Periodic Trends, Ionic Bonding, and Polyatomic Ions (VOCABULARY)

A vocabulary deck covering key concepts from the lecture notes: noble gases, octet rule, ions and bonding, periodic table trends, metalloids, and common ionic/polyatomic species.

Noble gas

Chemically inert elements with completely full outer electron shells, making them stable and nonreactive.

Octet rule

Atoms gain or lose electrons to achieve a full outer energy level of eight electrons, achieving stability.

Ion

A charged particle formed when atoms gain or lose electrons to reach a stable electron configuration.

Cation

A positive ion formed when an atom loses electrons; metals typically form cations.

Anion

A negative ion formed when an atom gains electrons; nonmetals typically form anions.

Ionic bond

A bond formed by the electrostatic attraction between oppositely charged ions after electron transfer.

Ionic compound

A compound composed of cations and anions, usually forming crystalline salts such as NaCl.

Sodium fluoride (NaF)

An ionic compound made of Na+ and F-; example of a salt with a +1 and a -1 charge.

Group charges (main-group elements)

In main-group elements, ionic charges follow group number: Group 1 +1, Group 2 +2, Group 3 +3; Group 7 -1, Group 6 -2, Group 5 -3; transition metals can have multiple charges.

Polyatomic ion

A charged entity made of two or more atoms (e.g., NO3-, SO4^2-, PO4^3-, NH4+).

Nomenclature of ionic compounds

Naming by balancing charges; transition metals may require indicating the charge in the name (e.g., CuCl = copper(I) chloride; MgSO4 = magnesium sulfate).

Group (chemical family)

Vertical columns in the periodic table; elements in a group have the same number of valence electrons and similar chemical properties.

Valence electron

An electron in the outermost energy level; the number of valence electrons generally equals the group number for main-group elements.

Period

A horizontal row on the periodic table; the period number corresponds to the number of energy levels (shells) in the atom.

Staircase (metalloids border)

A diagonal line on the periodic table; elements touching the staircase are metalloids (semimetals); left are metals, right are nonmetals.

Metal vs nonmetal

Metals lie to the left of the staircase; nonmetals to the right; most elements are metals, many common substances (like biological matter) are nonmetals.

Metalloids (semimetals)

Elements that border the staircase with properties between metals and nonmetals, often acting as semiconductors.

Sulfur (S)

Atomic number 16; period 3; group 16; outer energy level has 6 electrons and tends to gain 2 electrons to form S^2− (sulfide).

Multivalent transition metals

Transition metals that can have more than one oxidation state (e.g., copper(I)/copper(II); iron(II)/iron(III)); the charge is indicated in the name.

Covalent bond

Bond formed by sharing electrons between nonmetals; most compounds are covalent, while salts are ionic.

Example polyatomic ions

Nitrate NO3−, sulfate SO4^2−, phosphate PO4^3−, ammonium NH4+; these ions behave like single ions in compounds.