The Periodic Table: Trends of Atomic Properties Lecture 24

Aufbau principle is an approach to determine the electron configurations of the elements starting at the beginning of the periodic table and adding one electron per element to the lowest energy orbital available.

All physical and chemical behavior of the elements is based ultimately on the electron configurations of their atoms.

Properties are periodic if they generally increase or decrease in a recurring manner throughout the periodic table.

Properties directly influenced by electron configuration: Atomic size; Ionization energy; Electron affinity.

Atomic size;

Ionization energy;

Electron affinity.

What is atomic size?

What is atomic size?

Key trends in atomic radius: Atomic radius generally increases in a group from top to bottom; Atomic radius generally decreases in a period from left to right.

Atomic radius generally increases in a group from top to bottom;

Atomic radius generally decreases in a period from left to right.

A sample problem on ranking elements by atomic size.

What is ionization energy?

First ionization energies of the main-group elements

Key trends in ionization energy: Ionization energy generally decreases down a group; Ionization energy generally increases across a period.

Ionization energy generally decreases down a group;

Ionization energy generally increases across a period.

Ionization energy may be very high.

A sample problem on ranking elements by first ionization energy.

A sample problem on identifying an element from successive ionization energies.

What is electron affinity?

Key trends in electron affinity: Reactive nonmetals form negative ions in their ionic compounds; Reactive metals form positive ions in their ionic compounds; Noble gases tend not to lose or gain electrons.

Reactive nonmetals form negative ions in their ionic compounds;

Reactive metals form positive ions in their ionic compounds;

Noble gases tend not to lose or gain electrons.

THE END