Solutions to Practice Problems Week 3

1. Classify as a metal, nonmetal or metalloid: Cs, Os, Ge, He, I, Al
 Cs Metal Os Metal Ge Metalloid He Nonmetal I Nonmetal Al Metal

1. Determine the number of protons, electrons and neutrons for the following:
 Isotope→ 18O 35Cl 78Se 26Al3+ 79Br- Protons 8 17 34 13 35 Electrons 8 17 34 10 36 Neutrons 10 18 44 13 44

1. Show both nlx and “boxes and arrows” electron configurations for each of the following: P, Fe, Tc

Note: There are discernible spaces between the boxes for s, p and d orbitals. These spaces are necessary to distinguish the identity of the electrons (the arrows). Without the spaces, the display cannot be interpreted.

1. For each of the following, give (a) the electron configuration using nlx notation, (b) the number of unpaired electrons and (c) the orbital from which the first electron would be lost: sulfur, zinc, niobium (Nb) and tellurium (Te)
 Atom Electronic Configuration # unpaired electrons Orbital Most Easily Ionized Sulfur Z = 16 2 3p Zinc Z = 30 0 3d Niobium Z = 41 3 4d Tellurium Z = 52 2 5p

1. Give the family name (or group #) and the number of valence electrons in an atom of each of the following: Cs, Ge, At, Xe

• Cs: alkali metals (IA), one valence electron
• Ge: carbon group (IVA), four valence electrons
• At: the halogens (VIIA), seven valence electrons
• Xe: the rare gases (VIIIA), either zero or eight valence electrons

1. Circle the incorrect configurations below and then correct them.

 Given Correct F: 1s22s22p5 OK Mn: [Ar]4s24d5 Mn: [Ar]4s23d5 Rb: [Kr]5s1 OK N: 1s22s22p N: 1s22s22p3