Chapter 2: The Chemical Context of Life Flashcards
matter
anything that takes up space and has mass
- composed of elements
element
any substance that cannot be broken down to any other substance by chemical reactions
compound
a substance consisting of two or more different elements combined in a fixed ratio
essential element
a chemical element required for an organism to survive, grow, and reproduce
carbon, hydrogen, oxygen, nitrogen
make up 96% of living matter
calcium, phosphorus, potassium, sulfur
most of the remaining 4% of living matter
trace elements
an element indispensable for life but required in extremely minute amounts
atom
the smallest unit of matter that retains the properties of an element
- composed of subatomic particles
neutron
a subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7x10^-24g, found in the nucleus of an atom
proton
a subatomic particle with a single positive electrical charge, with a mass of about 1.7x10^-24g, found in the nucleus of an atom
electron
- a subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or a proton
- one or more electrons move around the nucleus of an atom
atomic nucleus
an atom’s dense central core, containing protons and neutrons
dalton
- a measure of mass for atoms and subatomic particles
- the same as the atomic mass unit, or amu
atomic number
the number of protons in its nucleus of an atom, unique for each element and designated by a subscript
mass number
the total number of protons and neutrons in an atom’s nucleus
atomic mass
- the total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom
- for an element with more than one isotope, the atomic mass is the average mass of the naturally occurring isotopes, weighted by their abundance
isotope
one of several atomic forms of an element, each with the same number of protons, but a different number of neutrons, thus differing in atomic mass
radioactive isotope
- an isotope (an atomic form of a chemical element) that is unstable
- the nucleus decays spontaneously, giving off detectable particles and energy
radioactive tracers
can be used to track atoms through metabolism and can also be used in combination with sophisticated imaging instruments
PET scanners
can monitor the growth and metabolism of cancers in the body
half-life
the amount of time it takes for 50% of a sample of a radioactive isotope to decay
radiometric dating
a method for determining the absolute age of rocks and fossils, based on the half-life of radioactive isotopes
energy
the capacity to cause change, especially to do work (to move matter against an opposing force)
potential energy
the energy that matter possesses as a result of its location or spatial arrangement (structure)
lowest
matter has a natural tendency to move toward the ________ possible state of potential energy
electron shells
an energy level of electrons at a characteristics average distance from the nucleus of an atom
chemical behavior of an atom
determined by the distribution of electrons in the electron shell
periodic table of the elements
shows the electron distribution for each element
valence electron
an electron in the outermost electron shell
valence shell
the outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom
orbital
the three-dimensional space where an electron is found 90% of the time
chemical bond
- an attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms
- the bonded atoms gain complete outer electron shells
covalent bond
a type of strong chemical bond in which two atoms share one or more pairs of valence electrons
molecule
two or more atoms held together by covalent bonds
single bond
- a single covalent bond
- the sharing of a pair of valence electrons by two atoms
double bond
- a double covalent bond
- the sharing of two pairs of valence electrons by two atoms
structural formation
the notation used to represent atoms and bonding
- H–H represents a single bond
- O=O represents a double bond
valence
- the bonding capacity of a given atom
- the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell
electronegativity
the attraction of a given atom for the electrons of a covalent bond
nonpolar covalent bond
a type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity
polar covalent bond
- a covalent bond between atoms that differ in electronegativity
- the shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive
ion
an atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge
cation
a positively charged ion
anion
a negatively charged ion
ionic bond
a chemical bond resulting from the attraction between oppositely charged ions
ionic compound
- a compound resulting from the formation of an ionic bond
- also called a salt
hydrogen bond
a type of weak covalent bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule
Van der Waals interactions
weak attractions between molecules or parts of molecules that result from transient local partial charges
molecular shape
determines how biological molecules recognize and respond to one another
chemical reaction
the making and breaking of chemical bonds, leading to changes in the composition of matter
reactants
a starting material in a chemical reaction
product
the material resulting from a chemical reaction
chemical equilibrium
in a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time
