Bio Chapter 4

Atom

Basic unit of matter

Nucleus

Central portion of atom

Protons

Subatomic particle with a positive charge

Neutrons

Substance particle with no charge

Element

A pure substance that cannot be broken down into another substance - made with the same kind of atom

Essential Biological Elements

Make up all living things

Atomic #

Number of protons or electrons in the atom

Atomic mass

Average sum of the protons and neutrons

Isotopes

Different form of the same element - same # of protons but different # of neutrons

Good isotopes

Medical uses, determines age of fossils

Bad isotopes

Damages cells if exposed for a long time

Compound

Substance containing 2 or more elements

Reactants/inputs

starting materials

Products/outputs

end materials

Chemical Formula

tells the # and type of atoms in a substance

Structural Formula

Shows how the atoms are bonded together

Chemical Bonding

Based upon the number of valence electron of a atom

Valence Electrons

The electrons in the outer most energy level

Polar Molecule

Oxygen is larger and pulls all e- to it. Takes on a net negative charge. Hydrogen is left with a positive charge

Hydrogen Bonds

Weak attraction between the H of one H20 to to oxygen

Cohesion

Attraction between 2 water molecules

Surface Tension

Water clinging together to form a strong layer

Adhesion

Attraction between water and OTHER substances

Temperature Moderation

Hydrogen bonds cause water to resist temp change

Low Density of Ice

Hydrogen forms bonds that keep molecules spaced apart

Solubility

Ability to dissolve other substances easily

pH Scale

Measurement of amount of H+ or OH- ions in a solution

Acids

Have a lot of H+ ions - pH below 7

Bases

Have a lot OH- ions - pH above 7

Buffer

Chemicals that resist change in pH