The Chemical Context of Life Flashcards
element
An ELEMENT is a substance that can not be broken down into other substances by chemical reactions.
matter
anything that takes up space and has mass
compound
A COMPOUND is a substance of two or more different elements combined in a fixed ratio.
essential elements
96% of living matter : carbon (C), oxygen (O), hydrogen (H), nitrogen (N) phosphorus (P), sulfur (S), calcium (Ca), potassium (K) and a few other elements make the remaining 4% of living matter
trace elements
TRACE ELEMENTS are those required by an organism in only minute qunatities. eg.: iron
atom
An ATOM is the smallest unit of matter that still retains the properties of an element.
mass of atoms, subatomic particles, molecules: UNIT
daltons, atomic mass unit, amu
John Dalton
British scientist, 1800, atomic theory
atomic number
number of protons eg.: 2He indicates that helium has 2 protons
mass number
sum of protons plus neutrons in the nucleus of an atom, eg. 23/11 Na -> Na has 11 protons, 12 neutrons
isotopes
Atoms of the same element have the same number of protons, but a different number of neutrons
radioactive isotope
A radioactive isotope is one in which the nucleus decays spontaneously, giving off particles and energy.
energy
capacity to cause change
ion
charged atom or molecule
orbital
the threedimensional space where an electrone is found 90% of the time; no more than 2 electrons can occupy a single orbital
strongest chemicals bonds
covalent bonds and ionic bond
covalent bond (Elektronenpaarbindung)
A covalent bond is sharing of a pair of valence electronsby two atoms. eg. hydrogenbond
molecule
two or more atoms held together by covalent bonds constitute a molecule
valence
the atoms bonding capacity
electronegativity
attraction of a particular kind of atom for the electrons of a covalent bond
nonpolar covalent bond
a bond, in which electrons are shared equally
polar covalent bond
one atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally
cation
positive ion
anion
negative ion
ionic bond
Because of their opposite charges, cations and anions attract each other. This attraction is called ionic bond. Compounds formed by ionic bonds are called ionic compounds or salts.
Van der Waals Kräfte
schwache Kräfte zwischen Molekülen; sind umso stärker, je länger die Molelüle; erhöhen die Siedetemperatur; enstehen aufgrund von Ladeschwerpunkten zwischen den Molekülen, da Elektronen sich nicht gleichmäßig um den Atomkern bewegen
