Question

isotope symbol, element name, short name, atomic number, mass number, # of protons, # of neutrons, # of electrons
cd - 110, cadmium - 110, cd - 110, 48, 110, 48, 110 - 48 = 62, 48
c - 12, carbon - 12, c - 12
sc - 45, sc - 45
y - 89, 39, 89
tb - 158, 158, 65

Explanation:

Step1: Recall atomic number rules

Atomic number = number of protons = number of electrons in a neutral atom. Mass number = number of protons + number of neutrons.

Step2: Fill in carbon - 12 row

Atomic number of carbon is 6. So number of protons = 6, number of electrons = 6. Mass number is 12, number of neutrons = 12 - 6 = 6. Isotope symbol is $^{12}_{6}C$.

Step3: Fill in scandium - 45 row

Atomic number of scandium is 21. So number of protons = 21, number of electrons = 21. Mass number is 45, number of neutrons = 45 - 21 = 24. Isotope symbol is $^{45}_{21}Sc$.

Step4: Fill in yttrium - 89 row

Number of protons = 39 (given atomic number), number of electrons = 39. Number of neutrons = 89 - 39 = 50. Isotope symbol is $^{89}_{39}Y$.

Step5: Fill in terbium - 158 row

Atomic number = number of protons = 65. Number of electrons = 65. Number of neutrons = 158 - 65 = 93. Isotope symbol is $^{158}_{65}Tb$.

Answer:

Isotope Symbol	Element Name	Short Name	Atomic Number	Mass Number	# of Protons	# of Neutrons	# of Electrons
$^{45}_{21}Sc$	Scandium - 45	Sc - 45	21	45	21	24	21
$^{89}_{39}Y$	Yttrium - 89	Y - 89	39	89	39	50	39
$^{158}_{65}Tb$	Terbium - 158	Tb - 158	65	158	65	93	65