Lecture 1

Back to Basics!

Basic unit of elements

1. protons (+) and neutrons (-) make up the nucleus

2. electrons (-) travel around outer shells

3. protons and electrons are attracted to one another

Ions are charged atoms

Atoms form molecules

All atoms of an element have the same number of protons

Isotopes are two atoms of an element that have the same number of protons, different number of neutrons.

Radioactive isotopes decay spontaneously, giving off particles and energy.

Example: Doubly Labeled Water

Elements

Definition: Pure chemical substances consisting of one type of atom distinguished by its atomic number (the number of protons in its nucleus)

Three types of elements

1. metals (ex. Na)

2. metalloids (ex Si)

3. non-metals (ex. Cl)

*chemical behavior is determined by distribution of e- in valence shell*

Eight Essential Elements

Nitrogen (N)

Phosphorus (P)

Sodium (Na)

Potassium (K)

Calcium (Ca)

Magnesium (Mg)

Sulfur (S)

Chlorine (Cl)

Trace Elements (minor essential):

There are tons, but the most common trace elements are Selenium (Se), Chromium (Cr), Manganese (Mn) and Molybdenum (Mo)

Electronegativity: the ability of an atom to attract (pull) electrons towards itself.

Affected by:

- atomic number (protons)

- distance of valence electrons from nucleus

Valence electrons (yellow dots) are in the valence (outermost) shell.

the chemical behavior of atoms is mostly determined by valence e-
atoms with incomplete valence shells can share (covalent) or transfer (ion) with other atoms
held together by chemical bonds
valence shell has the highest energy levels. Energy levels in shells decrease as you get closer to the nucleus

Molecular Shape and Function

Shape is determined by position of the atoms valence orbitals

Similar shape = similar biological function

Interaction occurs based on molecular shape

Chemical Bonds

1) Covalent

strongest bonds
seen in organic molecules such as carbon
atoms SHARE electrons
- non polar: atoms share electrons equally (ex H2)
- polar: atoms share electrons unequally, has charged "poles" (ex H2O)

2)Ionic

atoms TRANSFER electrons
resulting ions are attracted to one another
ionic molecules are soluble in water

3)Intramolecular Forces

Hydrogen Bonds

H atom covalently bonded to an N, O, or F atom
polar H bonds are water soluble

Van Der Waals Interactions

e- distributed asymmetrically can result in "hot spots" of positive or negative charge"
VDW interactions are attractions between molecules that are close together as a result of these charges .

1)

2)

3)

Chemical Reactions Make and
Break Chemical Bonds

Water

The Universal Solvent

Solution - liquid that is a homogenous mixture of substances

Solvent - dissolving agent

Solute - substance that is dissolved

Water is a versatile solvent due to its polarity, which forms H bonds easily

Heat and Temperature

Kinetic Energy - energy of motion

Heat - total amount of kinetic energy used due to molecular motion

Temperature - measures the intensity of heat due to average kinetic energy

Calorie - amount of heat required to raise the temperature of 1g or water by 1°C

Specific heat - heat absorbed or lost for 1g of a substance to change temperature by 1°C