e.g.

What are intermolecular forces?

Forces between molecules

List the three types of intermolecular forces.

Induced dipole–dipole

What causes London dispersion forces?

Temporary dipoles from moving electron clouds

How does molecular size affect London forces?

Larger molecules with more electrons have stronger London forces

What are permanent dipole–dipole forces?

Attractions between molecules with permanent dipoles (e.g.

Which is stronger: induced dipole–dipole or permanent dipole–dipole?

Permanent dipole–dipole (in small molecules with similar electron counts)

What elements are involved in hydrogen bonding?

Hydrogen bonded to O

Why is hydrogen bonding strong?

The H atom becomes highly δ⁺ and bonds with a lone pair on another O

What properties of water are caused by hydrogen bonding?

High melting/boiling points

Why is ice less dense than water?

Molecules form an open hydrogen-bonded lattice

Why does iodine sublime easily?

It has weak induced dipole–dipole (van der Waals) forces

What is the general rule for solubility?

“Like dissolves like” — polar dissolves in polar

Why does ethanol dissolve in water but hexanol does not?

Ethanol’s polar OH group dominates; hexanol’s long nonpolar chain reduces solubility

Why do most covalent substances not conduct electricity?

They lack free-moving charged particles

Which covalent structures can conduct electricity?

Some giant covalent structures with delocalised electrons (e.g.