accuracy.

acid. Compounds having the following properties are classified as acids:

  1. compound is covalent;
  2. compound contains hydrogen;
  3. Acids are characterized by the following properties: anion.

atomic size.

atomic radius. Same as atomic size.

atomic number. The number of positive charges of an element that are to be found in the nucleus of one atom of that element, or in other words, the number of protons the atom has. The atomic numbers for the elements are listed on the periodic chart.

atomic mass. The mass of one atom of an element expressed in amu’s (u’s).

atomic mass unit. Abbreviated “u”, or by older standards, “amu”, a unit of mass measure, 12 of which are equal to the mass of one carbon-12 atom. Since carbon-12 atoms have a 1-to-1 ratio of neutron’s to protons (6 neutrons, 6 protons), from this carbon-12 standard the definition of 1 amu is derived as the average mass of one neutron and one proton.

balanced equation. A chemical equation having the same number of each kind of atom and the same electrical charge on each side of the equation.

base. A metallic hydroxide, i.e. an ionic compound containing $\ce{OH-}.$

binary compound.

cation.

chemical formula.

chemical properties. The ability of a substance to form new substances either by reaction with other substances or by decomposition.

concentration unit.

covalent bond. A chemical bond formed between two atoms by sharing a pair of electrons.

covalent compound. If elements bond in a manner in which a sharing of electrons occurs but no electrons are transferred from one element to the other, the resultant bond and compound are classified as covalent.

electron shell. A collection of orbitals at approximately the same average distance from the nucleus. Electron shells are designated by a number, called the principal quantum number, and each shell can only contain a maximum number of orbitals. Electron shells are filled with electrons in a specific order. If an electron shell is the first to be filled with electrons, it is called the 1st electron shell or shell 1. The second electron shell to be filled is shell 2, and so one. Each succeeding electron shell is a greater distance from the nucleus than the one before it. The $\nth$ electron shell can contain a maximum of $n^2$ orbitals and $2n^2$ electrons. (The coefficient of 2 is the maximum number of electrons each orbital of the $n^2$ orbitals can have.) The first electron shell will fill with electrons first until it reaches its limit of $2(1^2)=2$ electrons, then the second shell will fill until it reaches its limit of $2(2^2)=8$ electrons, then the third shell will fill until it reaches its limit of $2(3^2)=18$ electrons, and so on. On the periodic chart, the first row (or period) represents the first electron shell, the second period designates the second electron shell, the third period the third electron shell, and so on. The atomic number corresponds to the number of electrons each element has around its nucleus. Thus, for example, Argon, whose atomic number is 18, has 18 electrons around its nucleus, and its 18 electrons fill the electron shells in the manner described.

electron subshell. An electron subshell is a subdivision of an electron shell containing that collection of orbitals of the electron shell that are approximately the same average distance from the nucleus of the atom. This is a useful sub-classification since not all orbitals of an atom can always be the same average distance from the nucleus due to spatial constraints. Electron subshells are given the letter names $s$, $p$, $d$, and $f$. The $s$ subshell can contain a maximum of 1 orbital (2 electrons), the $p$ subshell a maximum of 3 orbitals (6 electrons), the $d$, 5 orbitals (10 electrons), and the $f$, 7 orbitals (14 electrons). Each electron shell only has as many subshells as it needs to meet its capacity of electrons, and all electron shells fill their subshells in the same order. Within an electron shell, $s$ subshells are closer to the nucleus than $p$ subshells, $p$ subshells are closer than $d$ subshells, and $d$ subshells are closer than $f$ subshells. However, the $s$ subshell in the second electron shell, for instance, is further from the nucleus than the $s$ subshell in the first electron shell. As each electron shell fills, the $s$ subshell fills first. If the $s$ subshell becomes full but the electron shell has not reached its capacity yet, then the $p$ subshell begins to fill after the $s$ subshell. If the $p$ subshell becomes full but the electron shell has not reached its capacity yet, then the $d$ subshell begins to fill after the $s$ subshell. If the $d$ subshell becomes full but the electron shell has not reached its capacity yet, then the $f$ subshell begins to fill after the $s$ subshell. If the $s$, $p$, $d$ or $f$ subshell of any electron shell becomes full and the electron shell reaches its capacity, then the next electron shell begins to fill starting with the $s$ subshell and repeating the entire pattern all over again. Note that because of the way subshells are defined, an electron shell meets its capacity if and only if the upper-most subshell of the electron shell also reaches its capacity. For instance, an $\ce{H}$ atom has one electron. Thus the first electron shell $(n=1),$ first subshell $(s)$, fills first. An atom of $\ce{He}$ has two electrons, so the first electron shell $(n=1),$ first subshell $(s),$ fills further. Since the $s$ subshell has exactly 1 orbital and thus a capacity of exactly 2 electrons, and since the first electron shell also has exactly 1 orbital and a capacity of exactly 2 electrons, it follows that the first electron shell and its uppermost subshell both reached their capacity at the same time. Carrying the example further, since

  1. the electron capacity of the first electron shell is $2(1^2)=2,$
    2. the electron capacity of the second electron shell is $2(2^2)=8,$
  2. the first electron shell fills first, the second shell fills second, etc., and
  3. $\ce{Ne}$ has 10 electrons;
it follows that $\ce{Ne}$ will have 2 electrons in the first electron shell and 8 electrons in the second electron shell. Of the 8 electrons in the second electron shell, the first 2 will fill the $s$ subshell of the second electron shell and the remaining 6 will fill the $p$ subshell of the second electron shell. But,
  1. the $s$ subshell has exactly 1 orbital and thus reaches its capacity at exactly 2 electrons,
  2. the $p$ subshell has exactly 3 orbitals and thus reaches its capacity at exactly 6 electrons,
  3. the sum of capacities between the two is $2+6=8$ electrons, and
  4. the second electron shell reaches its capacity at exactly $2(2^2)=8$ electrons.
Therefore, it follows that the second electron shell $(n=2)$ and its uppermost subshell $(p)$ both reached their capacity at the same time. One final characteristic of the pattern of electron-filling should be mentioned. Every orbital in a subshell is filled with 1 electron before each orbital is filled with its second electron. Thus, the $p$ subshell, which can contain a maximum of 3 orbitals, would fill all 3 orbitals with 1 electron each before filling all 3 orbitals with 1 more electron. Once all 3 orbitals are filled with 2 electrons, the next subshell within that electron shell begins to fill in the same manner.

electron configuration. There are two formats for showing how the electrons of an atom are configured. One is called the electron configuration format, the other is called the orbital diagram format. Electron configurations do not explicitly reflect the order in which orbitals are filled as just described, but they do show all other filling properties described earlier. Orbital diagrams, on the other hand, do reflect the order in which orbitals are filled, but involve drawing squares and arrows thus making them slightly more cumbersome to write.

electronegativity.

electrovalent bond. Same as ionic bond.

empirical formula. A chemical formula that gives the smallest whole-number ratio of atoms in a compound, that is, the relative number of atoms of each element in the compound; also known as the simplest formula.

energy level. Same as electron shell.

energy sublevel. Same as electron subshell.

homogeneous mixture. A mixture that exhibits only one phase. Also called solution.

formula mass. The sum of the atomic masses of the atoms within a formula unit.

formula unit. A formula unit is the ratio of elements in an ionic compound.

gas.

heterogenous mixture. A mixture that exhibits more than one phase.

hydride. A binary hydrogen compound.

hydroxide.

metallic hydroxide.

halide. A binary halogen compound.

ionic compound. When one or more electrons are transferred from one atom to another while forming a bond, the resultant bond is called an ionic bond, and the resulting compound is ionic.

ionization energy.

isoelectronic. An Ion that has the same electronic configuration as a given element is said to be isoelectronic to that element.

isotope. Atoms with the same atomic numbers but different mass numbers are isotopes of the element with the common atomic number.

law of constant compositions.

law of definite proportions. Same as law of constant composition.

liquid.

mass number. The number of positive and neutral charges of an element that are to be found in the nucleus of one atom of that element, or in other words, the number of protons and neutrons in the atom. This number is called the mass number since almost all of the mass of an atom is in its protons and neutrons, whereas mass from electrons is negligible.

metal. An element that is solid at room temperature and whose properties include luster, ductility, malleability, and good conductivity of heat and electricity.; metals tend to lose their valence electrons and become positive ions.

mixture. If a sample of matter possesses the following qualities, it is classified as a mixture:

  1. Its composition is variable.
  2. It may be separated into components by physical methods.
  3. Changes of state occur over a range of temperatures.
In loose terms, a mixture is a combination of substances which are physically but not chemically associated. When substances are so associated, these posses the three qualities just mentioned. There are two kinds of mixtures:
  • homogenous mixtures
  • heterogeneous mixtures.

molar mass. One mole is the amount of pure substance that contains the same number of particles as there are atoms in exactly 12 grams of carbon-12.

molecular formula.

molecular mass. The sum of the atomic masses of the atoms within a molecule.

nonmetal. An element that has properties opposite metals: lack of luster, relatively low melting point and density, and generally poor conduction of heat and electricity. Nonmetals may or may not be solid at room temperature; many are gases.

nonpolar covalent bond. A covalent bond between two atoms with the same electronegativity value; thus the electrons are shared equally between the two atoms.

orbital. A region in space around the nucleus of an atom in which there is a high probability of finding an electron. Each orbital can contain a maximum of 2 electrons

orbital diagram. There are two formats for showing how the electrons of an atom are configured. One is called the electron configuration format, the other is called the orbital diagram format. Electron configurations do not explicitly reflect the order in which orbitals are filled as just described, but they do show all other filling properties described earlier. Orbital diagrams, on the other hand, do reflect the order in which orbitals are filled, but involve drawing squares and arrows thus making them slightly more cumbersome to write.

outer electron configuration.

oxyanion. A polyatomic ion containing oxygen.

percent composition.

phase. A homogenous part of a system separated from other parts by a physical boundary.

physical properties.

polyatomic ion.

precision.

principal energy level of electron.

pure substance. A....

random errors. Errors that arise which are unrecognizable and which influence the results.

reactive. Elements that tend to undergo chemical changes and liberate energy are classified as reactive relative to those elements not as prone to such changes. Non-reactive substances remain unaltered, even under extreme conditions.

salt. An ionic compound that doesn’t contain $\ce{OH^-}$ or $\ce{O^2-}$.

shielding.

solid.

solute.

solution. Same as homogenous mixture.

solvent.

substance. A...

system. A body of matter under consideration.

systematic errors. Errors which result from

  1. poor procedures and methods,
  2. malfunctioning and uncalibrated instruments,
  3. human error,
  4. impure samples, and
  5. some unrecognized factors that influence the results.

theoretical yield. The maximum amount of product that can be produced according to a balanced equation.

valence configuration.