Chapter 2 - Atoms, Molecules, and Ions - Questions and Exercises - Exercises - Page 85: 2.57

(a) representative (b) transition metal (c) representative (d) inner transition metal

(a) Silicon, or Si, is a representative element because it is a main-group element, meaning it is in the "A" group elements. Silicon is in group 4A of the periodic table. (b) Cr, or chromium, is a transition metal because it is in the middle section of the periodic table called the "B" section. (c) Magnesium, or Mg, is a representative element because it is a main-group element, meaning it is in the "A" group elements. Magnesium is in group 2A of the periodic table. (d) Np, or neptunium, is an inner transition metal because it is located in the actinide series, the row of metals following actinium. Any element located in the row following lanthanum or actinium is considered an inner transition metal.