Chapter 2 Flashcards
the smallest unit of an element is the ___
atom
the nucleus of the atom contains ___ and ___
protons; neutrons
what are the four elements that make up living organisms?
carbon, nitrogen, oxygen, hydrogen
the atomic number is the number of ___ in the atom
protons
atomic mass equals ___
protons + neutrons
isotopes are atoms of the same element that differ in the number of ___
neutrons
an isotope that gives off energy, sometimes making the element unstable, is called a ___
radioisotope (radioactive isotope)
radioisotopes can be used in medicine as ___
tracers in the body
the energy emitted by ___ can be strong enough to kill harmful cells
radiation
atoms interact with surrounding atoms through their ___
electrons
like charges ___
repel
opposite charges ___
attract
slots of first three electron orbitals:
2, 8, 8
the further away from the nucleus, the more ___ electrons get
potential energy
when orbitals are filled, the atom is ___
stable
atoms that have bonded together make up ___
molecules
the three types of bonds in biochemical reactions are:
ionic, covalent, hydrogen
atoms are initially ___ charged
neutrally
when an atom gains an electron, it becomes ___ charged
negatively
when an atom loses an electron, it becomes ___ charged
positively
atoms become ___ when they gain or lose electrons
ions
a cation is a ___ charged ion
positively
an anion is a ___ charged ion
negatively
type of bond where one atom gains an electron (becoming negative) and one atom loses an electron (becoming positive)
ionic
type of bond where atoms (similar electronegativity) share one or more pairs of electrons
covalent *usually stronger than ionic bonds
in nonpolar covalent bonds, electrons are shared ___
equally
in polar covalent bonds, electrons are shared ___
unequally
type of bond where positive end of one polar covalent molecule is attracted to the negative end of another covalent molecule
hydrogen *do not form molecules. only hold molecules together.
is water electronegative?
yes
___ substances are polar
hydrophilic
___ substances are nonpolar
hydrophobic
pH is the measure of free ___ in a solution
hydrogen
acids ___ hydrogen when dissolved in water
donate
bases ___ hydrogen when dissolved in water
accept
___ keep pH toward neutral
buffers
elements consist of only atoms with the same ___
atomic number
