Periodic Trends, Bond Types & Nomenclature

Effective Nuclear Charge (Zeff)

The net positive nuclear charge experienced by valence electrons after accounting for core electron shielding.

Periodic trend for Effective Nuclear Charge (Zeff)

Increases from left to right across a period; remains relatively constant down a group.

Periodic trend for Atomic Radius

Decreases across a period (due to increasing Zeff); increases down a group (due to additional electron shells).

Size comparison: Cation vs. neutral parent atom

A cation is smaller than its parent atom due to electron loss and reduced electron-electron repulsion.

Size comparison: Anion vs. neutral parent atom

An anion is larger than its parent atom due to added electron-electron repulsion.

Definition of First Ionization Energy (IE1)

The energy required to remove the most loosely held valence electron from a gaseous neutral atom.

General periodic trend for First Ionization Energy

Increases across a period (electrons held tighter); decreases down a group (electrons further away).

Definition of Electron Affinity (EA)

The energy change that occurs when an electron is added to a gaseous neutral atom.

Energy requirement of bond breaking vs. bond formation

Bond breaking always requires energy (+ΔH); bond formation releases energy (-ΔH).

Electronegativity difference (ΔEN) threshold for Pure (Nonpolar) Covalent bonds

ΔEN < 0.4.

Electronegativity difference (ΔEN) threshold for Polar Covalent bonds

ΔEN between 0.4 and 1.8.

Electronegativity difference (ΔEN) threshold for Ionic bonds

ΔEN > 1.8.

Most electronegative element on the periodic table

Fluorine (F with a value of 4.0).

General naming convention for Binary Ionic Compounds

[Metal name] + [nonmetal stem with "-ide"], without numerical prefixes.

System used to specify charges on variable-charge transition metal cations

Stock system using Roman numerals in parentheses (e.g., Fe3+ = Iron(III)).

Chemical formula of Tin(IV) oxide

SnO2 (balances Sn4+ and two O2- ions).

Chemical formula and correct name of Fe2(SO4)3

Iron(III) sulfate.

Naming rule for Binary Acids (acids containing only H and one other element)

hydro- + [element stem] + -ic acid (e.g., HCl = hydrochloric acid).

Naming rule for Oxyacids derived from polyatomic anions ending in "-ate"

[Root] + -ic acid (no "hydro-" prefix; e.g., HNO3 = nitric acid).

Naming rule for Oxyacids derived from polyatomic anions ending in "-ite"

[Root] + -ous acid (no "hydro-" prefix; e.g., HNO2 = nitrous acid).

Correct chemical formula for Phosphorous acid

H3PO3 (derived from phosphite, PO3^3-).

Correct name for binary covalent molecule N2O4

Dinitrogen tetroxide (requires numerical Greek prefixes).

List of the Seven Diatomic Elements

H2, N2, O2, F2, Cl2, Br2, I2.

Proper nomenclature for an ionic hydrate such as CuSO4 · 5H2O

Copper(II) sulfate pentahydrate.