91影视

For each element, we need to first find its location on the periodic table and then find the noble gas in the previous row. a. Nickel (Ni, \(Z=28\)) is in period 4 of the transition metals. The noble gas that precedes it is Argon (Ar, \(Z=18\)). b. Niobium (Nb, \(Z=41\)) is in period 5 of the transition metals. The noble gas that precedes it is Krypton (Kr, \(Z=36\)). c. Hafnium (Hf, \(Z=72\)) is in period 6 of the transition metals. The noble gas that precedes it is Xenon (Xe, \(Z=54\)). d. Astatine (At, \(Z=85\)) is in period 6 of the halogens. The noble gas that precedes it is Xenon (Xe, \(Z=54\)).

Now, we write the shortcut electron configuration for each element, starting with the symbol of the preceding noble gas in brackets, followed by the electron configuration of the remaining electrons. a. Nickel (Ni, \(Z=28\)): The preceding noble gas is Argon (Ar, \(Z=18\)), so our starting point is [Ar]. Since nickel has 10 more electrons than argon, we add 4s虏, 3d鈦�. \[ \text{Ni: [Ar] 4s^2 3d^8} \] b. Niobium (Nb, \(Z=41\)): The preceding noble gas is Krypton (Kr, \(Z=36\)), so our starting point is [Kr]. Since niobium has 5 more electrons than krypton, we add 5s虏, 4d鲁. \[ \text{Nb: [Kr] 5s^2 4d^3} \] c. Hafnium (Hf, \(Z=72\)): The preceding noble gas is Xenon (Xe, \(Z=54\)), so our starting point is [Xe]. Since hafnium has 18 more electrons than xenon, we add 6s虏, 4f鹿鈦�, 5d虏. \[ \text{Hf: [Xe] 6s^2 4f^{14} 5d^2} \] d. Astatine (At, \(Z=85\)): The preceding noble gas is Xenon (Xe, \(Z=54\)), so our starting point is [Xe]. Since astatine has 31 more electrons than xenon, we add 6s虏, 4f鹿鈦�, 5d鹿鈦�, 6p鈦�. \[ \text{At: [Xe] 6s^2 4f^{14} 5d^{10} 6p^5} \]