Answer:
it is the formulae of glucose
It is a compound made of carbon,oxygen,hydrogen
From the periodic table, beryllium has an atomic number 4. This means that beryllium has 4 electrons.
Now, the first energy level can hold only 2 electrons (which will occupy the s sublevel) wile the remaining two electrons will occupy the second energy level (also in the s sublevel).
Based on the above, the electronic configuration of beryllium will be as follows:
1s2 2s2
I think the correct answer from the choices listed above is option A. The key characteristic by which Dmitri Mendeleev arranged his periodic table was that the elements are arranged in increasing atomic number. Hope this answers the question.
1. D. 5
2. B. 2
3. A. fluroine
Hope this helps you!!
Have a wonderful day!
