CHEMISTRY AND LIVING THINGS Why is chemistry important in

biology?• Organisms are made of macro-

________.• Macromolecules are made of

smaller _______, made of atoms.

Atoms

The Smallest piece of an ________. ________ is made up of atoms

Subatomic Particle

Charge Location

Proton (+) Nucleus

Neutron No charge Nucleus

Electron (-) Outside Nucleus

Bohr Model: What makes a nickel different from a piece of gold?

VALENCE ELECTRONS:THE OUTER SHELL OF ELECTRONS DETERMINES AN ATOM’S PROPERTIES.

Elements & Periodic Table

Element= A substance made up of __ type of atom 92 natural elements more than 113 total Arranged in the Periodic Table based on atomic number

and common properties

ISOTOPES Isotopes= Atoms of the same element

that differ in the number of neutrons they contain are known as isotopes

The sum of the protons and neutrons in the nucleus of an atom is called its mass number.

Atomic Number

Atomic Mass

C6

12.01

# of Protons

P + N

* The number of protons equals the number of electrons!

P+

6

N 6

E- 6

ISOTOPES

Isotopes are identified by their mass numbers.

For example, carbon has three isotopes—carbon-12, carbon-13, and carbon-14. Each isotope has a different number of neutrons.

ISOTOPES Because they have

the same number of electrons, all isotopes of an element have the same chemical properties.

RADIOACTIVITY Radioactive Isotopes

Some isotopes are radioactive, meaning that their nuclei are unstable and break down at a constant rate over time.

Although the radiation these isotopes give off can be dangerous, they have important scientific and practical uses.

RADIOACTIVITY

• Radioactive isotopes can be used: to determine the ages of rocks and fossils. to treat cancer. to kill bacteria that cause food to spoil. as labels or “tracers” to follow the

movement of substances within an organism.

Chemical Compounds

The same way atoms combine to form elements, elements combine to form compounds.

Compounds have different properties than the elements that make them up.

Water (H20)

Ahh… Nirvana

All atoms want to have a full outer shell 1st level = 2 electrons All other shells = 8 electrons As you move to the right of the periodic table,

the elements are getting closer to a full outer shell.

How do atoms combine?

Covalent Bonds• Sharing of electrons

• Ionic Bonds•Giving/Taking of electrons• Ions – charged atoms

IONIC BONDS An atom that loses electrons has a positive

charge.  An atom that gains electrons has a negative

charge. These positively and negatively charged

atoms are known as ions.

COVALENT BONDS= SHARING

Terms to know

Atom Proton, Neutron, Electron

Element Atomic Mass Atomic Number Compound Covalent Bond Ionic Bond