A particle of matter with a positive electrical charge and a mass of 1 amu or 1.67E -24g. Although a proton has a mass 1837 times greater than an electron, it is nearly identical in mass to

In measurement indicates a set of measurements that are very similar. They may or may not be close to the true answer.

A positive integer constant that determines the principal energy level of an electron. Sometimes it is designated by the letters K, L or M. Related information.

a positively charged particle of antimatter that has the same mass and spin of an electron.

A scale ranging from 0 to 14, which is used to determine how acidic or basic a substance is. The pH of a substance is determined by taking the negative of the logarithm of the molar hydrogen

While groups are characterized by the number of electrons present in the outer shell, periods are characterized by the number of energy levels (shells) of electrons surrounding the nucleus.

an arrangement of elements in a geometric pattern designed to represent the periodic law by aligning elements into periods and groups. Elements with the same number of orbitals are in the sa

The electron configurations of the atoms of the elements vary periodically with their atomic number. Consequently, all properties of the elements that depend on their electron configuration

Either the actual charge of an atom (ion) in a substance, assuming the atom exists as a monatomic ion, or a hypothetical charge assigned by simple rules. 2) The charge an atom would have in

the quantum theory matter that combines Schrodinger's wave mechanics and Heisenburg's uncertainty principle and applies this to the behavior and nature of electrons. Orbital theory was formu

the area around an atom where according to orbital theory the probability of finding an electron is the greatest.

elements that are present in the gaseous state as single atoms. These elements are the noble gasses: He, Ne, Ar, Kr, Xe and Rn.

a complete chemical unit. While a molecule is often thought of as consisting of more than one atom, this is not always true. For instance, helium has only one atom per molecule. The oxygen m

is the basic unit of measurement in chemistry. By definition, in modern chemistry, one mole represents the number of carbon atoms in exactly 12 grams of carbon 12 (C12).

is a unit that enables scientists to calculate the weight of any chemical substance, be it an element or a compound. Molar mass is the sum of all of the atomic masses in a formula. More info

the number of moles of a solute dissolved in a liter of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molarity is

is the number of moles of solute dissolved in one kilogram of solvent. Note: be careful not to confuse molality and molarity. Molality is represented by a small "m," whereas molari

Forms or species of an element that has the same numbers of protons (hence the same atomic number), but different numbers of neutrons, thus different atomic masses. Technically speaking if a

elements that do not exhibit the characteristics of metals. These elements differ markedly from metals in respect to electronegativity and thermal and electrical conductivity. These elements

elements belonging to Group 18 of the periodic table. These elements are very unreactive, however, they are not nonreactive as compounds containing these elements have been synthesized. Ther