Presentation is loading. Please wait.

Presentation is loading. Please wait.

Periodic Trends.

Similar presentations

Presentation on theme: "Periodic Trends."— Presentation transcript:

1 Periodic Trends

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

3 Trends in Atomic Size First problem: Where do you start measuring from? The electron cloud doesn’t have a definite edge. They get around this by measuring more than 1 atom at a time.

4 Period Trend: Atomic Radius

5 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

6 Influenced by three factors: 1. Energy Level
Trends in Atomic Size Influenced by three factors: 1. Energy Level Higher energy level is further away. 2. Charge on nucleus More charge pulls electrons in closer. 3. Shielding effect: e <-> e repulsion

7 Table of Atomic Radii


9 Periodic Trend: Ionization Energy

10 Ionization Energy Definition: the energy required to remove an electron from an atom 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

11 Periodic Trend: Electronegativity

12 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

13 Periodic Table of Electronegativities

14 Summary of Periodic Trends

15 Ionic Radii Cations Anions Positively charged ions formed when
an atom of a metal loses one or more electrons Cations Smaller than the corresponding atom Negatively charged ions formed when nonmetallic atoms gain one or more electrons Anions Larger than the corresponding atom

16 Graphic courtesy Wikimedia Commons user Popnose

17 p.190, figure 6.14 Ionic size decreases Ionic size increases

Download ppt "Periodic Trends."

Similar presentations

Ads by Google