Answer: cause oxegeon is harmful then helium
Explanation:
Aufbau principle:
Electrons are added one at a time from the lowest energy orbitals available until all the orbitals are filled.
According to the Aufbau principle, electrons fill lower energy orbitals first.
(i) Boron (Z = 5)
Electronic configuration =
(ii) Neon (Z = 10)
Electronic configuration =
(iii) Aluminium (Z = 13)
Electronic configuration =
(iv) Chlorine (Z = 17)
Electronic configuration =
(v) Calcium (Z = 20)
Electronic configuration =
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Models of atoms and compounds help in understanding of concepts of reactions in chemistry.
<h3>What are models?</h3>
Models are objects used to provide a visual representation of certain things or structures.
Models are widely employed in chemistry because of their usefulness in strengthening understanding of concepts.
The importance of models in chemistry include:
- they help students to be able to visualize the structures of atoms and compounds in a macroscopic scale
- they provide an a clearer understand of how atoms combine to form products in reactions.
Therefore, models help in understanding of concepts of reactions in chemistry.
Learn more about chemistry models at: brainly.com/question/4769748
Answer 1) : The density of the hot air inside the balloon can be found out by using ideal gas equation;
PV = nRT;
As n is number of moles and in gases, number of moles along with mass per mole is equal to the density of the gas.
If the moles in the gas are more the density will be more.
here, density (ρ) = mass (m) / volume (V); substituting in the ideal gas equation we get,
ρ = mP / RT
Answer 2) ρ (hot air) = ρ (cold air) X 
Here according to the formula because T(hot air) >T(cold air),
So, the density of hot air greater than the density of cold air.
The relationship between the ρ (h) = ρ(c) X
