The Chemistry

of Life

Atoms and Their Interactions

Atoms and Their Interactions

Objectives Relate the structure of an atom to the

identity of elements Relate the formation of covalent and ionic

chemical bonds to the stability of atoms Reexamine mixtures and solutions Define acids and bases and relate their

importance to biological systems

Elements Everything is made of elements

An element cannot be broken down into a simpler chemical substance

Only 25 are essential to living organisms Carbon, hydrogen, oxygen and nitrogen make

up more than 96% of the mass of the human body

Each element is identified by a one or two letter abbreviation called a symbol

Atoms: The Building Blocks of

Elements Atoms are the smallest part of an element

that has the characteristics of that element

Atoms are the basic building blocks of all matter

The way atoms are put together affects the properties of the chemical they make up

Sugar vs. Coal and Water

Glucose

Carbon, Hydrogen and

Oxygen

C6H12O6

Coal and Water

Carbon, Hydrogen and Oxygen

H2O (water)

Carbon and Hydrogen (coal)

Sugar vs. Coal and Water

Glucose Coal and Water

The Structure of an Atom

Isotopes of an Element

Atoms of the same element always have the same number of protons

Atoms of the same element with different numbers of neutrons are called isotopes

Compounds and Bonding

A substance composed of 2 or more different elements that are chemically combined is a compound

Atoms combine with other atoms when the resulting compound is more stable (this happens most of the time)

Stability = full energy level

How do atoms fill their energy levels? Share Give / take

Covalent Bond

Covalent Bond When two atoms share electrons, the force

that holds them together is called a covalent bond

A group of atoms held together by covalent bonds is called a molecule

H2O 2 Hydrogen atoms 1 Oxygen Atom

Ionic Bond

Ionic Bond An atom (or group of atoms) that gains or

loses electrons is electrically charged

An atom (or group of atoms) that is charged is called an ion

The attractive force between two ions of opposite charge is called an ionic bond

Chemical Reactions

Occur when bonds are formed or broken, causing substances to recombine into different substances

All chemical reactions that occur within an organism are referred to as that organisms metabolism

These reactions breakdown and build molecules important for the functioning of organisms

Cl2 + NaBr NaCl + Br2

How do we balance this equation?

Mixtures and Solutions

A mixture is a combination of substances in which the individual components retain their own properties

A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent)

Solutions are important in living things

In organisms, many vital substances (such as sugar and mineral ions) are dissolved in water

The more solute dissolved in a given amount of solvent, the greater the concentration

Organisms must keep concentrations of dissolved substances within a specific, narrow range

Acids and Bases Organisms must also keep the amount of

bases and acids within a narrow range

We measure this with the pH scale

Acids An acid is any substance that forms (H+)

ions in water

Bases A base is any substance that forms (OH-)

ions in water