Ionization Energies & Periodic Trends — Quick Notes

Ionization energies and valence electrons

• Large jump in successive ionization energies signals removal of a core electron; small steps correspond to valence electrons.

• Example: big jump between the 3rd and 4th ionization energies: $IE<em>3 \to IE</em>4$, so $\Delta IE = IE<em>4 - IE</em>3 \gg 0$.

• This implies the element has $n_v = 3$ valence electrons (three valence removals before a core electron is removed).

Periodic trends: metals vs nonmetals

• Metals: located on the left; reactivity $\uparrow$ down a group and $\downarrow$ across a period.

• Nonmetals: located on the upper-right; reactivity tends to increase toward the nonmetal side.

• Metalloids: lie around the stair-step; exhibit metallic physical properties but nonmetallic chemical properties.

Metalloids and the stair-step

• Metalloids reside around the stair-step line; they separate metals and nonmetals.

• They have visible metallic properties but chemical behavior closer to nonmetals.

Reactivity trends

• Metals: reactivity increases down a group and decreases across a period.

• Nonmetals: reactivity increases as you move toward the nonmetal side (toward the upper-right).

Exam tips

• Show up to the exam on Thursday; being present helps performance.

• Exams can cause anxiety; being prepared and taking the exam as scheduled is recommended.