They represent elements by using symbols
<span>density = mass / volume
given the quotient , we have density and mass, volume can be easily calculated as:
volume = mass / p =15.5 g / 0.789 g/cm^3
=~ 20 cm^3 (dimension ally constant)</span>
SiO2 is the only possible choice because the other formulas contain metals. how do we know this? because the other formulas contain elements located on the left of the “staircase” on the periodic table that separates metals from non-metals.
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Zeff = Z - S
Here, Z is the number of protons in the nucleus, that is, atomic number, and S is the number of nonvalence electrons.
For boron, the electronic configuration is 1s₂ 2s₂ 2p₄
Z = 5, S = 2
Zeff = 5-2 = +3
For O, electronic configuration is 1s₂ 2s₂ 2p₄
Z = 8, S = 2
Zeff = 8-2 = +6
Hence, the correct answer is second option, that is, +3 and +6, the Zeff of boron is smaller in comparison to O, thus, boron exhibits a bigger size than O.
