Answer:
Potassium
1s2 2s2 2p6 3s2 3p6 4s1
Explanation:
The atom having only one electron its outermost shell must belong to an element in group one of the periodic table.
Having noted that, we proceed to find out what element in group one that has the atom just described in the question.
That atom must belong to an element in the fourth period. The only group 1 element in the fourth period is potassium.
The electron configuration of potassium is;
1s2 2s2 2p6 3s2 3p6 4s1
<u>Answer:</u> The wavelength of spectral line is 656 nm
<u>Explanation:</u>
To calculate the wavelength of light, we use Rydberg's Equation:

Where,
= Wavelength of radiation
= Rydberg's Constant = 
= Final energy level = 2
= Initial energy level = 3
Putting the values in above equation, we get:

Converting this into nanometers, we use the conversion factor:

So, 
Hence, the wavelength of spectral line is 656 nm
Answer:
B. It represents the change in enthalpy for the reaction.
Explanation:
The potential energy diagram for a chemical reaction shows its potential energy plotted against the reaction progress coordinate. The potential energy diagram shows how the potential energy of reactants and products vary as reactants are converted into products.
The potential energy of the system refers to energy stored in the chemical bonds of reactants and products. The difference between the potential energy of reactants and products is known as the enthalpy of reaction. This difference in potential energy may be positive or negative. A positive difference in potential energy implies an endothermic reaction while a negative difference in potential energy implies an exothermic reaction.
Answer:

Explanation:
Hello there!
In this case, according to the given information it will be firstly necessary to set up the chemical equation taking place:

We infer we need to calculate the moles of NH3 by using both of the moles of N2 and H2 at the beginning, in order to identify the limiting reactant:

Thus, since hydrogen yields the fewest moles of ammonia, we conclude that we are just able to yield 4 moles of NH3.
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