Answer:
The correct answer is - sulfur.
Explanation:
In the periodic table, there are 18 groups and 7 rows or periods arranged according to their atomic number or electronic configuration. In the question, it is mentioned that the desired element atomic mass is less than the atomic mass of the selenium which is 78.96, and more than oxygen which is 15.99 with 6 electron valence and present in the third row.
As it has 6 valency of electron it must be in the 16 group of the table that comprises the 6 valency and as it is located in the 3rd row it must be sulfur that also has an atomic mass between selenium and oxygen.
Answer : The mass of solute in solution is 
.
Solution : Given,
Molarity = 0.730 M
Volume of solution = 1.421 L
Molar mass of sodium carbonate = 105.98 g/mole
Formula used for Molarity :
where,
w = mass of solute
M = Molar mass of solute
V = volume of solution in liter
Sodium carbonate is solute and water is solvent.
Now put the given values in above formula, we get the mass of solute in solution.
By rearranging the terms, we get
Therefore, the mass of solute in solution is .
Concrete is formed of sand. Is it incorrect to suggest that some houses are built using concrete blocks?
Answer:
I have no clue this qestion is kinda stumping but it a really good question it got me thinking but i don't know if there is a right answer
Explanation:
I don't know
Answer:
1) Ca: [Ar]4s²
2) Pm: [Xe]6s²4f⁵
Explanation:
1) Ca:
Its atomic number is 20. So it has 20 protons and 20 electrons.
Since it is in the row (period) 4 the noble gas before it is Ar, and the electron configuration is that of Argon whose atomic number is 18.
So, you have two more electrons (20 - 18 = 2) to distribute.
Those two electrons go the the orbital 4s.
Finally, the electron configuration is [Ar] 4s².
2) Pm
The atomic number of Pm is 61, so it has 61 protons and 61 electrons.
Pm is in the row (period) 6. So, the noble gas before Pm is Xe.
The atomic number of Xe is 54.
Therefore, you have to distribute 61 - 54 = 7 electrons on the orbitals 6s and 4f.
The resultant distribution for Pm is: [Xe]6s² 4f⁵.
