C is the answer because that is an actual chemical change where the sulfur and iron are not separate from each other anymore
Answer: [Ne] 3s¹ sodium electron configuration
For radioactive decay, we can relate current amount, initial amount, decay constant and time using:
N = No x exp(-λt)
Half-life = ln(2)/λ
λ = ln(2) / 5730
N/No = 80% = 0.8
0.8 = exp( -ln(2)/5730 x t)
t = 1844 years
3, 1, 5, 4, 3, spontaneous
