NOTES: 2.1

The Nature of Matter(Basic ChemistryBasic ChemistryBasic ChemistryBasic Chemistry Review)Review)Review)Review)

Molecular Level (DNA)

Atomic Level (Phosphorus)

Vocabulary

• Atom

• Isotope

• Compound

• Covalent Bond

• Acid

• Base

• Covalent Bond

• Ionic Bond

• Molecule

• Mixture

• Solution

ELEMENT: substance that cannot be broken down into other substances by chemical reactions

Nitrogen vs. No Nitrogen

reactions

Enlarged thyroid gland

caused by iodine deficiency.

• Each element is represented by a one or two-letter abbreviation

– Examples

• C = carbon

• Na = sodium

• Pb = lead• Pb = lead

• Trace Elements

– Present in living organisms but found in

very small amountsvery small amounts

• Examples: Iron, Iodine, Manganese

COMPOUND: pure

substance composed of 2 or

more elements combined in

a fixed ratio

• examples: NaCl, H2O,

CO , C H OCO2, C6H12O6

• have unique properties

beyond those of the

combined elements

ATOM: smallest unit of matter that retains the physical and chemical properties of its element

• three subatomic particles:

Particle Charge Location Mass

PROTON + nucleus1.009 amu

NEUTRON 0 nucleus 1.007 amu

ELECTRON - electron

cloud1/2000 amu

ELECTRON ENERGY LEVELS

• Region where electrons travel around nucleus

• Each level has a limited capacity to hold electrons

• First energy level is the smallest and can only hold 2 electrons

– 2nd energy level = 8 electrons

– 3rd energy level = 18 electrons

ATOMIC NUMBER: # of protons in an atom of an element

-all atoms of an element have the same atomic #

-written as a subscript next to the element’s

symbol

-in a neutral atom, # protons = # electrons-in a neutral atom, # protons = # electrons

MASS NUMBER:

# of protons + # of neutrons

written as a superscript next to element’s �written as a superscript next to element’s

symbol

� # of neutrons can vary in an element,

but proton # is constant

Isotopes: atoms of an element that have

different # of neutrons

-in nature, elements occur as mixtures of isotopes

-some are radioactive: unstable -some are radioactive: unstable isotope where nucleus decays emitting sub-atomic particles and/or energy as radioactivity causing one element to transform into another element

• Some ways radioactive isotopes are useful to scientists:– Ages rocks or fossils

– Treats cancer

– Kills bacteria in food

– Used as a “tracer” in human body or as a way to label something in the body

Half-life: the time it takes for 50% of radioactive atoms in a sample to decay

Energy Levels of Electrons

• Electrons are the only subatomic particle involved in chemical reactions because they occupy because they occupy energy levels surrounding the nucleus

*Covalent bond: strong chemical bond between atoms formed by sharing a pair of valence electrons

*Ionic bond: bond formed by the attraction of a positive ion to a negative ion

-anion: negatively charged ion; has gained 1 or more electronsgained 1 or more electrons

-cation: positively charged ion; has lost 1 or more electrons

Chemical Reactions

• In a chemical reaction, bonds between

atoms are formed or broken, causing

substances to combine and recombine

as different molecules;

• All of the chemical reactions that occur

within an organism are referred to as

that organism’s METABOLISM.

Chemical Equations:

• REACTANTS: the substance(s) at the beginning of a reaction; shown on the left side of the equation;

• PRODUCTS: the substance(s) at the end of • PRODUCTS: the substance(s) at the end of a reaction; shown on the right side of the equation.

• Example:

H2 + O2 � 2H2O

Mixtures and Solutions:

• MIXTURE: a combination of 2 or

more pure substances in which the

individual components retain their individual components retain their

own properties

• Examples: sand & sugar

water & salt

SOLUTIONS:

• SOLUTION: a mixture in which the solute(s) are evenly distributed in the solvent

• Example: salt in water

**Solutions are important to living things!!

ACIDS & BASES

• In living things, chemical

reactions depend on the pH of

the environment

• pH = a measure of how acidic • pH = a measure of how acidic

or basic a solution is

The pH scale:

• ACID: a solution with a pH below 7

• BASE: a solution with a pH above 7