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39 Cards in this Set

  • Front
  • Back
cannot be broken down into similar substance by chem reactions - 92 naturally occurring
2 or more element in fixed ratio
example of emergent property in elements
change chars when combined into compounds
elements necessary for life
most common elements
96 percent of human life=
carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)—make up 96% of living matter.
Most of the remaining 4% of an organism’s weight consists of phosphorus (P), sulfur (S), calcium (Ca), and potassium (K).
Trace elements are required by an organism but only in minute quantities
smallest unit of matter with the properties of the element
what keeps the electrons around the nucleus?
attraction of negative to positive charge
unit used to measure mass for atoms and subatom particles
-prot and neut each about 1 dalton
atomic number
number of protons in nuclei... all atoms of element have the same number
- subscript in front of symbol
mass number
sum of protons and neutrons
- used to calculate atomic weight (atomic weight in daltons)
- superscript
same element different # of neutrons
radioactive isotopes
unstable isotopes, decay spontaneously emitting particles and energy
ex 14c, when it decays a neutron converts to a proton and an electron, turning into 14n a different element
- many applications in biological research such as fossil dating. tracing atoms and pet scans
- if a substance with a known quantaty of radioactive isotope is injected into the blood its rate of excretion in urine can be measured
- energy emitted is hazardous to life
- destroy molecules in living cells
structure of an atom
mostly empty space, small ucleus and electrons
subatomic particles in chem reactions
electron config effects chemical behavior of the atom... nuclei do not come close enough to contact
ability to do work
energy in electrons
potential energy because of position relative to nucleus, farther away= more pot energy
- changes in pot energy only occur in fixed amounts (must absorb or release energy that matches the diff in pot energy between levels)
elements ion the periodic table
same rows fill the same shells with electrons. moving left to right each element adds one electron
electrons in outer shell
valence electrons
same number of valence electrons=
similar chemical behaviors
electron orbitals
-complex 3d space where electron is found 90% of the time
- can hold a max of 2 electrons
- first shell= 1s orbital
- second shell= 2s and 3 2p (dumbell shaped)
electron positioning
occupy separate orbitals within the valence shell until forced to share
unpaired electrons make the atom reactive and are involved in chem reactions
chemical bonds
atoms are attracted close together after chem reactions
- covalent and ionic are the strongest
covalent bond
sharing of a pair of valence electrons-- both atoms count both electrons
2 or more atoms held together by covalent bonds
structural formula = H-H
molecular formula= h2
atom's valence
its bonding capacity (number of unpaired electrons)
attraction of an atom for the shared electrons of a covalent bond
- strong electroneg atoms pull electrons towards themselves
nonpolar/polar covanlent bond
nonpolar= shared equally (similar or same electronegativities) (CH4)

polar- differ in electroneg (h20) partial negative charge near the strong electroneg atom and partial positive near the weaker
ionic bond
2 atoms are so unequal in attraction for valence electrons that one strips electron away
- strength depends on environment
after ionic bond atoms are not neutral
cations- positive
anions- negative
---- atoms in ionic bond can have charges that are not caused by transfered with each other

can also be charged molecules
ionic compunds
formed by ionic bonds, salts, like nacl
weak bonds
ionic bonds in water, hydrogen bonds, and van der wals interactions play important roles in chemistry of life
hydrogen bonds
hydrogen atom covalently bonded to strongly electroneg atom is attracted to another strongly electroneg atom
-- occur because of the partial neg and pos charges
van der waals interactions
temproary regions of partial neg and positive charge because electrons are always in motion. when they accumulate by chance in one area it chreates changing reagions of partial negative and pos charges and molecules in close proximity can be attracted
shape of a molecule
determines the function
- determined by the positions of electron orbitals shared by the atoms involved in the bond
- moleccular shape is how biological molecules recognize and interact with one another
covalent bonds and molecule shape
orbitals in valence shell rearrange
for electrons in s and p, bond makes 4 new orbitals in tetrahedrals shape
example of molecular shape dictating function
signal molecules from a transmitting cell bind to receptor molecules from a receiving cell
te temporary attachment of the receptor and signal molecule stimulates activity in the receptor cell
molecules with similar shapes have same biological effects ie heroin shaped like endorphins
starting molecules in chem reaction? final molecules?
reactants and products
carbon dioxide and water --> sugar and oxygyn
powered by sunlight
6c02+6h20= c6h1206+6O2
reversible reactions
when reactant concentrations are high they collide requently to make products and as the products build up they collide to reform reactants.
eventually the rate of formation of products is the same as the rate of breakdown== chemical equilibrium
concentrations stabilized at a particular ratio.