Chapter 2 Flashcards
Matter
Anything that takes up space and has mass.
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.
Trace element
An element indispensable for life but required in extremely minute amounts.
Atom
The smallest unit of matter that retains the properties of an element.
Neutron
A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7x10 g, found in the nucleus of an atom.
Proton
A subatomic particle with a single positive electrical charge, with a mass of about 1.7x10 g, found int he nucleus of an atom.
Electron
A subatomic particle with a single negative electrical charge and mass about 1/2000 that of a neutron or proton.
One or more electrons move around the nucleus of an atom.
Atomic nucleus
An atoms 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 atoms 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 accruing 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 the atomic mass.
Radioactive isotope
An isotope (an atomic form of a chemical element) that is unstable
The nucleus decays spontaneously, give 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 mater possesses as a result of its location or spatial arrangement (structure).
Electron shells
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 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 more 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 guy two atoms.
Valence
The bonding capacity of a given atom.
Usually equals the number of unpaired electrons required to complete the atoms 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
Salt
A compound resulting from the formation of an ionic bond.
Also called an ionic compound
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 changes.
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 to not change with time.
