Answer: The energy of the 4-s subshell is lower than the energy of 3-d subshell.
Explanation:
During the filling of electrons in subshells, the lower energy levels are filled before the higher energy levels. Also known as Aufbau principle.
Energy of the sublevel = (n + l) 
where : n = Principal quantum number 
              l = Azimuthal quantum number(s=0,p=1,d=2,f=3)
Energy of 4-s subshell= (4+0) = 4
Energy of 3-d subshell=(3+2) = 5
Energy of 4-s subshell is lower than the energy of 3-d subshell, that is why 4s orbital is filled before the 3-d subshell.
 
        
                    
             
        
        
        
Answer:
84.2 grams
Explanation:
you have to multiply 8.42x10^18 to get the answer above
 
        
             
        
        
        
Answer:
<h2>Density = 0.00026 g/mL</h2>
Explanation:
The density of a substance can be found by using the formula
<h3>

</h3>
From the question
mass of air = 1.2 g
volume = 4,555 mL
Substitute the values into the above formula and solve for the density
That's
<h3>

</h3>
= 0.0002634
We have the final answer as
<h3>Density = 0.00026 g/mL</h3>
Hope this helps you
 
        
             
        
        
        
<u>Answer:</u>
Exothermic Reaction are those reaction, in which energy is released while in endothermic reaction are those, in which energy is absorbed.
<u>Explanation:</u>
First Reaction:
As in this reaction, energy is released 
½H2(g) + ½I2(g) → HI(g), ΔH = +6.2 kcal/mole 
so it is <em>exothermic reaction</em>
Second reaction:
As in this reaction, energy is absorbed
21.0 kcal/mole + C(s) + 2S(s) → CS2(l)
so it is <em>endothermic reactions</em>.