Periodic Properties

Chapter 7

Periodic PropertiesPeriodic Properties –depend on element’s position on table

Ex: GroupsH, Li, & Na all form similar oxides(H2O, Li2O, Na2O)

Location gives you A LOT of information

2 Main Factors for Periodic Properties1. Number of Levels – More levels, electrons

held less tightly1. More shielding2. More electron to electron repulsion (PUSH)

2. Number of Protons – More protons hold electrons more tightly. Greater effective nuclear charge (Zeff) (PULL)

Periodic Properties

Properties we will study:1. Size of Atoms2. Size of Ions3. Ionization Energy4. Multiple Ionization Energy5. Electron Affinity

Periodic Properties

Size of AtomsAtomic Radius

1. Measured in picometers (1pm = 1 X 10-12 m) or

Angstroms (1 Å = 100 pm)2. Average radius ~100 pm (1 Å)

Size of Atoms3. Example: Bromine 1.14 Å

1.14 Å X 100 pm = 114 pm1 Å

Effective Nuclear ChargeZeff = Z-S

Z = # protonsS = # core electron

What is the Zeff for chlorine (1s22s22p63s23p5)?

Zeff = Z-S

Zeff = 17- 10 = 7+

Size of AtomsDown a group

– Atoms get larger (more levels)– Shielding Effect – Core electrons shield the pull of the

nucleus (more electron repulsion) (PUSH wins)

H 1 level Zeff = 1+

Li 2 levels Zeff = 1+

Na 3 levels Zeff = 1+

Size of Atoms

Size of Atoms

Across a period – atoms get smaller (same level), greater Zeff (PULL wins)

Li FE configLevelsZeff

Size of AtomsSi Cl

Size of Ions

A. Positive Ions1. Example:

Mg Mg+

E configLevelsZeff

Size of Ions

Size of IonsPositive ions always smaller

– Fewer electrons to control– Less e- to e- repulsion

Mg Mg+ Mg2+

E configLevelsZeff

Size of Ions

B. Negative Ions1. Example:

O O2- O3-

E configLevelsZeff

Size of Ions

Size of IonsNegative ions always larger

– More electrons to control– More e- to e- repulsion

More levels

Greater Zeff

(same levels, greater Zeff smaller)

IonsPositive = smaller(less electron repulsion)

Negative = Larger (more electron repulsion)

If same

If same

Size Review

Which is larger and why?Li or K

S or S2+

Mg or S

O or Te

Size ReviewKurveballK or K+

Ionization EnergyA.Ionization energy – The energy needed to remove

an electron from an isolated gaseous atom or ion

Na Na+ + e-

He

Ne

Ar

KLi Na

H

A low energy photon will excite an electron

BOHR MODEL

A high energy photon may ionize an atom (completely remove the electron)

PHOTOELECTRIC EFFECT

Ionization Energy

B. Ionization energy is inversely proportional to atomic radius

Examples: Li (520 kJ/mol) F (1681)Na (496 kJ/mol) Cl (1251)

Ionization Energy

Which has the higher Ionization Energy and why?C or O

Na or Cl

C or Sn

Mg or Ra

Multiple Ionization Energy

Multiple Ionizations - Removing more than one electron1st Mg Mg+ + e- 738 kJ/mol2nd Mg+ Mg2+ + e- 1450 kJ/mol3rd Mg2+ Mg3+ + e- 7732 kJ/mol

There is a large jump once you reach Noble Gas

Configuration (Fewer levels, spike in Zeff)

Multiple Ionization Energy

Multiple Ionization Energy

1st Al Al + + e- 577 kJ/mol2nd Al + Al 2+ + e- 1816 kJ/mol3rd Al 2+ Al 3+ + e- 2744 kJ/mol 4th Al3+ Al4+ + e- 11580 kJ/mol

Multiple Ionization Energy

Examples:a. Where will the large jump in I.E. occur for:

Be B P

b. Element X has a large jump between its 4th and 5th I.E. To what group does it

belong?

Electron Affinity• Energy change that occurs when an electron is

added to an isolated gaseous atom or ion• Ease with which an atom gains an electron• Cl(g) + e- Cl-(g) E = -349 kJ/mol• Positive for noble gases (don’t want electrons)

Properties of Metals• Malleable and ductile• Good conductors• Large radius/Low ionization energy• Form positive ions (+2 and +3 for transition

metals)

Metal Oxides• Most metals oxidize easily in the atmosphere

2Ni(s) + O2(g) 2NiO(s)• Metal oxides are bases

Metal Oxide + Water Metal hydroxide (base)Na2O(s) + H2O(l) 2NaOH(aq) CaO(s) + H2O(l) Ca(OH)2(aq)

Metal Oxide + Acid Salt + WaterMgO(s) + HCl(aq) MgCl2(aq) + H2O(l)

NiO(s) + H2SO4(aq) NiSO4(aq) + H2O(l)

Al(s) + O2(g)

Zn(s) + O2(g)

CaO(s) + H2O(l)

Li2O(s) + H2O(l)

Al2O3(s) + HNO3(aq)

CuO(s) + H2SO4(aq)

Properties of Non-Metals• Dull• Poor conductors• Solids, liquids and gases• Non-metal oxides are acidic

Non-metal ReactionsCombination Reactions

2Al(s) + 3Br2(l) 2AlBr3(s)

Non-Metal Oxide + Water AcidCO2(g) + H2O(l) H2CO3(aq)

P4O10(s) + 6H2O(l) 4H3PO4(aq)

Non-Metal Oxide + Base Salt + WaterCO2(g) + 2NaOH(aq) Na2CO3(aq) + H2O(l)

SO3(s) + 2KOH(l) K2SO4(aq) + H2O(l)

Predict the products in the following reactions:

Ba(s) + S8(g)

Ga(s) + Se(g)

SO2(s) + H2O(l)

SeO2(s) + 2NaOH(l)

SO3(s) + H2O(l) (acid rain reaction)

Group Names

Trends: Alkali Metals• Soft, reactive (M M+ + e-)Reactions with water

Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

Reactions with hydrogen (less electronegative than hydrogen)2Na(s) + H2(g) 2NaH(s)[H-, hydride ion]

Reactions of Na and K with oxygen (exceptions)2Na(s) + O2(g) Na2O2(s) [peroxide]

K(s) + O2(g) KO2(s) [superoxide]

Trends: Alkaline Earth Metals• Become more reactive as you go down the table

(just like alkali metals)• 99% of calcium in the body is in the skeleton

Trends: Transition and Post-Transition Metals

• Often +2 and +3 ions• Pt and Au are fairly unreactive

Trends: Hydrogen

• Non-metal• Forms hydrides (H-) with alkali and alkaline earth

metals2Na(s) + H2(g) 2NaH(s)

Ca(s) + H2(g) CaH2(s)

Trends: Chalcogens

• Ozone = O3 (between 10-50 km in the atmosphere, allotrope of oxygen)

• Hydrogen peroxide2H2O2(aq) 2H2O(l) + O2(g)

-good oxidizing agent/disinfectant-Can be decomposed by light

Trends: Halogens

• “Salt formers”• Reactivity decreases down the table• Fluorine is most reactive• Chlorine as a bleaching agent

Cl2(g) + H2O(l) HCl + HOCl (bleach)

NaOCl (Clorox)Ca(OCl)2 (swimming pool bleach)

Noble Gases•Some do react•XeF4 shown below

8. Tc12.a) Effective nuclear charge is decreased by

core electronsb) 1s is less shielded

22. 1.33 Angstroms26.a) Na<Ca<Ba b) As<Sb<Sn

c) Be<Si<Al28.a) Z = Constant, e- repulsion increases (I-

>I>I+)b) Z = Constant, e- repulsion increases (Ca2+

> Mg2+>Be2+ )c) Fe>Fe2+>Fe3+

30 Ca = Largest, Ca2+ middle, Mg2+ smallest

32. a) Cl-, Ar b) Sc3+, Ar c) Fe2+, noned) Zn2+, none e) Sn4+, none

34 a) K+ smaller b) Zeff = +7(Cl-) and +9(K+)

36 a) Se <Se2-<Te2- b) Co3+<Fe3+<Fe2+

c) Ti4+<Sc3+<Ca d) Be2+<Na+<Ne38. LiCl (2.09 ionic, 2.05 covalent)

NaCl (2.83 ionic, 2.53 covalent)KBr (3.34 ionic, 3.10 covalent)RbI (3.72 ionic, 3.44 covalent)

40. Sn Sn+ + e- Sn+ Sn2+ + e-

Ti3+ Ti4+ + e-

42. a) Li smaller, higher IE b) Sc higher b/c NGCc) Li+ is higher b/c NGC

44. a) Inversely proportional b) same explanation46.a) Ti b) Cu c) Cl d) Sb48.a) [Ar]3d3 b) [He]2s22p6

c) [Ne]3s23p6 d) [Ar]3d9

e) [Xe]6s24f145d10 e) [Xe]4f145d10 74. 2Cs + 2H2O 2CsOH + H2

Sr + 2H2O Sr(OH)2 + H2

2Na + O2 Na2O2

Ca + I2 CaI2

68.K2O + H2O 2KOH

P2O3 + 3H2O 2H3PO3

Cr2O3 + 6HCl 2CrCl3 + 3H2O

SeO2 + 2KOH H2O + K2SeO3

74.2Cs + 2H2O 2CsOH + H2

Sr + 2H2O Sr(OH)2 + H2

2Na + O2 Na2O2

Ca + I2 CaI2

82.Cl2 + H2O HOCl + HCl Ba + H2 BaH2

2Li + S Li2S F2 + Mg MgF2

a. Rank the following according to size (smallest to largest)

Be F F- O2- O Be2+

b. Why is Be3+ difficult to produce?c. Which factor is most important in

explaining the size of the O2- ion compared to the O atom: Zeff or mutual electron repulsion?

d. Which factor is most important in explaining the size of the P atom compared to the Cl atom: Zeff or mutual electron repulsion?

a. Rank the following according to size (smallest to largest)

S2- K+ Ca2+ Cl-

b. Rank the following in order of increasing first ionization energy: Ne, Na, P, Ar, K

c. Write the electron configuration for:Co3+ S2- Fe2+

d. Would you expect an acidic, basic or neutral pH if Li2O is placed in water? CO2?

SO2(s) + 2NaOH(l)

Cu(s) + O2(g)

Ba(s) + H2(g)

SeO3(s) + H2O(l)

Al(s) + F2(g)

Ca(s) + O2(g)

CO2(s) + H2O(l)

CaO(s) + H2O(l)

K2O(s) + H2O(l)

CO2(s) + 2NaOH(l)

Al2O3(s) + HCl(g)

Ga(s) + Te(g) SO2(s) + H2O(g)

Li(s) + H2O(l)

Na(s) + O2(g)

Ca(s) + S8(g)

1. Make up a compound containing 3 elements1. No subscripts >52. Use both even and odd numbers3. Ex: C3O5F2

2. Calculate the percent composition of your imaginary compound. Write it down on an index card.

3. Give your card to another group. See if they can determine the formula of your compound.