Periodic Patterns in the Main-Group Elements

Understand These Concepts Note: Many characteristic reactions appear in the “Reactions” section of each group's Family Portrait. 1. How hydrogen is similar to, yet different from, alkali metals and halogens; the differences between ionic, covalent, and metallic hydrides (§14.1) 2. Key horizontal trends in atomic properties, types of bonding, oxide acid-base properties, and redox behavior as the elements change from metals to nonmetals (§14.2) 3. How small atomic size and limited number of valence orbitals account for the anomalous behavior of the Period 2 member of each group (§14.2) 4. How the ns1 configuration accounts for the physical and chemical properties of the alkali metals (§14.3) 5. How the ns2 configuration accounts for the key differences between Groups 1A(1) and 2A(2) (§14.4) 6. The basis of the three important diagonal relationships (Li/Mg, Be/Al, B/Si) (§14.4–14.6) 7. How the presence of inner (n – 1)d electrons affects properties in Group 3A(13) (§14.5) 8. Patterns among larger members of Groups 3A(13) to 6A(16): two common oxidation states (inert-pair effect), lower state more important down the group, and more basic lower oxide (§14.5–14.8) 9. How boron attains an octet of electrons (§14.5) 10. The effect of bonding on the physical behavior of Groups 4A(14) to 6A(16) (§14.6–14.8) 11. Allotropism in carbon, phosphorus, and sulfur (§14.6–14.8) 12. How atomic properties lead to catenation and multiple bonds in organic compounds (§14.6) 13. Structures and properties of the silicates and silicones (§14.6) 14. Patterns of behavior among hydrides and halides of Groups 5A(15) and 6A(16) (§14.7, 14.8) 15. The meaning of disproportionation (§14.7) 16. Structure and chemistry of the nitrogen oxides and oxoacids (§14.7) 17. Structure and chemistry of the phosphorus oxides and oxoacids (§14.7) 18. Dehydration-condensation reactions and polyphosphate structures (§14.7) 19. Structure and chemistry of the sulfur oxides and oxoacids (§14.8) 20. How the ns2np5 configuration accounts for halogen reactivity with metals (§14.9) 21. Why the oxidation states of an element change by two units (§14.9) 22. Structure and chemistry of the halogen oxides and oxoacids (§14.9) 23. How the ns2np6 configuration accounts for the relative inertness of the noble gases (§14.10)

1 Hydrogen has only one proton, but its IE1 is much greater than that of lithium, which has three protons. Explain.

2 Complete and balance the following equations: a. An active metal reacting with acid,

b. A saltlike (alkali metal) hydride reacting with water,

14.8 Unlike the F– ion, which has an ionic radius close to 133 pm in all alkali metal fluorides, the ionic radius of H–varies from 137 pm in LiH to 152 pm in CsH. Suggest an explanation for the large variability in the size of H– but not F–.

14.18 Each of the following properties shows a regular trend in Group 1A(1). Predict whether each increases or decreases down the group: a. density;

b. ionic size;

c. E—E bond energy;

d. IE1; + e. magnitude of ΔHhydr of E ion. 14.23 Lithium forms several useful organolithium compounds. Calculate the mass percent of Li in the following: a. Lithium stearate (C17H35COOLi), a water-resistant grease used in cars because it does not harden at cold temperatures

b. Butyllithium (LiC4H9), a reagent in organic syntheses

How do Groups 1A(1) and 2A(2) compare with respect to reaction of the metals with water?

14.25 Alkaline earth metals are involved in two key diagonal relationships in the periodic table. a. Give the two pairs of elements in these diagonal relationships.

b. For each pair, cite two similarities that demonstrate the relationship.

c. Why are the members of each pair so similar in behavior? 14.30 In some reactions, Be behaves like a typical alkaline earth metal; in others, it does not. Complete and balance the following: a. BeO(s) + H2O(l)

− b. BeCl2(l) + Cl (l; from molten NaCl)

In which reaction does Be behave like the other Group 2A(2) members?

14.33 Despite the expected decrease in atomic size, there is an unexpected drop in the first ionization energy between Groups 2A(2) and 3A(13) in Periods 2 through 4. Explain this pattern in terms of electron configurations and orbital energies.

14.35 Boron's chemistry is not typical of its group. a. Cite three ways in which boron and its compounds differ significantly from the other 3A(13) members and their compounds.

b. What is the reason for these differences? 14.36 Rank the following oxides in order of increasing aqueous acidity: Ga2O3, Al2O3, In2O3.

14.41 Indium (In) reacts with HCl to form a diamagnetic solid with the formula InCl2. a. Write condensed electron configurations for In, In+, In2+, and In3+.

b. Which of these species is (are) diamagnetic and which paramagnetic?

c. What is the apparent oxidation state of In in InCl2?

d. Given your answers to parts (b) and (c), explain how InCl2 can be diamagnetic.

14.47 Give explanations for the large drops in melting point from C to Si and from Ge to Sn.

14.48 What is an allotrope? Name two Group 4A(14) elements that exhibit allotropism, and identify two of their allotropes. 4.54 Give the name and symbol or formula of a Group 4A(14) element or compound that fits each description or use: a. Hardest known natural substance

b. Medicinal antacid

c. Atmospheric gas implicated in the greenhouse effect

d. Gas that binds to Fe(II) in blood

e. Element used in the manufacture of computer chips

14.56 Which Group 5A(15) elements form trihalides? Pentahalides? Explain.

14.57 As you move down Group 5A(15), the melting points of the elements increase and then decrease. Explain. 14.58 a. What is the range of oxidation states shown by the elements of Group 5A(15) as you move down the group?

b. How does this range illustrate the general rule for the range of oxidation states in groups on the right side of the periodic table?

4.60 Rank the following oxides in order of increasing acidity in water: Sb2O3, Bi2O3, P4O10, Sb2O5.

14.74 Rank the following in order of increasing electrical conductivity, and explain your ranking: Po, S, Se.

14.75 The oxygen and nitrogen families have some obvious similarities and differences. a. State two general physical similarities between Group 5A(15) and 6A(16) elements.

b. State two general chemical similarities between Group 5A(15) and 6A(16) elements.

c. State two chemical similarities between P and S.

d. State two physical similarities between N and O. e. State two chemical differences between N and O. 14.79 Is each oxide basic, acidic, or amphoteric in water: (a) SeO2; (b) N2O3; (c) K2O; (d) BeO; (e) BaO?

14.81 Rank the following hydrides in order of increasing acid strength: H2S, H2O, H2Te.

14.87 a. Give the physical state and color of each halogen at STP.

b. Explain the change in physical state down Group 7A(17) in terms of molecular properties.

14.90 Select the stronger bond in each pair: a. Cl—Cl or Br—Br

b. Br—Br or I—I

c. F—F or Cl—Cl.

d. Why doesn't the F—F bond strength follow the group trend?

14.95 Rank the following acids in order of increasing acid strength: HClO, HClO2, HBrO, HIO. 14.100 Which noble gas is the most abundant in the universe? In Earth's atmosphere?

14.107 The electronic transition in Na from 3p1 to 3s1 gives rise to a bright yellow-orange emission at 589.2 nm. What is the energy of this transition?

14.115 All common plant fertilizers contain nitrogen compounds. Determine the mass % of N in a. ammonia;

b. ammonium nitrate;

c. ammonium hydrogen phosphate.