SN refers to the chemical element tin (Sn) in the periodic table. Tin has an atomic number of 50, which means it has 50 protons and 50 electrons in its neutral state.
To determine the number of valence electrons, we look at the electron configuration of tin. The electron configuration of tin is [Kr] 5s^2 4d^10 5p^2.
The outermost shell of tin is the 5th energy level (n=5), which consists of the 5s and 5p orbitals. To find the number of valence electrons, we count the electrons in the outermost shell. In this case, there are 2 electrons in the 5s orbital and 2 electrons in the 5p orbital.
Therefore, tin (Sn) has 4 valence electrons.