Ch.2 The Chemical Context of Life Flashcards
Element
A substance that cannot be broken down to other substances by chemical reactions
Compound
A substance consisting of two or more different elements combined in a fixed ratio
Essential element
Chemical elements required for an organism to survive, grow, and reproduce
Trace elements
Required by an organism in only minute quantities
Atom
The smallest unit of matter that still retains the properties of an element
Atomic nucleus
Atoms dense central core containing protons and neutrons
Atomic number
Number of protons and neutrons in the nucleus of an atom
Mass number
The total number of protons and neutrons in the nucleus of an atom
Atomic mass
Total mass of an atom
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
One in which the nucleus decays spontaneously, giving off particles and energy
Half-life
The time it takes for 50% of the parent isotope to decay
Energy
The capacity to cause change, for instance, by doing work
Potential energy
Energy that matter possesses because of its location or structure
Valence electrons
Electrons in the outermost shell
Valence shell
Outermost electron shell
Chemical bonds
An attraction between two atoms, resulting from a sharing of outer shell electrons or the presence of opposite charges on the atoms
Covalent bond
The sharing of a pair of valence electrons by two atoms
Molecule
Two or more atoms held together by covalent bonds
Single bond
A pair of shared electrons
Double bond
Double covalent bonds; the sharing of two pairs of valence electrons by two atoms
Valence
The bonding capacity of a given atom
Compound
Combination of two or more different elements
Electronegativity
The attraction of a particular 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
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.
Ions
An atom, or group of atoms, that has gained or lost one or more electrons, thus acquiring a charge
Cation
Positively charged ion
Anion
Negatively charged ion
Hydrogen bond
A type of weak chemical 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
Van der Waals interactions
Weak attractions between molecules or parts of molecules that result from transient local partial charges
Chemical reactions
The making and breaking of chemical bonds, leading to changes in the composition of matter
Chemical equilibrium
The point at which the reactions offset one another exactly
Radioactive isotopes
Decay spontaneously gives off particles of energy
Metabolism
The sum total of chemical processes in your body
How are radioactive tracers used?
Can be used to track atoms through metabolism
In combination with sophisticated instruments
As diagnostic tools in science
What happens when bonds are made?
Energy is released
“Fixing”
Taking that element from a gas and doing something to turn it into a solid
What do weak bonds provide?
In large numbers, they can provide strength and stability
Allow for more change
What do covalent bonds provide?
Stability because they are harder to break
