Answer:
The nuclear charge increases from boron to carbon, but there is no additional shielding( that is no additional shells).
Explanation:
First of all, we must know the electron configuration of carbon and boron.
Boron- 1s2 2s2 2p1
Carbon- 1s2 2s2 2p2
Moving from boron to carbon, the effective nuclear charge increases without a corresponding increase in the number of shells. Remember that shielding increases with increase in the number of intervening shells between the outermost electron and the nucleus. Since there isn't an increase in shells, boron experience a lower screening effect.
From
Zeff= Z- S
The Z for carbon is 6 while for boron is 5 even though both have the same number of screening electron S(4 screening electrons). Hence it is expected the Zeff(effective nuclear charge) for boron will be less than that of carbon.
It’s A dalton he is the one who figured out matter
Answer:

Explanation:
Half time is period required to desintegrating the half of the initial number of atoms. Then, the total time is:


Complete Question
The complete question is shown on the first uploaded image
Answer:
The concentration of
that should used originally is 
Explanation:
From the question we are told that
The necessary elementary step is

The time taken for sixth of 0.5 M of reactant to react 
The time available is 
The desired concentration to remain
Let Z be the reactant , Y be the first product and X the second product
Generally the elementary rate law is mathematically as

Where k is the rate constant ,
is the concentration of Z
From the elementary rate law we see that the reaction is second order (This because the concentration of the reactant is raised to power 2 )
For second order reaction

Where
is the initial concentration of Z which a value of 
From the question we are told that it take 9 hours for the concentration of the reactant to become


So


=> 
For 




