The Density Calculator uses the formula p=m/V, or density (p) is equal to mass (m) divided by volume (V). The calculator can use any two of the values to calculate the third. Density is defined as mass per unit volume.
Answer:
9
Explanation:
mass number = protons + neutrons
= 4 + 5 = 9
Answer :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and the unpaired electrons present in the molecule.
The given molecule is, 
Beryllium has '2' valence electrons and fluorine has '7' valence electrons. Beryllium is the central atom and fluorine is the terminal atom.
Total number valence electrons in
= 2 + 2(7) = 16
According to the Lewis-dot structure, there are '4' number of bonding electrons and 12 number of non-bonding electrons (lone-pair).
The Lewis-dot structure is shown below.