Answer:
Which scientist developed the first model of the atom that showed the structure of the inside of an atom
Ernest Rutherford
We have to convert 2100 kilojoule into calories.
2100 Kilojoule is equal to 500 Calories.
The chemical reaction gives off 2100 Kilojoule of heat energy which indicates that the reaction is exothermic in nature. Calorie and Kilojoule both are units of energy. We know, 1 calorie=4.2 kilojoule= 4.2 KJ. So 4.2 KJ is equal to 1 Calorie i.e, 4.2 KJ= 1 Calorie. So, to convert KJ to calorie, we have to divide the energy given in KJ by quantity 4.2. Hence, 2100 Kilojoule energy is equal to 
Calorie= 500 Calories.
<span>
</span>The solution would be like this for this
specific problem:
<span> (atomic number) - (core electrons)</span>
Boron:
Atomic number: 5
Core electrons: 2
Boron will have the
following: 2 core electrons and 3 valence electrons.
(atomic number) - (core electrons)------> (5) - (2) = +3
<span>
</span><span>Oxygen: </span><span>
<span>Atomic number: 8 </span>
<span>Core electrons: 2 </span></span>
<span>Boron will have the
following: 2 core electrons and 6 valence electrons. </span><span>
<span>(atomic number) - (core electrons)------> (8) - (2) = +6 |
So the answer would be +3 and +6</span>.</span><span>
I hope this helps and if you have any further questions, please don’t hesitate
to ask again. </span>
