substitute: <span><span>t<span>1/2</span></span>=<span><span>ln(2)</span>k</span>→k=<span><span>ln(2)</span><span>t<span>1/2</span></span></span></span>
Into the appropriate equation: <span>[A<span>]t</span>=[A<span>]0</span>∗<span>e<span>−kt</span></span></span>
<span>[A<span>]t</span>=[A<span>]0</span>∗<span>e<span>−<span><span>ln(2)</span><span>t<span>1/2</span></span></span>t</span></span></span>
<span>[A<span>]t</span>=(250.0 g)∗<span>e<span>−<span><span>ln(2)</span><span>3.823 days</span></span>(7.22 days)</span></span>=67.52 g</span>
Answer: The empirical formula is 
Explanation:
If percentage are given then we are taking total mass is 100 grams.
So, the mass of each element is equal to the percentage given.
Mass of Br= 58.37 g
Mass of F = (100-58.37) = 41.63 g
Step 1 : convert given masses into moles.
Moles of Br=
Moles of F =
Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.
For Br = 
For F = 
The ratio of Br: F= 1 : 3
Hence the empirical formula is
Answer: 57 neutrons
Explanation: Ruthenium has an atomic number of 44, meaning it has 44 electrons, 44 protons, and 57 neutrons.
Strontium has an electron configuration of [Kr]5s²
<h3>Further explanation </h3>
In an atom there are levels of energy in the shell and sub shell
This energy level is expressed in the form of electron configurations.
Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d and f. The maximum number of electrons for each sub shell is
s: 2 electrons
p: 6 electrons
d: 10 electrons and
f: 14 electrons
From an electron configuration of [Kr]5s² can be concluded :
- element is in period 5 (5 = shell)
- element is group 2(valence electron =2 and block s)
- has atomic number 38 (Kr = 36 + 2(valence elektron from 5s²)
If we look at the periodic system, the elements that meet the requirements in question are Strontium (Sr)
