Ch.8 - Periodic Properties of the ElementsSee 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

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?

Additional Problems
For the following sets of atoms, write an “L” above the one that is largest, and an “S” above the one that is smallest
In moving from top to bottom in the same column on the periodic table, what trend is expected for atomic size and why?A. Increase because the nucleus is getting strongerB. Increase because electrons are being placed in higher n-valuesC. Decrease because the nucleus is getting strongerD. Increase because electrons are being added to degenerate orbitalsE. Decrease because electrons are being placed in higher n-values
Which atom below has the largest atomic radius?A. LiB. NC. NaD. SE. Cl
Which alkaline earth metal has the smallest atomic radius?
In which group do the atoms become larger in going down the group?a) group 1Ab) group 4Ac) group 5Ad) group 7Ae) groups 1A, 4A, 5A, and 7A
Of the following, which gives the correct order for atomic radius for Mg. Na, P. Si and Ar?A) Mg>Na> P> Si> ArB) Ar> Si> P > Na > MgC) Si> P> Ar>Na > MgD) Na > Mg> Si> P> ArE) Ar> P> Si > Mg>Na
Rank these elements according to atomic radius. Largest to smallest radiusSiPSClArNaMgAl
Place the following atoms in order of increasing atomic radii (smallest to largest):S, Cl, Se, and As.a. Cl < S < Se < Asb. S < Cl < As < Sec. S < Cl < Se < Asd. As < Se < S < Cle. Se < As < S < Cl
Which of the following correctly lists the five atoms in order of decreasing size (largest to smallest)?             Ca,       K,       Ne,         O,         Pa) P > Ne > Ca > K >Ob) O > Ca > K > P > Nec) F > O > P > Ca > Kd) K > Ca > P > O > Nee) Ca > P > O > Ne > K
Rank the following elements in order of decreasing atomic radius. Rank from largest to smallest radius. To rank items as equivalent, overlap them.a) Rb, Na, K, Lib) Li, Be, B, N
The size of metal atomsa) generally increases progressively from top to bottom in a group in the periodic table.b) generally increases progressively from left to right in a period.c) are smaller than those of the corresponding ions.d) do not change upon losing electrons.
Which of these elements has the  smallest  atomic radius?a) fluorineb) chlorinec) bromined) iodine
The atomic radius of main-group elements generally decreases from left to right across a row (or period), because the __________.        A. effective nuclear charge decreasesB. principal quantum number of the valence orbitals increasesC. number of core electrons increasesD. effective nuclear charge increasesE. principal quantum number of the valence orbitals decreases
Which of these atoms will be the  smallest ?a) Si (Z = 14)b) P (Z = 15)c) Ge (Z = 32)d) As (Z = 33) 
Which one of the following elements would be expected to have the  largest atomic radius? a) Lib) Csc) Fd) Bre) I
Consider the following radii:
Place the following in order of decreasing atomic radius.              As              S                F A. As > F > SB. S > As > FC. F > As > SD. As > S > FE. S > F > As
Consider the following atoms: Br, Sn, Sb, Te, I. What has the largest atomic radius?a. Brb. Snc. Sbd. Tee. IWhich is the most paramagnetic?a. Brb. Snc. Sbd. Tee. IWhat has the largest ionization energy?a. Brb. Snc. Sbd. Tee. IWhich has the largest electronegativity?a. Brb. Snc. Sbd. Tee. I
The atomic radius of main-group elements generally increases down a column because __________.A. effective nuclear charge decreases down a columnB. the mass of an atom increases down a columnC. the highest principal quantum number of the valence orbitals increasesD. effective nuclear charge increases down a columnE. both effective nuclear charge increases down a column and the principal quantum number of the valence orbitals increases
In general, atomic size tends to increase1. from top to bottom and from left to right on the periodic table.2. from bottom to top and from right to left on the periodic table.3. There is no relationship between the size of an atom and its position on the periodic table.4. from bottom to top and from left to right on the periodic table.5. from top to bottom and from right to left on the periodic table. 
Circle the largest atom:Cl    P
Which element has the largest atomic radius?a. Na or Lib. Zr or Lac. Sb or S
Rank the following elements in order of decreasing atomic radius. Rank from largest to smallest radius. To rank items as equivalent, overlap them.F, C, O, B
Arrange the following elements in order of decreasing atomic radius: Cs, Sn, Cl, Pb, and As Rank elements from largest to smallest.  
Arrange these elements according to atomic radius.  
The atomic radius of bromine is larger than the atomic radius of _____.a. chlorineb. uraniumc. potassiumd. iodinee. xenon 
Which of these atoms has the smallest radius? (a) Al (B) P (C) As (D) Te (E) Na
Rank the following atoms according to size: As, Cl, Se, F