Element

a substance that cannot be broken down into other substances

4 Most Abundant Elements in Humans

1. Oxygen

2. Carbon

3. Hydrogen

4. Nirtogen

Atom

Smallest particles that retain the properties of an element

Proton

A subatomic particle that has a positive charge.  Located in the nucleus of an atom.

Neutron

A subatomic particle that does not carry a charge.  Located in the nucleus

Electron

A subatomic particle that has a negative charge.  Located in shells around the nucleus.z

An atom has an equal number of

protons and electrons

Atomic Number

Number of protonss in an atom

Mass Number

The number of protons and neutrons

Isotope

All atoms of an element have the same number of protons, but don't have the same number of neutrons

Radioisotope

An isotope that has an unstable nucleus and stabilizes itself by emitting energy and particles

Radioactive Decay

transforms a radioisotope into an atom of a different element at a known rate

Tracer

any substance with a radioisotope attached to it

Orbitals

the space around the atomic nucleus where electrons are found

The first orbital (shell) can hold ____ electrons

2

After the first orbital (shell) all others can hold _____ electrons

8

The farther an electron is from the nucleus the _______ its energy

greater

Ionic Bond

•  a bond between two atoms that has either lost or gained one or more electrons
• a strong bond

Covalent Bond

• sharing of a pair of electrons between two atoms
• are polar or non polar

Nonpolar

• no difference in charge between two ends of the bond
• Ex: H-H

Polar

• atoms do not exert the same pull on shared electrons
• one end is - the other is +
• Ex: H₂O

Single Covalent Bond

• share on electron
• Ex: H-H

Double Covalent Bond

• share two electrons
• Ex: O=O

Triple Covalent Bond

• share three electrons
• Ex: NΞN

Hydrogen Bond

• a weak attraction between an electrogegative atom and a neighboring hydrogen atom
• Ex: H₂O

Hydrophilic Substance

• a polar substance that dissolves easily in water
• Ex: sugar

Hydrophobic Substance

• a nonpolar substance that strongly resists being dissolved in water
• Ex: oil

Temperature

a measure of the molecular motion of a given substance

Evaporation

heat energy converts liquid water to a gas

Solute

any substance dissolved in a solution

Solvent

any fluid in which substances are dissolved

Cohesion

• attraction between like molecules
• resist rupturing when placed under tension

Surface Tension

hydrogen bonding exert a continual inward pulling on waster molecules at or near the surface

Acids

any substance that donates H+ to other solutes or to water molecules

Base

any substance that accepts H+ from other solutes or from water molecules and OH- forms