The negative (oxygen) end of water is attracted to the positive sodium ion in the salt, extracts it from the lattice and more water molecules surround it (i.e. dissolve it). The same is true for the positive (hydrogen) end of water and the negative chloride ion in the salt.
According to nitrogen's electron configuration table, an atom of nitrogen contains two electrons in its first energy level (both in the s sub-shell) and five electrons in its second energy level (two in the s sub-shell and three in the p sub-shell). A more accurate Bohr model of a nitrogen atom could look like this: In the refined Bohr model, a nitrogen atom has a central nucleus, composed of seven protons and seven neutrons, surrounded by seven electrons.
In chemistry and atomic physics, an electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the 1 shell, followed by the 2 shell, then the 3 shell, and so on farther and farther from the nucleus. The shells correspond with the principal quantum numbers or are labeled alphabetically with letters used in the X-ray notation. Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.