(c) Give the four quantum numbers for the valence electron in aluminium and explain the significance of each.

Use the data from Appendix F to graph the variation ofatomic radius with atomic number for the rare-earth elements from lanthanum to lutetium.(a) What is the general trend in these radii? How do you     account for it?(b) Which two elements in the series present exceptions to      the trend?

Which of the following has the smallest ionic radius? (A) p3- (B) K1+ (C) Sc3+ (D) Ar 7.

When a nonmetal oxide reacts with water, it forms an oxoacid with the same oxidation number as the nonmetal. Give the name and formula of the oxide used to prepare each of these oxoacids: (a) hypochlorous acid; (b) chlorous acid; (c) chloric acid; (d) perchloric acid; (e) sulfuric acid; (f ) sulfurous acid; (g) nitric acid; (h) nitrous acid; (i) carbonic acid; ( j) phosphoric acid.

Which element in each of the following sets would you expect to have the lowest third ionization energy, IE3? (a) O Na O Al O Mg (b) O Ga ок O Mg (c) O Ca O Sc OK ооо

The electron configuration of an element describes how electrons are distributed in its atomic orbitals. (a) Explain the applications of the Aufbau principle, Hund's rule and the Pauli exclusion principle in relation to electronic configuration of oxygen atom. Explain how these principles determine the stability and reactivity of atoms oxygen.

Boron, atomic number 5, occurs naturally as two isotopes, 10B and 11B, with natural abundances of 19.9% and 80.1%, respectively.(a) In what ways do the two isotopes differ from each other? Does the electronic configuration of 10B differ from that of 11B? (b) Drawthe orbital diagram for an atom of 11B. Which electrons are the valence electrons? (c) Indicate three ways in which the 1s electrons inboron differ from its 2s electrons. (d) Elemental boron reacts with fluorine to form BF3, a gas. Write a balanced chemical equation forthe reaction of solid boron with fluorine gas. (e) ΔHf° for BF31g2 is -1135.6 kJ>mol. Calculate the standard enthalpy change in thereaction of boron with fluorine. (f) Will the mass percentage of F be the same in 10BF3 and 11BF3? If not, why is that the case?

Despite the expected decrease in atomic size, there is an un-expected drop in the first ionization energy between Groups2A(2) and 3A(13) in Periods 2 through 4. Explain this pattern interms of electron configurations and orbital energies.

Valence electrons in an atom of phosphorus are closer to the nucleus than the valence electrons ofaluminum because: (A) P has a greater effective nuclear charge and a greater shielding than Al.(B) P has a greater effective nuclear charge with the same shielding as Al.(C) P has the same effective nuclear charge with greater shielding than Al.(D) P has the same effective nuclear charge and the same shielding as Al.

(a) Account for formation of the following series of oxidesin terms of the electron configurations of the elementsand the discussion of ionic K2O, CaO, Sc2O3, TiO2, V2O5, CrO3. (b) Name these oxides.(c) Consider the metal oxides whose enthalpies of formation(in kJ mol -1) are listed here. Calculate the enthalpy changes in the following general reactionfor each case:MnOm(s) + H2(g)----->nM(s) + mH2O(g)(You will need to write the balanced equation for each caseand then compute ΔH°.) (d) Based on the data given, estimatea value of ΔHf° for Sc2O3(s).