NOTES: 2.1 The Nature of Matter (Chemistry Review) Atomic Level (Phosphorus) Molecular Level (DNA)

VOCABULARY ● Atom ● Isotope ● Compound ● Covalent Bond ● Ionic Bond ● Molecule ● Mixture ● Solution ● Acid ● Base

Life is made up of MATTER! ● MATTER can be defined as anything that has mass and takes up space…this includes individual atoms!! ● just as buildings are made from bricks, steel, glass, and wood, LIVING THINGS are made from CHEMICAL COMPOUNDS.

The Chemistry of Life… ● when you breathe, eat, or drink, your body uses the substances in air, food, and water to carry out chemical reactions that keep you alive… ● just as an architect first must understand the building materials, a BIOLOGIST must first understand the compounds that make up living things!

ATOM: smallest unit of matter that retains the physical and chemical properties of its element ● three subatomic particles: Particle ChargeLocationMass PROTON + nucleus amu NEUTRON 0 nucleus amu ELECTRON - electron cloud amu

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

MASS NUMBER: # of protons + # of neutrons ● 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 isotope where nucleus decays emitting sub- atomic particles and/or energy as radioactivity causing one element to transform into another element

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

● 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

ELEMENT: a pure substance that consists entirely of one type of atom; a substance that cannot be broken down into other substances by chemical reactions Enlarged thyroid gland caused by iodine deficiency. Nitrogen vs. No Nitrogen

COMPOUND: pure substance composed of 2 or more elements combined in a fixed ratio examples: NaCl, H 2 O, CO 2, C 6 H 12 O 6 cmpds. have unique properties beyond those of the combined elements

Chemical Compounds ● a MOLECULE is the smallest unit of most compounds! ● EXAMPLE: 1 molecule of water, H 2 O, is the smallest unit of water possible; it consists of 2 hydrogen atoms & 1 oxygen atom bonded together.

Energy Levels of Electrons ● Electrons are the only subatomic particle involved in chemical reactions because they occupy energy levels surrounding the nucleus

*IONIC BOND: bond formed by the attraction of a positive ion to a negative ion -anion: negatively charged ion; has gained 1 or more electrons -cation: positively charged ion; has lost 1 or more electrons

*COVALENT BOND: strong chemical bond between atoms formed by sharing a pair of valence 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 a reaction; shown on the right side of the equation. Example: 2H 2 +O 2  2H 2 O