Chapter 2 The Chemical Context Flashcards
Element
Any substance that cannot be broken down to any other substance by chemical reactions
Matter
Anything that takes up space and has mass
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
Trace Element
An element indispensable for life but required in extremely minute amounts
Atom
The smallest unit of matter that refrains the properties of an element
Neutron
A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 X 10*-24g, found in the nucleus of an atom
Proton
A subatomic particle with a single positive electrical charge, with a mass of about 1.7 X 10*-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 os a neutron or 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 the nucleus of an atom, unique for each element and designated by a subscript
Mass Number
The sum of the 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
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
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
Electron Shell
An energy level of electrons at a characteristic average distance from the nucleus of an atom
Valence Electron
An electron in the outermost electron shell
Valence Shell
The outermost energy shall 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
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
Valence
The bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom’s outer-most (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 share equally between two atoms of similar electronegativity
Polar Covalent Bond
A covalent bond between atoms tat 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 attraction between oppositely charged ions
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 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
Chemical Reaction
The making and breaking of chemical bonds, leading to changes in the composition of matter
Reactant
A starting material in a chemical reaction
Product
A 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
