Periodic Trends

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Slide 1

Periodic Trends

Slide 2

CA Standards

Students know how to use the periodic table to identify trends in ionization energy, electronegativity, and the relative sizes of ions and atoms.

Slide 3

Atomic Radius

Definition: Half of the distance between nuclei in covalently bonded diatomic molecule

Radius decreases across a period

Increased effective nuclear charge due to decreased shielding

Radius increases down a group

Each row on the periodic table adds a “shell” or energy level to the atom

Slide 4

Table of Atomic Radii

Slide 5

Period Trend: Atomic Radius

Slide 6

Ionization Energy

Tends to increase across a period

As radius decreases across a period, the electron you are removing is closer to the nucleus and harder to remove

Tends to decrease down a group

Outer electrons are farther from the nucleus and easier to remove

Definition: the energy required to remove an electron from an atom

Slide 7

Periodic Trend: Ionization Energy

Slide 8

Electronegativity

Definition: A measure of the ability of an atom in a chemical compound to attract electrons

Electronegativity tends to increase across a period

As radius decreases, electrons get closer to the bonding atom’s nucleus

Electronegativity tends to decrease down a group or remain the same

As radius increases, electrons are farther from the bonding atom’s nucleus

Slide 9

Periodic Table of Electronegativities

Slide 10

Periodic Trend: Electronegativity

Slide 11

Summary of Periodic Trends

Slide 12

Ionic Radii

Cations

Positively charged ions formed when

an atom of a metal loses one or

more electrons

Smaller than the corresponding

atom

Anions

Negatively charged ions formed

when nonmetallic atoms gain one

or more electrons