Chapter Two Flashcards
atom?
the smallest piece of an element that retains the characteristics of that element
element?
pure substance containing only one type of atom, cannot be broken down by chemical means
molecule?
made up of atoms and is a stable association of atoms, can be composed of one or more elements
compound?
made up of molecules of at least two different elements, NaCl is compound
proton’s charge, mass, and location?
proton has a positive charge, a mass of 1 (amu) located inside the nucleus
neutron’s charge, mass, location?
No charge, mass of 1 amu and it is located inside the nucleus
Electron’s charge, location, and mass?
negative charge located in orbitals 90% of the time and the mass is 0 essentially
atomic number?
the number of protons of the atoms, this identifies the element
atomic weight?
is the average mass of all the isotopes of a particular element
molecular weight?
the sum of all the atomic weights of all atoms in a molecule
mass number?
the number of protons and neutrons in a atoms nucleus
isotope?
an element with the same number of protons but different number of neutrons, so same element may have different mass number
orbital?
region where an electron is located at least 90% of the time, can be occupied by a maximum of 2 electrons
electron shell?
is the energy level
in the shell, orbitals are filled in a specific sequence
1st shell holds 2 electrons 1 orbital
2nd shell holds 8 electrons 4 orbitals
valence shell?
the outermost shell, which determines how the atoms will behave
when is an atom reactive / unstable?
when there are unpaired electrons in orbitals in the outer valence shell
when is an atom stable / non-reactive?
when the valence shell is full
covalent bonds?
when atoms share one or more pairs of electrons so that the valence shell is filled
they are very strong bonds - lots of energy to break them
can have single (one pair), double (two pairs) or triple (three pairs)
50-110 bond energy
polar covalent?
when one atom has a greater electronegativity so the electrons shared in the bonds are more attracted to to that atom’s nucleus.
non polar covalent?
when atoms have same electronegativity so electrons shared in the bond are shared equally.
ionic bonds?
when one atom is much more electronegative, a complete transfer of electrons occurs
the result is two ions, one positively charged and one negatively charged
Ionic bonds are bonds formed from the electrical attractions of positive and negative ions
3-7 bond energy
hydrogen bond?
is an attraction between the positive side and the negative side of another molecule (H2O) is a good example
3-7 bond energy
van der Waals
occurs when adjacent atoms come close enough that the outer electron clouds just barely touch.
bond energy is 1
redox reaction (oxidation-reduction) reaction?
when electrons are transferred between two molecules
if a molecule is reduced it gains a negative charge, or an electron (acceptor/agent that oxidizes)
if a molecule is oxidized it gains a positive charge by losing an electron (electron donor/agent that reduces)
what bond is between one water molecule?
(polar) covalent because oxygen is much more electronegative than hydrogen
what bond is between two water molecules?
hydrogen bonds form between water molecules when the polar ends of each other (negative oxygen) (positive hydrogen) are attracted to each other
cohesion?
the tendency of water molecules to stick together because of hydrogen bonds
this results in high surface tension, and helps water move up plants
adhesion?
is the attraction of water molecules to other molecule of a different type
is water more dense as a liquid or as a solid?
water is more dense as a liquid because when water freezes the space between molecules increase and they move very slowly vs. when water is a liquid it moves freely and molecules to bond to each other easier
acid?
an acid a molecule that releases hydrogen ions H+
strong acid is when all acid molecules dissociate completely (all release their H+)
weak acid is when not all of the molecules dissociate, so it can be reversible sometimes
base?
molecules that accept H+
strong acids take all H+ ions
weak acids take some H+ ions
Functional group of biological acids
COOH to COO + H+
pH scale is based on what?
is based on the H+ concentration in moles/ L
Acid pH?
Acids have high H+ concentration so they are zero on the scale
10^-1 = 1 on the scale
base pH?
bases have low H+ concentration
10^-14 = 14 on the scale
Buffer?
is a weak acid and its corresponding base
its helps maintain a constant pH
if a strong acid is added to the buffer solution not all the H+ in the solution will remain, some will be eaten up by the weak base.
as we discussed earlier, sometimes weak bases / weak acids can be reversed to keep everything balanced
law of mass action?
addition of a reactant (acid) on one side of a reversible system drives the system in the direction that uses up that compound
