Calculate the number of atoms in 80.0g of calcium. [Relative atomic mass of Ca = 40]

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '