For the d-block elements, the highest values occur for half-filled and near half-filled d orbitals. (W with a configuration of 5d6has the highest melting point.) Relating to Hund’s rule, it seems that metallic bonding strengthens as the number of unpaired electrons increases, reaching a maximum when the orbital is half-filled. Note that Hg and Rn have no unpaired electrons and substantially lower melting points. For the pblock elements (81–86), again the elements with unpaired p electrons tend to have higher melting points.
91. Define matter. Identify whether or not each of the following is a form of matter. a. microwaves no b. helium inside a balloon yes c. heat from the Sun no d. velocity no e. a speck of dust yes f. the color blue no Matter is anything that has mass and takes up space. 92. Convert the following mass measurements as indicated. 93. How is the energy of a quantum of emitted radiation related to the frequency of the radiation? The energy of a quantum equals the frequency times Planck’s constant. 94. What element has the ground-state electron configuration of [Ar]4s23d6? . iron 95. TriadsIn the early 1800s, German chemist J. W. Dobereiner proposed that some elements could be classified into sets of three, called triads. Research and write a report on Dobereiner’s triads. What element comprised the triads? How were the properties of elements within a triad similar? Dobereiner noticed that the atomic weight of strontium fell midway between the atomic weights of calcium and barium, elements that possessedsimilar chemical properties. He also studied the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad made up of lithium, sodium, and potassium. Dobereiner proposed that nature contained triads of elements in which the middle element (when ordered by atomic weight) had properties that were an average ofthe other two members. 96. AffinityElectron affinity is another periodic property of the elements. Write a report on what electron affinity is, and describe its group and period trends. Students will find that electron affinity (EA) is the energy change that accompanies one mole of electrons being added to one mole of gaseous atoms of ions. With many irregularities (and excluding the noble gases), first electron affinity (EA1) generally decreases from top to bottom within a group and increases from left to right within a period.Document-Based QuestionsMendeleev’s original periodic table is remarkable given the knowledge of elements at that time, and yet it is quite different from the modern version. Compare Mendeleev’s table, shown below, with the modern periodic table.
97. Mendeleev placed the noble gases on the left of his table. Why does placement on the right of the modern table make more sense? Placing them on the right has the representative elements ordered from left to right as orbitals of the energy levels are
- Fall '08