Chapter 2: The Chemical Context of Life Flashcards
organisms are made of what
matter
is a substance that cannot be broken
down to other substances by chemical reactions
element
is a substance consisting of two or
more elements in a fixed ratio
compound
elements required for life
essential elements
how much of a percentage are natural elements
20-25% of the 92
Carbon, hydrogen, oxygen, and nitrogen make up how many percentage of living matter
96%
are required by an organism in only
minute quantities
trace elements
is the smallest unit of matter that still
retains the properties of an element
atom
Atoms are composed of what
subatomic particles
dense core
nucleus
what composes the nucleases
protons and neutrons
form a “cloud” of negative charge around
the nucleus
electrons
Neutron mass and proton mass are almost identical
and are measured in
Daltons
is the number of
protons in its nucleus
atomic number
is the sum of protons
plus neutrons in the nucleus
mass number
the atom’s total mass,
atomic mass
how is the chemical behavior of an atom determined
the distribution of electrons in electron shells
the distribution of electrons in electron shells
isotopes
decay spontaneously, giving
off particles and energy
radioactive
A “parent” isotope decays into its “daughter” isotope
at a fixed rate, expressed as the
half-life
scientists measure the ratio
of different isotopes and calculate how many half-
lives have passed since the fossil or rock was
formed
radiometric dating
is the capacity to cause change
energy
is the energy that matter has
because of its location or structure
Potential energy
An electron’s state of potential energy is called its
energy level
electron shell
electrons in the outermost shell,
valence electrons
outermost electron shell
valence shell
what determines the chemical behavior of an Atom
valence electrons
Elements with a full valence shell are what
chemically inert
the three-dimensional space where an electron is found 90% of the time is called what
orbital
atoms are held by attractions called what
chemical bonds
is the sharing of a pair of valence
electrons by two atoms
covalent
consists of two or more atoms held
together by covalent bonds
molecule
is the
sharing of one pair of valence electrons
single bond
is the
sharing of two pairs of valence electrons
double bond
is an atom’s attraction for the
electrons in a covalent bond
Electronegativity
the atoms share the
electron equally
nonpolar covalent bond
one atom is more
electronegative, and the atoms do not share
the electron equally
polar covalent bond
Unequal sharing of electrons causes what
partial positive or negative charge for each atom
or molecule
A charged atom (or molecule) is called an
ions
is a positively charged ion
cation
negatively charged ion
anion
an attraction between an anion and
a cation
ionic bond
Compounds formed by ionic bonds are called
ionic
compounds, or salts
Most of the strongest bonds in organisms are
covalent bonds that form a cell’s molecules
Many large biological molecules are held in their
functional form
weak bonds
forms when a hydrogen atom
covalently bonded to one electronegative atom is
also attracted to another electronegative ato
hydrogen atoms
In living cells, the electronegative partners are what
oxygen or nitrogen atoms
are attractions between
molecules that are close together as a result of
these charges
Van der Waals interactions
are the making and breaking of
chemical bonds
Chemical reactions
The starting molecules of a chemical reaction are
called
reactants
The final molecules of a chemical reaction are called
products
