Answer
See explanation
Work Step by Step
a. An alkali metal in period 6
Alkali metals = Group 1 elements: Li, Na, K, Rb, Cs, Fr
Period 6 = the sixth row → Cesium (Cs)
Answer: Cesium (Cs)
b. A transition metal in period 5, group 8
Period 5 = fifth row
Group 8 = Fe’s column (Group 8 metals)
In period 5, group 8 element is Ruthenium (Ru)
Answer: Ruthenium (Ru)
c. A main group element in period 3, group 7A
Group 7A (17) = halogens: F, Cl, Br, I, At
Period 3 = third row → Chlorine (Cl)
Answer: Chlorine (Cl)
d. A main group element in period 2, group 2A
Group 2A (2) = alkaline earth metals: Be, Mg, Ca, Sr, Ba, Ra
Period 2 = second row → Beryllium (Be)
Answer: Beryllium (Be)
e. A halogen in period 2
Halogens = Group 17 → F, Cl, Br, I, At
Period 2 → Fluorine (F)
Answer: Fluorine (F)
f. An inner transition metal with one 4f electron
Inner transition metals = lanthanides and actinides
4f¹ means it’s the first element in the lanthanide series → Cerium (Ce) has 4f¹5d¹6s² configuration, but Lanthanum (La) has 4f⁰.
So the first with one 4f electron is Cerium (Ce)
Answer: Cerium (Ce)
