Periodicity Review Worksheet
1. Which atom in the following pairs would have the larger atomic radii?
P or Cl
K or Mg
As or Se
Si or O
P or Ge
Sn or Pb
Cl or Br
Ca or Al
Mg or Ca
Sn or As
Si or S
H or He
Na or Mg
Al or Cl
Sr or Ra
2.Which ion in the following pairs would have the larger radii?
Li+ or Be2+
Cr3+ or Cr6+
S2- or O2-
Mg2+ or Be2+
Na+ or Al3+
I- or Cl-
Cs+ or Be2+
Zn2+ or Fe2+
P3- or S2-
Cu+ or Cu2+
N3- or F-
3.Which member of the following pairs would have a larger radii?
Br or BrCa or Ca2+
S or S6+
Al or Al3+
O or O2Li or Li+
P or P3N3- or Al3+
4.Which atom in the following pairs would have the greater first ionization energy?
Sr or Ba
Cs or Ba
Cl or Ar
In or Sn
Xe or Kr
Mg or Sr
Ca or Cu
5. What is the difference between electron affinity and ionization energy?
Electron affinity is the energy released when an atom gains an electron whereas ionization
energy is the energy needed to remove an electron.
6. Which member in the following pairs would have the greater electron affinity &
electronegativity?
F or Cl
S or O
F or O
N or O
F or Any element S or Cl
Nonmetal or Metal
Ca or K
C or O
Ca or F
Mg or Na
Al or Si
Na or K
7. What is the difference between a cation and an anion?
A cation is a positively charged ion. It forms when an atom loses electron(s). An anion is a
negatively charged ion. It forms when an atom gains electron(s).
8. Identify three anions in Period 2 that can have the same number of electrons when they
become ions. Do they gain or lose electrons? F-, O2-, N39. Identify three cations in Period 3 that can have the same number of electrons when they
become ions. Do they gain or lose electrons? Na+ , Mg2+, Al3+
10. Identify the ions that are most likely to have an ion charge (oxidation state) of 2-? (Hint:
there are five of them) O2-, S2-. Se2-, Te2-, Po211. Identify the ions that are most likely to have an ion charge (oxidation state) of 2+? (Hint:
there are six of them) Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+
12. Why do elements in the same family generally have similar properties?
They all have the same number of valence electrons (electrons in their highest energy level s
and p orbitals).
13. Which element has the greatest electron affinity? Why?
Fluorine, because it has the smallest atomic radius and only needs one more electron to
be isoelectronic with a noble gas.
14. Which element has the lowest ionization energy? Why?
Francium, because it has the largest atomic radius and only needs to lose one electron to be
isoelectronic with a noble gas.
15. Consider all elements in period 3 for the following (Na through Ar)
_Na___ has the largest atomic radius
_Cl___ has the greatest electron affinity
_Ar___ has the highest first ionization energy
_Na___ is the most reactive metal
_Cl___ is the most reactive non metal
_Ar___ is the least reactive
_Si_______ are metalloids
_Na, Mg, Al__________ are most likely to be cations
_P, S, Cl____________are most likely to be anions
_Al____loses 3 electrons to have noble gas configuration (isoelectronic to the noble gas)
_P____ gains 3 electrons to have noble gas configuration (isoelectronic to the noble gas)
16. Consider all elements in group 17 (O through Po)
_Po___ is the least reactive
_O___ is the most reactive
_O___ has the greatest electron affinity
_O___ has the greatest first ionization energy
_O___ has the smallest atomic radius
17. In a given period, are cations larger or are anions bigger?
Anions are bigger
18. Is the radius of a cation larger or smaller than the neutral atom? Why?
Smaller, because it is losing electrons.
19. Is the radius of an anion larger or smaller than the neutral atom? Why?
Larger, because it is gaining electrons.