Chemistry of Life

•Composition of Matter

anything that occupies space and has massMatter

is the quantity of matter an object hasMass

Mass vs. Weight•Weight is determined by the force of gravity acting on a mass

•Example: The same mass would have less weight on the moon than on the Earth

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90% of the mass of all living things are

composed of just four elements:

Carbon Hydrogen Oxygen Nitrogen

Elements are substances that cannot be broken down chemically into simpler kinds of matter

Elements and Atoms

Over 100 elements exist.

Fewer than 30 are important for

life

•chemical symbol- consists of 1,2,or 3 letters•derived from first letter or other letters in the name •Ex: Chlorine-Cl

•Most other names are derived from Latin names

ELEMENTS – organized in Periodic Table

Consist of 3 SUBATOMIC PARTICLES

•ATOMS – simplest particles of an element that retains all the properties of that element

Protons Neutrons Electrons

nInside Nucleus

Outside Nucleus

NUCLEUS - the central part of an atom and makes up the bulk of the mass of an atom

# electrons = # protons in a NEUTRAL ATOM

high energy –fast orbit very little mass located in orbitals or energy

levels Electrons in outer orbitals have

more energy 1st energy level can only hold 2

electrons 2nd energy level can hold up to

8 electrons

ELECTRONS- are negatively charged particles found orbiting the nucleus of an atom

Isotopes-atoms of the same element that have a different number of neutrons

Compounds - made up of atoms of two or more elements in fixed proportions

• shows the kinds and proportions of atoms of each element that forms a particular compound

Chemical Formula

H2O 2 Hydrogen Atoms

1 Oxygen Atom

o Elements will combine to form molecules or compounds if their outer energy level or orbital is NOT FILLED.

o An atom is chemically stable when its highest energy level is filled with the maximum number of electrons. These elements are called noble or inert

elements (gases) and do not react with other elements under normal conditions. (Ex: Helium, Neon)

So,when does bonding occur?

CHEMICAL BONDS – attractive forces that hold atoms together

Ionic Covalent

Hydrogen

Covalent Bonding - form when two atoms share one or more pairs of electrons

electrons in an atom’s outermost energy level = valence electrons

When outer shell is filled – atom is stable

Hydrogen has ______electron so it needs __________more to fill its first energy level to achieve stability

• Atoms gain or lose electrons to achieve stability• they become either positively charged or negatively charged

• NaCl is table salt and forms from a Na+ ion bonding with a Cl- ion

• Ionic Bonds- form from the attractive force between oppositely charged ions (charged particle)