Answer:
A- beryllium
B- calcium
C- magnesium
Explanation
NOTE: all element in group 2 have 2 balance electrons
First let’s start with B- number of electrons= number of protons which is equal to the atomic number. therefore, the answer is calcium as it’s atomic number is 20
C- magnesium will have three energy levels considering it has 12 electrons (2,8,2).
A- beryllium is the lightest one in group 2 as it has the atomic mass of 9.0122.
Yes, the crystals will have more time to form and therefore are more likely to be larger compared to one that is cooled quickly.
Answer:

Explanation:
First thing is we have assume all the percents are grams so we have
68.279g C, 6.2760g H, 3.7898g N, and 21.656g O
Now convert each gram to moles by dividing the the molar mass of each element
68.279g/12.01g= 5.685 moles of C
6.2760g/1.01g= 6.214 moles of H
3.7898g N/14.01g= 0.271 moles of N
21.656g O/ 16.00g= 1.354 moles of O
Now to find the lowest ratios divide all the moles by the smallest number of moles you found, in our case, the smallest moles is 0.271 moles of N so divide everything by that....
5.685 moles/0.271 moles ------> ~21 C
6.214 moles/0.271 moles --------> ~23 H
0.271 moles / 0.271 moles ---------> 1 N
1.354 moles/ 0.271 moles ----------> ~5 O
So the empirical formula is C21H23NO5 
The correct option is (e) 0.389 moles.
The number of moles represented by 21.7 g fe 0.389 moles.
Solution:
(21.7g) x (1mol/55.85g) = 0.389 moles
<h3>What is moles?</h3>
The mole, represented by the symbol mol, is the fundamental SI unit of material quantity. The amount of a substance determines how many elementary entities of that substance are present in an object or sample. Since the SI fundamental units were revised in 2019, the mole is now exactly defined as 6.022140761023.
<h3>Why the mole is a base unit?</h3>
The amount of a substance determines how many elementary entities of that substance are present in an object or sample. Since the SI fundamental units were revised in 2019, the mole is now exactly defined as 6.022140761023.
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