There are 2 atoms in NaCl. This is because there is 1 atom of Na (sodium) and 1 atom of Cl (chlorine) in each NaCl molecule. Elements by themselves do not have a "number of atoms"- if you're talking about the atomic number, it's the number of protons (or electrons in a neutral atom) of an element.
The Gulf Stream affects the climate in Britain by bringing warm water from the Caribbean to North West Europe. This keeps the climate in Britain warmer than other places at a similar latitude.
