GENERAL CHEMISTRY. YUFIDANI L2C yuffidhani.wordpress.com

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1 GENERAL CHEMISTRY YUFIDANI L2C00908 yuffidhani.wordpress.com. The radii of the sodium and potassium ions are 02 pm and 38 pm, respectively. Which compound has stronger ionic attractions, sodium chloride or potassium chloride? Answer : The energy of attraction (or repulsion) between two particles is directly to the product of the charge and inversely proportional to the distance between them. charg e charg e2 We have equation Energy dis tan ce Smaller ion attracts each other ion more strongly than larger ions, because their charges are closer together. Sodium is smaller than potassium, so sodium chloride(nacl) has stronger ionic attraction than potassium chloride(kcl). 2. Does potassium nitrate (KNO 3 ) incorporate ionic bonding, covalent bonding, or both? Explain Answer : KNO 3 K + NO 3 The anion NO 3 (nitrate) is polyatomic ion, which consist of four covalently bonded atoms. NO 3 incorporate covalent bonding because the elements of nitrate share electrons. And then ionic bonding occurred between K (as cation) and NO 3 (as anion). Potassium atom losses electron and forms a potassium cation (K ), and nitrate gains an electron and becomes a nitrate anion (NO 3 ). So KNO 3 incorporate both ( ionic bonding and covalent bonding). 3. An X-ray has a wavelength of,3, calculate the energy (in joule) of one photon of this radiation? Answer : E = nhv = nh c = () ( 6,626 x 0-34 J.s) =,529 x 0-5 joule (3 (,3 8 0 m ) s 0 0 m)

2 4. The following quantum number combinations are not allowed, assuming the n and ml values are correct. Chance the l value to create an allowable combination a. n = 3 l = 0 ml = - b. n = 3 l = 3 ml = + c. n = 7 l = 2 ml = +3 d. n = 4 l = ml = -2 Answer : The orbital filling order s 2s 2p 3s 3p 3d 4s 4p 4f 5p 5d 5f 6s 6p 6d 7s 7p a. n = 3 l = 0 ml = If the l value is 0, it s false, because l=0 has configuration 3s, as we know that s just has one orbital, in fact ml=- minimal has three orbitals(3p), so we can create l value is (l = ). b. n = 3 l = 3 ml = If the l value is 3, it s mean that the electron 3f, and it s false, because in electron filling order 3f is nothing. If ml = +2, the electron must be 3p. So we can create l value is 2 (l = 2). c. n = 7 2

3 l = 2 ml = If the l value is 2, it s mean that the electron 7d, and it s false, because nothing 7d. And the biggest possibility is 7p, but the ml value also must be changed becomes ml = +. So we can create l value is (l = ). d. n = 4 l = ml= If the l value is, it s false, because l= has configuration 4p, as we know that p has three orbitals, in fact ml=-2 has five orbitals, so we can create l value is 2 (l = 2) 5. Write a full set of quantum number for the following: a. outermost electron in an Rb atom b. the electron gained when an S - ion becomes an S 2- ion c. the electron lost when an Ag atom iones d. the electron gained when an F - ion forms from an F atom Answer : a. 37 Rb e = 37 [Kr] n = 5 l = 0 m = 0 s = + 2 b. 6 S 2 e = 8 [Ne] 3s 2 3p 6 n = 3 l = m = s = - 2 c. Ag Ag + e 47Ag e = 46 [Kr] 2 8 n = 4 l = 2 m = 0 s = - 2 3

4 d. F + e F e = 0 9 F s 2 2s 2 2p 6 n = 2 l = m = s = Palladium (Pd, Z=46) is diamagnetic. Draw partial orbital diagram to show which of the following electron configurations is consistent with this fact: a. [Kr] 2 8 b. [Kr] 0 c. [Kr] 9 Answer : a. [Kr] 2 8 b. [Kr] 0 c. [Kr] 9 Palladium is diamagnetic. Diamagnetic is a species with all electrons paired. So the electron configuration that consistent with this fact is [Kr] 0. 4

5 7. Both nitrogen and bismuth are members of group 5A. Which is more metallic? Explain your answer in term of atomic properties Answer : INCREASES METALLIC BEHAVIOR N Bi Metallic behavior decreases left to right and increases top to bottom in the periodic table. Metals tend to lose electrons during chemical reactions because they have low ionizations energies. As we move across a period, it becomes more difficult to lose an electron because of ionization energies (IE) increases and easier to gain electron (electron affinities/ea becomes more negative). So, it s means that Bismuth more metallic than Nitrogen. 8. When liquid benzene (C 6 H 6 ) boils, does the gas consist of molecules, ions, or separates atoms? Explain scientifically Answer : Benzene consist of six atoms of carbon and six atoms of hydrogen that bonded circle pattern (sickles). Benzene including aromatic compounds. Benzene has molecule structure like this Symmetries structure shows six atoms of carbon on benzene, and circle in the center shows crowd of aromatic on benzene molecule. Crowd of aromatic is contained by six electrons from p orbital. This process is electron delocalization. Crowd of electron is the main character of aromatic compound and makes benzene molecule more stabile. So, when liquid benzene boils, the gas consists of molecules. 5