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BIOL 1345 1-2 Chemical Foundations

Terms in this set (51)

matter
anything that has mass and occupies space
atom
smallest unit of matter that retains all the chemical properties of an element
element
a pure substance made up of only one type of atom; cannot be broken down to other substances by chemical reactions
molecule
two or more atoms chemically bonded together
compound
substance consisting of two or more elements in a fixed ratio; has characteristics different from those of its elements
atomic number
number of protons in its nucleus
mass number
sum of protons and neutrons in the nucleus
atomic mass
mass of total atom; can be approximated by the mass number
What are atoms composed of?
protons, neutrons, electrons
protons
positively charged subatomic particles that reside in the nucleus of an atom; have significant mass
number of protons
give the unique, defining property of atoms of a particular element
neutrons
uncharged subatomic particles that reside in the nucleus of an atom; have significant mass
electrons
negatively charged subatomic particles that reside outside of the nucleus of an atom; has negligent mass
periodic table
organizational chart of elements indicating the atomic number and atomic mass of each elements; provides key information about the properties of the elements
isotope
one or more forms of an element that have a different number of neutrons; many are stable
radioisotope
isotope that emits radiation composed of subatomic particles to form more stable elements; break down over time
How many elements are essential to life?
25
How many elements are naturally occurring?
92
What about the other elements that are not naturally occurring?
those are either synthesized in laboratories or highly unstable
trace element
elements required by an organism in minute quantities
ion
atom or chemical group that does not contain an equal number of protons and electrons
electron shells
average distance of electron from the nucleus and also state of potential energy itcorrelates with
potential energy
energy that matter has because of its location or structure
energy
the capacity to cause change
electron orbitals
how electrons are spatially distributed surrounding the nucleus; usually a three-dimensional space
chemical reactions
the making and breaking of chemical bonds; all are reversible
chemically reactive
atoms in which the outermost energy level is not completely filled with electrons
chemically inert
atoms in which the outermost energy level is completely filled with electrons
noble gases
group of elements that are chemically inert and stable because of their occupied valence shells, which keeps them from readily donating, accepting, or sharing electrons
Why do atoms form molecules?
to achieve a stable number of electrons
emergent properties
new properties that arise with each step upward in the hierarchy of life, owing to the arrangements and interactions of parts as complexity increases
anion
negatively charged ion that is formed by gaining one or more electrons
cation
positively charged ion that is formed by losing one or more electrons
negative charge of an ion
indicates the number of electrons the ion has gained
positive charge of an ion
indicates the number of electrons the ion has lost
polar bonds
when electrons are more attracted to the nucleus of one atom than the other, resulting in partial charges
nonpolar bonds
when atoms share the bond of electrons equally
covalent bond
type of strong bond between two of the same or different elements; forms when atoms share a pair of valence electrons; can be single or double
ionic bond
electrical attractions between atoms that gain or lose valence electrons completely; it forms between ions with opposite charges; strong, but not as strong as covalent
salts
compounds formed my ionic bonds
hydrogen bond
weak bond between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules; occur when there is unequal electron sharing in two different covalent bonds; individually weak, but are essential for maintaining the shape of many biological molecules when they bond collectively
van der waals forces
very weak interaction between moleculesdue to temporary charges attracting atoms that are very close together over very short distances; temporary zones positive and negative charge make the molecule polar; stabilizes molecules when they bond collectively
Which elements share electrons unequally with hydrogen and create polar molecules?
oxygen, nitrogen, and sulfur
What explains the occurrence of polar bonds?
different electronegativity values
electronegativity
tendency of an atom to attract electrons
valence shell
outermost shell of an atom
valence electron
electrons that reside in the outermost shell of an atom
group
atoms that have the same number of valence electrons
chemical equilibrium
established when the forward and reverse reactions are happening at equal rates; does not necessarily mean that the concentrations of reactants and products will be equal
intermolecular hydrogen bonds
molecules in which a hydrogen atom is directly bounded to a highly electronegative atom
What are the most highly electronegative elements?
oxygen, nitrogen, sulfur, fluorine
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