In case of SF4 there are 6 electrons in the outermost shell of Sulphur, out of these 6 electrons, 4 are utilized in bonding with fluorine and thus two unshared electrons are there. Which leads to the lone pair as shown below. Contribute to make this site more informative.
For calculation of number of atoms we have to calculate the number of moles present in 1gram carbon. Multiply the number of moles with Avogadro number. Step I Number of moles in 1 gram of carbon = given mass / molar mass Molar mass (molecular or atomic mass expressed in grams) = 12g So the