Problem 75 - Chemistry Central Science

Question

(a) If we arrange the elements of the second period (Li-Ne) in order of increasing first ionization energy, where would hydrogen fit into this series? (b) If we now arrange the elements of the third period (Na-Ar) in order of increasing first ionization energy, where would lithium fit into this series? (c) Are these series consistent with the assignment of hydrogen as a nonmetal and lithium as a metal?

Step-by-Step Solution

Answer

When arranged in order of increasing first ionization energy, hydrogen fits between carbon and oxygen in the second period, and lithium fits between sodium and aluminum in the third period. This is consistent with the assignment of hydrogen as a nonmetal and lithium as a metal.

Step 1: Arrange the elements of second and third periods.

The elements of the second period are Li, Be, B, C, N, O, F, Ne. The elements of the third period are Na, K, Al, Si, P, S, Cl, Ar.

Step 2: Find ionization energies

First ionization energies (in eV) of the elements are: First period: H (13.6) Second period: Li (5.4), Be (9.3), B (8.3), C (11.3), N (14.5), O (13.6), F (17.4), Ne (21.6) Third period: Na (5.1), Mg (7.6), Al (5.99), Si (8.2), P (10.5), S (10.4), Cl (12.97), Ar (15.76)

Step 3: Arrange elements by increasing ionization energy

Second period (excluding H): Li (5.4), Be (9.3), B (8.3), C (11.3), N (14.5), O (13.6), F (17.4), Ne (21.6) Third period (excluding Li): Na (5.1), Mg (7.6), Al (5.99), Si (8.2), P (10.5), S (10.4), Cl (12.97), Ar (15.76)

Step 4: (a) Find the position where hydrogen fits into the second period

Compare the first ionization energy of hydrogen (H: 13.6 eV) to the second period elements: Li (5.4) < B (8.3) < Be (9.3) < C (11.3) < H (13.6) < O (13.6) < N (14.5) < F (17.4) < Ne (21.6) The position of hydrogen in the second period is between carbon and oxygen.

Step 5: (b) Find the position where lithium fits into the third period

Compare the first ionization energy of lithium (Li: 5.4 eV) to the third period elements: Li (5.4) < Na (5.1) < Al (5.99) < Mg (7.6) < Si (8.2) < S (10.4) < P (10.5) < Cl (12.97) < Ar (15.76) The position of lithium in the third period is between sodium and aluminum.

Step 6: Determine if the series are consistent with the assignment of hydrogen as a nonmetal and lithium as a metal

In the second period, hydrogen is placed between carbon and oxygen, which are both nonmetals. Therefore, it is consistent with hydrogen being a nonmetal. In the third period, lithium is placed between sodium and aluminum, which are both metals. Therefore, it is consistent with lithium being a metal. Thus, the series are consistent with the assignment of hydrogen as a nonmetal and lithium as a metal.