Biology Ch.2 Flashcards
Electron shells
first shell (2 electrons), second and third max 8 electrons
Valence electrons
outer shell electron –> interacts with other atoms
If the valence orbital is full
the atom is inert, meaning unlikely to react
3 types of chemical bonds
covalent bonds
ionic bonds
hydrogen bonds
covalent bonds
share valence electrons, the valence shells overlap, each electron completing the valence shell for the other
polar covalent bond
electronegetivities in a compound are unequal –> resulting in a partial differences on different sides of the moelcule
Nonpolar covalent bond
the electronegativities of the atoms are equal
electronegativitty
the attraction of a given atom for the electrons of a covalent bond
Ionic bonds
former by electrical attractions between opposite charges and ions
anion
negatively charged (gain e)
cation
positively charged (loses e)
Hydrogen bond
non-covalent (does not share electrons) between hydrogen and an electronegative atom
bond strength order
covalent (strongest), followed by ionic, then hydrogens
what can affect molecule shape
electronegativities and bonds
cohesion
water molecules stick together (many hydrogen bonds, responsible for surface tension)
adhesion
hydrogen bonds between water molecules and other molecules
thermal energy
kinetic energy associated with random movements of atoms and molecules to change temp 1C
specific heat
amount of heat that must be absorbed or lost
whats special about water and its absorption/loss of energy
water has a very high specific heat meaning it takes a lot of energy to change the temp of water, but it manages to then hang onto that energy. also takes a lot of energy for water to evaporate –> sweat!
Solution
liquid homogenous mixture of two or more substances
solvent
substance that solute dissolves in
solute
substance that dissolves
water is…
a good solvent! it dissolves polar substances
hydrophilic
water loving, polar substances dissolve easily
Hydrophobic
water hating, things that do not dissolve in water = non-polar molecules
Acid
substance that increases H+ concentration
Base
substance that releases OH-, REDUCES H+ concentration
as pH number gets smaller, the number of hydrogens…
increases
subatomic particles
protones, neutrons, electrons
atomic number
of protons
mass number
of protons + # of neutrons
Isotopes
same element, different number of neutrons
buffers
substances that minimize changes in concentration of H+ and OH- in a solution by donating or accepting H+
