QP 1.4 Chemical Energy and Intermolecular Forces

Electrons exist in

a probability cloud around a proton and neutron center

Atomic number

The number of protons in an atom

represented as Z

Electronegativity

How strongly an element attracts electrons

Stoichiometry

What molecules are made of (chemical formulas)

Covalent bonds

When two elements share electrons

Ionic bonds

Form from redox reactions

An interaction between positive and negative ions as a result of electron donation

Hydrogen Bond

weak, attraction between atoms in polar covalent bonds

Hydrogen and another atom

This is why lipids form bilayers

Form between hydrophilic molecules

When are atoms most stable

When they have a full orbital

Single bonds can freely ____ while double bonds are more ____

rotate

constrained

How do polar covalent bonds form

Form from uneven electron sharing due to a difference in electronegativity

Molecule shape must also permit asymmetrical electron sharing ( O=C=O isn’t polar because it is symmetric)

Hydrophobic molecules have no ____ bonds and can’t form _____ bonds

polar

hydrogen

True or false: hydrogen bonds are too weak to hold structures together

False, they do help hold structures together

Isomers

When two molecules have the same atoms but different arrangements

Structural isomer

When two molecules with the same atoms have different connections between the atoms

Stereoisomers

When two molecules have atoms with the connectivity but different 3D arrangements

Geometric isomer

A type of stereoisomer where the 3D arrangement is flip flopped around a double carbon bond

Cis: when H is on the same side

Trans: when H is on the opposite side

Optical Isomer

a type of stereoisomer where connection is different in molecules with a carbon with 4 groups attached

They are chiral (mirror images, left vs right handed)

Enantiomers

Mirror image optical isomers, when everything is inverted

Diastereomers

An optical isomer that has at least one inversion but is not a perfect mirror image