## Chemistry 9th Edition

a. $^{58}_{27}Co$ b. $^{10}_5B$ c. $^{23}_{12}Mg$ d. $^{132}_{53}I$ e. $^{47}_{20}Ca$ f. $^{65}_{29}Cu$
We refer to the periodic table when determining the element. Note that the formula $^A_ZX$ represents an atom with a mass number of A and an atomic number of Z. Therefore, we may write the following: a. Atomic mass = number of protons + number of neutrons = 27+31=58. The element with 27 protons is Cobalt (CO). Therefore the formula is $^{58}_{27}Co$. b. Boron has an atomic number of 5. Therefore the formula is $^{10}_5B$. c. Magnesium (Mg) has 12 protons. $^{23}_{12}Mg$ d. The element with an atomic number of 53 is Iodine (I). Atomic mass = number of protons + number of neutrons = 53+79 = 132. $^{132}_{53}I$ e. The element with an atomic number of 20 is Calcium (Ca). Atomic mass = number of protons + number of neutrons = 20+27=47. $^{47}_{20}Ca$ f. The element with 29 protons is Copper (Cu). $^{65}_{29}Cu$