How many orbitals in iron are half-filled, that is, have only one electron? (A) 1
(B) 2
(C) 3
(D) 4

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8

c. 4.54 x 10–12 j happens to be correct