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

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
Using appropriate reference sources, look up the bond lengths of Xe-F bonds in several molecules. How do these numbers compare to the bond lengths calculated from the atomic radii of the elements?
In the previous sections, we have seen how the number of electrons and the number of protons affects the size of an atom or ion. However, we have not considered how the number of neutrons affects the size of an atom. Why not? Would you expect isotopes— for example, C-12 and C-13 —to have different atomic radii?
In April 2010, a research team reported that it had made Element 117. This discovery was confirmed in 2012 by additional experiments.Estimate a value for its atomic size based on its position in the periodic table.
Use the concepts of effective nuclear charge, shielding, and n value of the valence orbital to explain the trend in atomic radius as you move across a period in the periodic table.
As we move across a period of the periodic table, why do the sizes of the transition elements change more gradually than those of the representative elements?
The atomic radii of the isotopes of an element are identical to one another. However, the atomic radii of the ions of an element are significantly different from the atomic radii of the neutral atom of the element.Explain this behavior.
Choose the larger atom from each of the following pairs.Al or In
Choose the larger atom from each of the following pairs.Si or N
Choose the larger atom from each of the following pairs.P or Pb
Choose the larger atom from each of the following pairs.C or F
Arrange the following elements in order of decreasing atomic radius: Ca, Rb, S, Si, Ge, F.
Compare the elements bromine and chlorine with respect to the following properties.atomic radius
Consider the following elements: N, Mg, O, F, Al.Arrange the elements in order of decreasing atomic radius.
Consider the elements: B, C, N, O, F.Which element has the largest atomic radius?
Hydrogen is an unusual element because it behaves in some ways like the alkali metal elements and in other ways like nonmetals. Its properties can be explained in part by its electron configuration and by the values for its ionization energy and electron affinity.Is the following statement true? "Hydrogen has the smallest bonding atomic radius of any element that forms chemical compounds."
Consider the elements: Na, Mg, Al, Si, P.Which element has the largest atomic radius?
For main-group elements, give the observed trends in atomic radius as you move across a period in the periodic table.
For main-group elements, give the observed trends in atomic radius as you move down a column in the periodic table.
How to define atomic radius?
For transition elements, give the trends in atomic radius as you move across a period in the periodic table.
For transition elements, give the trends in atomic radius as you move down a column in the periodic table.
Which quantity must be determined experimentally in order to determine the bonding atomic radius of an atom?
Consider the metals in the first transition series. Use periodic trends to predict a trend in density as you move to the right across the series.
Table: Some Properties of the Halogens Element Electron Configuration Melting Point (oC) Density Atomic Radius (Å) I1 (kJ/mol) Fluorine [He]2s22p5 -220 1.69 g/L 0.57 1681 Chlorine [Ne]3s23p5 -102 3.12 g/L 1.02 1251 Bromine [Ar]4s23d104p5 -7.3 3.12 g/cm3 1.20 1140 Iodine [Kr]5s24d105p5 114 4.94 g/cm3 1.39 1008 Use the data from the table above to provide estimates for the atomic radius of an astatine atom?
Explain why atomic radius decreases as you move to the right across a period for main-group elements but not for transition elements.
Explain why vanadium (radius = 134 pm) and copper (radius = 128 pm) have nearly identical atomic radii, even though the atomic number of copper is about 25% higher than that of vanadium.
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Estimate the densities of argon and xenon by interpolation from the data.
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Provide an estimate of the density of the yet undiscovered element with atomic number 118 by extrapolation from the data.
In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cation-anion distances are 2.01 Å (Li - F), 2.82 Å (Na - Cl), 3.30 Å (K - Br), and 3.67 Å (Rb - I), respectively. What estimates of the cation-anion distance would you obtain for these four compounds using neutral atom bonding atomic radii?
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Use the molar mass of neon to estimate the mass of a neon atom.
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Use the densities and molar masses of krypton and neon to calculate the number of atoms of each found in a volume of 1.0 L.
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Use the atomic radius of neon to calculate the average density of a neon atom.
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 How does this density compare to the density of neon gas? What does this comparison suggest about the nature of neon gas?
Consider the densities and atomic radii of the following noble gases at 25 oC: Element Atomic Radius (pm) Density (g/L) He 32 0.18 Ne 70 0.90 Ar 98 - Kr 112 3.75 Xe 130 - Rn - 9.73 Use these values to estimate the number of atoms that occur in 1.0 L of Ar. Now use the molar mass of argon to estimate the density of Ar.
Consider S, Cl, and K and their most common ions.List the atoms in order of decreasing size.
Tungsten has the highest melting point of any metal in the periodic table: 3422 °C. The distance between W nuclei in tungsten metal is 2.74 Å.What is the atomic radius of a tungsten atom in this environment? (This radius is called the metallic radius.)
Estimate the As-I bond length from the data in the figure.
Trends in bonding atomic radii for periods 1 through 5.Which part of the periodic table has the elements with the largest atoms?
In Section 7.2 in the textbook we said that Zeff generally increases when you move down a column of the periodic table, whereas in Chapter 6 we saw that the "size" of an orbital increases as the principal quantum number n increases.With respect to atomic radii, do these trends work together or against each other?
In the series of group 5A hydrides, of general formula MH3, the measured bond distances are P-H, 1.419 Å; As-H, 1.519 Å; Sb-H, 1.707 Å.Compare these values with those estimated by use of the atomic radii in the figure.
In the series of group 5A hydrides, of general formula MH3, the measured bond distances are P-H, 1.419 Å; As-H, 1.519 Å; Sb-H, 1.707 Å.Explain the steady increase in M-H bond distance in this series in terms of the electron configurations of the M atoms.
Note from the following table that there is a significant increase in atomic radius upon moving from Y to La whereas the radii of Zr to Hf are the same. Suggest an explanation for this effect.
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
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
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
For each of the following pairs of elements:(C and N)     (Ar and Br)pick the atom with the larger size.
Hypothetical elements X and Y form a molecule XY2, in which both Y atoms are bonded to atom X (and not to one another). The X–X distance in the elemental form of X is 2.04 Y–Y and the Y distance in elemental Y is 1.68 Y–Y. What would you predict for the  m X!–!Y distance in the XY2 molecule?
For each of the following pairs of elements:(Mg and K)     (F and Cl)pick the atom with the larger size.
Using only the periodic table, arrange each set of atoms in order of decreasing radius.Na, Ba, and Ca:
Using only the periodic table, arrange each set of atoms in order of decreasing radius.As, In, and Sn:
Using only the periodic table, arrange each set of atoms in order of decreasing radius.Be, Al, and Si:
On the basis of periodic trends, choose the larger atom from each pair (if possible):(a) Sn or I(b) Ge or Po(c) Cr or W(d) F or Se
Name the element described in the following: Smallest atomic radius in Group 6A(16).
Name the element described in the following: Largest atomic radius in Period 6.
Name the element described in the following: Smallest metal in Period 3.
Arrange these elements in order of decreasing radius: S, Ca, F, Rb, and Si.
Name the element described in the following: Heaviest lanthanide.
Choose the larger atom from each pair.a. Sn or Sib. Br or Gac. Sn or Bid. Se or Sn
Arrange the following elements in order of decreasing atomic radius: Cs, Sb, S, Pb, and Se.
Which of the following pairs of elements would you expect to have the most similar atomic radii?a. Si and Gab. Si and Gec. Si and As
Hydrogen is an unusual element because it behaves in some ways like the alkali metal elements and in other ways like nonmetals. Its properties can be explained in part by its electron configuration and by the values for its ionization energy and electron affinity.Is the following statement true: “Hydrogen has the smallest bonding atomic radius of any element that forms chemical compounds.”? If not, correct it. If it is, explain in terms of electron configurations.
Consider the following elements: P, Ca, Si, S, Ga.Arrange the elements in order of decreasing atomic radius.
Arrange the following atoms in order of increasing size: Te, S, Se.
Arrange the following atoms in order of increasing size: K, Br, Ni.
Arrange the following atoms in order of increasing size: Ba, Si, F.
Arrange the following atoms in order of increasing size: Rb, Na, Be.
Arrange the following atoms in order of increasing size: Sr, Se, Ne.
Arrange the following atoms in order of increasing size: Fe, P, O.
You may want to reference (Pages 263 - 267) Section 7.3 while completing this problem.With the exception of helium, the noble gases condense to form solids when they are cooled sufficiently. At temperatures below 83 K, argon forms a close-packed solid whose structure is shown below.What is the apparent radius of an argon atom in solid argon, assuming the atoms touch as shown in this figure? Is this value larger or smaller than the bonding atomic radius estimated for argon in the figure shown below?
You may want to reference (Pages 263 - 267) Section 7.3 while completing this problem.Which of the following statements about the bonding atomic radii in the following figure is incorrect?(i) For a given period, the radii of the representative elements generally decrease from left to right across a period.(ii) The radii of the representative elements for the n = 3 period are all larger than those of the corresponding elements in the n = 2 period.(iii) For most of the representative elements, the change in radius from the n = 2 to the n = 3 period is greater than the change in radius from n = 3 to n = 4.(iv) The radii of the transition elements generally increase moving from left to right within a period.(v) The large radii of the Group 1A elements are due to their relatively small effective nuclear charges
You may want to reference (Pages 263 - 267) Section 7.3 while completing this problem.With the exception of helium, the noble gases condense to form solids when they are cooled sufficiently. At temperatures below 83 K, argon forms a close-packed solid whose structure is shown below.What is the apparent radius of an argon atom in solid argon, assuming the atoms touch as shown in this figure?
Which atom has the smaller radius: H or He?
You may want to reference (Pages 263 - 267) Section 7.3 while completing this problem.With the exception of helium, the noble gases condense to form solids when they are cooled sufficiently. At temperatures below 83 K, argon forms a close-packed solid whose structure is shown below.Compare the atomic radius of argon in the figure above and the bonding atomic radius estimated for argon in the figure shown below. Based on this comparison would you say that the atoms are held together by chemical bonds in solid argon?
Write the symbol for the element which has the smallest atomic radius.C, Si, Be, F.
Which atom has the smallest radius: Cl, In, or Se?
Which atom has the smallest radius: element 120, element 119, or element 116?
Which atom has the smallest radius: Nb, Zn, or Si?
In the table below, the bonding atomic radius of neon is listed as 0.58 Å, whereas that for xenon is listed as 1.40 Å. A classmate of yours states that the value for Xe is more realistic than the one for Ne.Is she correct? If so, what is the basis for her statement?
The following observations are made about two hypothetical elements A and B: The A–A and B–B bond lengths in the elemental forms of A and B are 2.36 and 1.94 Å, respectively. A and B react to form the binary compound AB2, which has a linear structure (that is ∠B–A–B = 180°). Based on these statements, predict the separation between the two B nuclei in a molecule of AB2.
Arrange each set in order of increasing atomic size:(a) Rb, K, Cs 
Based on their positions in the periodic table, predict which has the smallest atomic radius: Mg, Sr, Si, Cl, I.
Arrange each set in order of increasing atomic size:(b) C, O, Be
Arrange each set in order of increasing atomic size:(c) Cl, K, S
Based on their positions in the periodic table, predict which has the largest atomic radius: Li, Rb, N, F, I.
You may want to reference (Pages 263 - 267) Section 7.3 while completing this problem.Consider the A2X4 molecule depicted below, where A and X are elements. The A–A bond length in this molecule is d1exttip{d_{ m 1}}{d_1}, and the four A–X bond lengths are each d2exttip{d_{ m 2}}{d_2}.In terms of d1 exttip{d_{ m 1}}{d_1}and d2exttip{d_{ m 2}}{d_2}, how could you define the bonding atomic radius of atom A?
Arrange each set in order of increasing atomic size:(d) Mg, K, Ca
Consider the A2X4 molecule depicted below, where A and X are elements. The A- bond length in this molecule is exttip{d_{ m 1}}{d_1}, and the four A- bond lengths are each exttip{d_{ m 2}}{d_2}.In terms of exttip{d_{ m 1}}{d_1} and/or exttip{d_{ m 2}}{d_2}, how could you define the bonding atomic radius of atom X?
Arrange each set in order of decreasing atomic size:(a) Ge, Pb, Sn 
Arrange each set in order of decreasing atomic size:(b) Sn, Te, Sr
Arrange each set in order of decreasing atomic size:(c) F, Ne, Na 
An unknown element is a nonmetal and has a valence electron configuration of ns2 np4. Would this element have a larger or smaller radius than barium?
Arrange each set in order of decreasing atomic size:(d) Be, Mg, Na
Based on their positions in the periodic table, list the following atoms in order of increasing radius: Mg, Ca, Rb, Cs.
Based on their positions in the periodic table, list the following atoms in order of increasing radius: Sr, Ca, Si, Cl.
The experimental Bi-I bond length in bismuth triiodide, BiI3, is 2.81 Å. Based on this value and data in the figure, predict the atomic radius of Bi.
Using only the periodic table, arrange the following atoms in order from largest to smallest: K, Li, Cs.
Using only the periodic table, arrange the following atoms in order from largest to smallest: Pb, Sn, Si.
Using only the periodic table, arrange the following atoms in order from largest to smallest: F, O, N.
Before Mendeleev published his periodic table, German scientist Johann Döbereiner grouped elements with similar properties into “triads,” in which the unknown properties of one member could be predicted by averaging known values of the properties of the others. To test this idea, predict the values of the following quantities:(a) The atomic mass of K from the atomic masses of Na and Rb
The measured Bi-Br bond length in bismuth tribromide, BiBr3, is 2.63 Å. Based on this value and the data in the figure, predict the atomic radius of Bi m Bi.
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 
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
Which of these atoms has the smallest radius? (a) Al (B) P (C) As (D) Te (E) Na
Choose the larger atom from each of the following pairs.a. Al or Inb. Si or Nc. P or Pbd. Si or Cl
Rank the following atoms according to size: As, Cl, Se, F