Radioactive material obeys 1st order decay kinetics,
For 1st order reaction, we have
k =

where, k = rate constant of reaction
Given: Initial conc. 100, Final conc. = 6.25, t = 18.9 hours
∴ k =

= 0.1467 hours^(-1)
Now, for 1st order reactions: half life =

= 4.723 hours.
Chlorine, Cl , is located in period 3, group 17 of the periodic table, and has an atomic number equal to 17 . This tells you that a neutral chlorine atom will have a total of 17 electrons surrounding its nucleus. Now, notice that the first energy level doesn't not contain a p-subshell,
A difference between plant cells and animal cells is that most animal cells are found whereas most plant cells are rectangular. Plant cells have rigid cell wall that surrounds the cell membrane.animals do not have a cell wall