Presentation: Chapters 2 Chemical Context of Life

Atom Basics

Atomic Structure

Atomic mass vs. Atomic Weight

Isotopes- Radioactive tracers

Intramolecular Forces

Bonding Forced WITHIN (Intra-) molecules

Covalent bonding- polar or non polar

Ionic bonding

Covalent Bonding

Sharing electrons

May be polar or non polar

Based on electronegativity= pull on electrons (affinity for e-)

Nonpolar= Atoms have equal electronegativity

Electrons are shared equally

ex. carbon and hydrogen, diatomic molecules

Polar= One atom has higher electronegativity

Electrons closer to one atom, partially negative

ex: oxygen and hydrogen

Examples

Polar Covalent Bond- Water

Oxygen has greater electronegativity

Electrons are drawn closer

Oxygen is now partially negative and hydrogens are partially positive

Polar Covalent Bonding

Non-polar Covalent Bonding

Ionic Bonding

Atoms gain (-) or lose (+) electrons to achieve a full outer (valence) shell

Oppositely charged ions (cation/anion) attract one another

A metal and a nonmetal

Usually forms a lattice pattern

Stronger than covalent bonding

Intermolecular Forces (IMFs)

Bonding BETWEEN (Inter-) molecules

Hydrogen Bonding

Dipole-dipole

Van der Waals forces

Hydrogen “Bond”/Interaction

Forms between two polar molecules

Hydrogen bonded to N, O, F the bonded to another polar molecule

Partial charges of one molecule are attracted to the opposite charges of another

Ex. water and ammonia

Other IMFs

Van der Waals attractions

Weak IMFs caused by changing dipoles

Gecko Fingers