Electronegativity
A measure of the ability of an atom to attract the electrons in a bond.
Electron spin
The intrinsic angular momentum of an electron, having arbitrary values of and . See Spin
quantum number.
Element
A substance that cannot be further broken down by chemical means. All atoms of a given element
have the same number of protons.
Emission spectrum
The spectrum produced by a species emitting energy as it relaxes from an excited to a lower energy
state.
Empirical formula
The simplest whole-number ratio of the different elements in a compound.
Endothermic reaction
A reaction that absorbs heat from the surroundings as the reaction proceeds (positive ∆H).
End point
The point in a titration at which the indicator changes color, showing that enough reactant has been
added to the solution to complete the reaction.
Enthalpy (H)
The heat content of a system at constant pressure. The change in enthalpy (∆H) in the course of a
reaction is the difference between the enthalpies of the products and the reactants.