Chemical Periodicity Chart

Practice ProblemQuestions and Answers

Atomic Radius

• P. 178 #16, 22• 16: How does atomic size change within

groups and across periods?– Increases down the groups, decreases left-to-right

across periods.• 22: Arrange in order of decreasing size: S, Cl,

Al, Na. Is there a pattern?– Na, Al, S, Cl– This is a period-based trend (left-to-right, n=3).

Atomic Radius

• P.181 #36– A: Which element has a larger radius: Na or Li?• Na

– B: Which element has a larger radius: Sr or Mg?• Sr

– C: Which element has a larger radius: C or Ge?• Ge

– D: Which element has a larger radius: O or Se?• Se

Atomic Radius

• P. 182 #50• Why does fluorine have a smaller atomic

radius than oxygen and chlorine?– It’s further to the right in oxygen’s period, it’s

higher up than chlorine.– In other words, “stronger nucleus” than oxygen,

fewer electrons than chlorine.

Ionization Energy

• P. 178 #17-18• 17: When do ions form?– When electrons are added or removed.

• 18: What happens to first ionization energy within groups and across periods?– Increases left-to-right across periods, decreases

down groups.

Ionization Energy

• P.178 #23• A: Which element has the larger first

ionization energy: Na, K?– Na

• B: Which element has the larger first ionization energy: Mg, P?– P

Ionization Energy

• P.181 #37, 38• 37: Explain the difference between first and second

ionization energy:– First i.e. = energy to remove one electron.– Second i.e. = energy to remove a second electron

• 38: Which element has a greater first i.e.?– Li, B

• B

– Mg, Sr• Mg

– Cs, Al• Al

Ionization Energy

• P. 181 #39• Arrange the groups of elements in order of

increasing ionization energy:– Be, Mg, Sr• Sr, Mg, Be

– Bi, Cs, Ba• Cs, Ba, Bi

– Na, Al, S• Na, Al, S

Ionization Energy

• P.181 #40• Why is there a large increase between the first

and second ionization energies of the alkali metals?– After removing the first electron, the second

electron is in a lower (closer) energy level (lower n number).

Ionization Energy

• P. 182: 51, 55• 51: Would you expect metals or nonmetals in the

same period to have higher i.e.?– Nonmetals – they’re further right (“stronger nuclei”)

• 55: Which equation represents the first ionization of an alkali metal atom?– A: Cl Cl+ + e-

– B: Ca Ca+ + e-

– C: K K+ + e-

– D: H H+ + e-

Ionization Energy

• P. 182: 51, 55• 51: Would you expect metals or nonmetals in the

same period to have higher i.e.?– Nonmetals – they’re further right (“stronger nuclei”)

• 55: Which equation represents the first ionization of an alkali metal atom?– A: Cl Cl+ + e-

– B: Ca Ca+ + e-

– C: K K+ + e-

– D: H H+ + e-

Ionization Energy

• P.182 #58• Why is there a large jump between the second

and third ionization energies of magnesium? Why is there a large jump between the third and fourth ionization energies of aluminum?– Those last electrons are in closer energy shells

(lower n number).

Ionic Size

• P. 178 #19• Compare the size of ions to the size of their

neutral forms.– Cations lose electrons, become positively charged,

get smaller.– Anions gain electrons, become negatively charged,

get larger.

Ionic Size

• P. 181 #41, 42• 41: How does the ionic radius of a typical metal compare with

its atomic radius?– Metals tend to lose electrons so their ionic radii get smaller.

• 42: Which particle has a larger radius in each atom/ion pair?– Na, Na+

• Na

– S, S2-

• S2-

– I, I-

• I-

– Al, Al3-

• Al

Ionic Size

• P. 182: #52• In each pair, which ion is larger?– Ca2+, Mg2+

• Ca2+

– Cl-, P3-

• P3-

– Cu+, Cu2+

• Cu+

Ionic Size

• P. 182 #59• The bar graph shows the relationship between

atomic and ionic radii for Group 1A elements. A: Describe the trend in atomic radius. B: Explain the difference between ionic and atomic radius size?– A: Radius increases as you go down a group.– B: Ions are smaller due to fewer electrons than in

the neutral atom (atomic radius).

Ionic Size

• P.183 #64, 65• 64: The Mg2+ and Na+ ions each have ten electrons.

Which is smaller and why?– Mg2+ is smaller because though it has ten electrons just like

Na+, it has more protons. They pull “harder” on the electrons.• 65: How do you expect the radii of S2-, Cl-, K+, Ca2+, and

Sc3+ to vary – they have the same total electrons as the noble gas Argon. What about for O2-, F-, Na+, Mg2+, and Al3+, which is the same as Neon?– Radius decreases from left to right across a period in both

cases. Though electron # is the same, proton number goes up.

Ionic Size

• P. 183 #68• Atoms and ions with the same number of

electrons are isoelectronic.– Write the symbol for a cation and anion that are

isoelectronic with Krypton:• Br-, Rb+, Se2-, As3-, Sr2+ (each have 36 electrons)

– Can you have an isoelectric cation and anion in the same period?• No, cations lose electrons but anions (higher overall

number of electrons) gain them.

Electronegativity

• P. 178 #20• How does electronegativity vary within groups

and across periods?– Increases across period left-to-right.– Decreases down groups.

Electronegativity

• P.181 #43• A: Which element has a higher electronegativity value: Cl, F?

– F• B: Which element has a higher electronegativity value: C, N?

– N• C: Which element has a higher electronegativity value: Mg,

Ne?– Mg [Ne does not react]

• D: Which element has a higher electronegativity value: As, Ca?– As

Electronegativity

• P.181 #44• Why are noble gases not given

electronegativity values?– Electronegativity only applies in compounds.

Noble gases don’t react and form compounds.