Chemistry of Life

Composition of Matter anything that occupies space and has mass Matter is the quantity of matter an object has Mass 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

. 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 ATOMS ProtonsNeutronsElectrons n Inside 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  1 st energy level can only hold 2 electrons  2 nd 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 H2OH2O 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 IonicCovalent 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)