General Chemistry

Give the electron configuration of a ground state Zn2+ ion. A. [Ar] 4s23d8 B. [Ar] 3d10 C. [Ar] 4s13d9 D. [Ar] 4s23d10

Answer B First, eliminate choices that involve the wrong number of electrons. Since an atom of zinc contains 30 electrons, a Zn2+ ion contains 28, eliminating [Ar] 4s23d10. Recall that when electrons are removed from a transition metal such as zinc, the electrons always come from the valence s orbital first. Therefore, the electron configuration, [Ar] 3d10 is the correct one.

Which of the following appropriately ranks the atoms from smallest to largest atomic radius? A. Ge < Al < P < C B. C < P < Al < Ge C. C < Al < P < Ge D. Ge < P < Al < C

Answer B This is a ranking question, which is best approached by evaluating the extremes. For a given family, atomic radius increases as period increases due to greater shielding, which means that Ge must be larger than C. This eliminates choices Ge < P < Al < C and Ge < Al < P < C. Now, we must evaluate Al vs. P. These two atoms are in the same period. However, atomic radius decreases as you go left to right in the same period due to a greater effective nuclear charge, which means that P is smaller than Al. Thus, the atoms from smallest to largest atomic radius is C < P < Al < Ge

What is the reactivity, as indicated by the tendency to lose an electron, of sodium compared to potassium? A. This cannot be determined from the information given. B. Potassium has a lower reactivity because potassium has more protons than sodium. C. Potassium has a higher reactivity because the valence electron on potassium is farther from the nucleus. D. Both metals have the same reactivity because the potassium and sodium valence electrons experience the same effective nuclear charge.

Answer C Reactivity of metallic elements increases down a column of the periodic table. This increase in reactivity corresponds with increased shielding from inner electron shells, increased atomic radius, and decreased ionization energy. Thus, electrons are easier to remove in potassium versus sodium.

Which of the following gives the ground-state electron configuration of a calcium atom once it acquires an electric charge of +2? A. [Ar] 4s23d2 B. [Ar] 4s2 C. [Ar] D. [Ar] 4s24p2

Answer C The ground-state electron configuration of a calcium atom once it acquires an electric charge of +2 is [Ar]. A calcium atom normally contains 20 electrons, so if it acquires a charge of +2, it must have lost 2 electrons, leaving just 18. Only [Ar] accounts for 18 electrons.

Compared to the atomic radius of S, the atomic radius of Al is: A. smaller, due to decreased nuclear charge. B. smaller, due to increased nuclear charge. C. larger, due to increased nuclear charge. D. larger, due to decreased nuclear charge.

Answer D Moving left to right across a period, nuclear charge increases due to increasing atomic number (number of protons). As the positive nuclear charge increases, effective nuclear charge increases and electrons are pulled closer to the nucleus, resulting in a decreased atomic radius. Aluminum is therefore larger than sulfur. This problem can also be treated as a two-by-two if you know the periodic trend for atomic radius, which decreases up and to the right. Based on this trend, it can be determined that Al is larger than S, eliminating the choices using "smaller." The distinction between the final two choices can then be determined based on the effect of nuclear charge.

Which of the following is true of ionization energy? A. It increases with period, and the second ionization energy is greater than the first. B. It decreases with period, and the first ionization energy is greater than the second. C. It increases with period, and the first ionization energy is greater than the second. D. It decreases with period, and the second ionization energy is greater than the first.

Answer D his is a 2 x 2 question that is best approached by evaluating one of the arguments to eliminate answer choices. As period increases, ionization energy decreases due in part to the greater degree of shielding present. Thus, we can eliminate the two choices that begin with the choice "it increases." Evaluating the other argument, the second ionization energy is always greater than the first because electrons are more tightly bound after one is displaced (a more positively charged atom is less likely to give up an additional electron). Thus, ionization energy decreases with period and the second ionization energy is greater than the first.

In organic solution, F- deprotonates dissolved HCl. Which of the following explains this observation? A. F- has a smaller radius than Cl-. B. F- is a stronger acid than Cl-. C. F- has a greater electronegativity than Cl-. D. F- has a lower ionization energy than Cl-.

Answer: A Since F- has a smaller radius than does Cl-, it is less stable with excess charge, and therefore a better Bronsted base. It outcompetes Cl- for the proton.

What are the 7 common strong acids?

HCl - Hydrochloric HNO3 - Nitric acid H2SO4 - Sulfuric acid HBr - hydronromic HI hydroiodic HClO4 Perchloric HClO3 Chloric