Chapter 2 - Small Molecules and the Chemistry of Life Flashcards
Atom
Smallest unit of matter
Atomic Mass
Measurement of the quantity of matter present
Atomic Mass Unit (AMU)
Mass of one proton or neutron
Element
Pure substance composed of only one kind of atom
Number of protons are unique to each element
Atomic Number
Number of protons
Mass Number
Number of protons and number of neutrons in an atom’s nucleus
Atomic Weight
Average of mass numbers of isotopes
Isotopes
Forms of an element with different number of neutrons
Different mass numbers
Hydrogen
Element with 1 proton, 0 neutrons
Deuterium
Hydrogen isotope
1 proton, 1 neutron
Tritium
Hydrogen isotope
1 proton, 2 neutrons
Heavy water
Radioisotopes
Unstable isotopes that spontaneously give off energy in the form of α, β, and γ radiation from the nucleus
The release of energy transforms the original atom
Molecule
Stable association of atoms
Electron
Number of electrons determine how atoms will interact
Orbital
Region where electrons are found 90% of the time
Can be occupied by 2 electrons
Electron Shell
Energy levels around the nucleus of an atom
First shell contains one s orbital (2 electrons)
Second shell contains 1 s and 3 p orbitals (8 electrons)
Valence Shell
Outermost electron shell
Determines how the atom interacts with other atoms (chemical reaction)
Reactive atoms have unpaired electrons in valence shell
Chemical Bond
Attractive force that links atoms together to form molecules
Covalent Bond
Sharing of at least one pair of electrons so that the outer shell is filled
Strongest of chemical bonds
Valence
Number of bonds an atom can form depending on the number of valence electrons
Compound
Molecule made of up two or more elements bound together in a fixed ratio
Molecular Weight
Sum of all atomic weights of all atoms in the molecule
Nonpolar Covalent Bond
Equal sharing of electrons
Polar Covalent Bond
Unequal sharing of electrons when electrons are drawn to one nucleus more than to the other
Partial negative charge near the strongly electronegative atom
Partial positive charge near the weakly electronegative atom
Electronegativity
Measure of degree of attraction between nucleus and electrons
Higher value = greater attraction of pairing elctrons to the receiving nucleus
Ion
Electrically charged particles that form when atoms gain or lose one or more electrons
Cations
Positively charged ions; one less electron than protons
Anions
Negatively charged ions; one more electron than protons
Ionic Attraction
Bond formed as a result of the electrical attraction between ions of opposite charges
Hydrogen Bond
Negatively charged oxygen atom of one water molecule is attracted to the positively charged hydrogen atom of another water molecule; intramolecular
Hydrophilic Interactions
A polar molecule interacts with water; “water-loving”
Hydrophobic Interactions
Nonpolar molecules interact with other nonpolar molecules; “water-hating”
Chemical Reactions
Loss or gain of electrons, with reactants combined on the left to create products on the right
Oxidation
Chemical reaction with a loss of electrons (LEO - loss of electrons equals oxidation)
Reduction
Chemical reaction with a gain of electrons (GER - gain of electrons equal reduction)
Energy
Capacity to do work
Water
A polar molecule that can form hydrogen bonds; tetrahedral shape (not a linear shape)
Solute
Substance being dissolved
Solvent
Liquid that dissolves a substance
Mole
Amount of substance (grams) that is numerically equal to its molecular weight; 1 mole for any substance is 6.02 x 10^-23 molecules per mole
1 Molar Solution
1 mole of a substance dissolved in water to make 1 L
Acids
Substances that release H+; higher concentration of H+; pH level 1-7
Bases
Substances that accept H+; lower concentration of H+; pH level 7-14
pH
A numeric scale used to specify the acidity or basicity of an aqueous solution; each pH value up or down represents a 10 fold increase/decrease in hydrogen ion concentration [H+]
Buffer
A weak acid or base used to prevent a rapid change in pH when acids or bases are added to the solution; to maintain homeostasis
