So they can tell what exact species it is.
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.
Format Method - Writing the symbol of the cation and then the anion. Add whatever subscripts in order to balance the charges.
Crisscross Method - The numerical value of the charge of each ion is crossed over and becomes the subscripts for the other ion.
The answer is 9.03 × 10²⁴<span> molecules.
</span><span>Avogadro's number is the number of units (atoms, molecules) in 1 mole of substance.
Make the proportion.
</span><span>6.02 × 10²³ molecules per 1 mol
</span>x per 15 mol
6.02 × 10²³ molecules : 1 mol = x : 15 mol
x = 6.02 × 10²³ molecules * 15 mol * 1 mol
x = 90.3 × 10²³ molecules
x = 9.03 × 10 × 10²³ molecules
x = 9.03 × 10²³⁺¹ molecules
x = 9.03 × 10²⁴ molecules
