Answer
a. transition element;
b. main group element;
c. transition element;
d. main group element
Work Step by Step
a. Cr is a transition metal since it's part of the transition metal elements on the periodic table.
b. Br is in the 7A group which means that it is a main group element.
c. Mo is a transition metal since it's part of the transition metal elements on the periodic table.
d. Cs is in the 1A group which means that it is a main group element.
