Unit 1 Chemistry of Life: Atoms and Molecules

Elements Required for Life Approx 25 elements C, O, H and N  96% of living matter P, S, Ca and K  4% of an organism’s weight Trace elements  Needed in minute quantities  Ex. Fe, I, Mg

Matter Anything that takes up space and has mass Solid, liquid, gas Elements cannot be broken down further  Fe, Rb, Fr Compounds consist of two or more elements  NaCl, H2O, H2CO3

Periodic Table of Elements Groups Periods Atomic number Atomic mass Metals/Non metals Families Trends

Chemical Families Alkali metals Alkaline earth metals Metalloids Halogens Noble gases Transition metals Actinide/Lanthanide Series

Atomic Structure Atom-Smallest unit of matter  Subatomic particles-Parts of atom  Neutron/proton  mass=1.7X g  (1 Da or amu)   Mass of electron is  negligible (1/2000)

Atomic Number and Weight All atoms of an element have same number of protons; this is atomic number 2 He All atoms have a balanced charge, therefore:  Atomic number=Protons=Electrons Mass number=Protons + neutrons (round mass #) Mass number – atomic number (protons)=Neutrons All of atom’s mass is in nucleus; this is atomic weight

Isotopes Atoms of a given element that contain different number of neutrons, but same protons All natural elements exist as a mixture of all its isotopes Some are radioactive isotopes which have a spontaneously decaying nucleus  Radiology

Energy Levels Each electron shell contains a certain amount of energy (n) As you move up the energy increases e- moving up absorbs energy e- moving down loses energy, releasing heat # e- in each level=2(n) 2 For atomic structure:  Place neutrons and protons in nucleus  Arrange e- using 2n 2

Valency The number of electrons that orbit the outermost energy level This is equivalent to the charge

Chemical Bonding All bonding occurs in the outer shell of atoms (sharing of valance e-) Types of bonds:  Covalent Bonds-Sharing of a pair of valence electrons by two atoms.  Non polar covalent: e- are shared equally (methane)  Polar covalent: Unequal sharing of e-. One tends to pull harder (HCl or water)  Ionic Bonds-Transfer of e- from the negative ion to the positive ion.  Ion-Element that loses or gains an electron  Hydrogen Bonds-Hydrogen atoms bonded to electronegative atoms  Van Der Waals Interactions-All atoms and molecules when close to each other tend to “stick” to one another. Occurs due to natural gravitational forces of atoms

Non-Polar