Ch.8 - Periodic Properties of the ElementsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Atomic radius represents the distance from the nucleus to the outer shell of an element. 

Trends in Atomic Radius

Concept #1: Understanding Atomic Radius


In this new video, we're going to take a look at atomic radius. Now we're going to say atomic radius is defined as half the distance between the nuclei in a molecule of two identical elements.
What does that mean? Well, remember we know that we have an element which is represented by a sphere. The diameter would just be the distance all the way across. The radius is just half of that, so our atomic radius is just that. And now if we are dealing a diatomic molecule we’d say that the sum of the radii equals the total distance between their two nuclei. That's what that definition is basically saying.
Now we're going to say it's important to remember the trend for atomic radius. So we’re going use this representation of the periodic table. So, the best strategy here is just to make a sheet with all the trends because there are tons of different types of periodic trends that you need to remember one can be atomic radius. So we're going to say generally, atomic radius will decrease as we go from left to right across a period. So it decreases going this way, and we going to say generally, it going to increase going down any group. So we going to say it increases going down this way. So just remember that trend in terms of atomic radii. 

For a diatomic molecule, atomic radius is defined as half the distance between the nuclei in a molecule of two identical elements.

Example #1: If the sum of the atomic radii of diatomic carbon is 154 pm and of diatomic chlorine is 198 pm, what is the sum of the atomic radii between a carbon and a chlorine atom. 

Practice: Which one of the following atoms has the largest atomic radius?