Graphic illustration of basicity of EHn
| Periodic table | Group 15 | Group 16 | Group 17 |
| Formula Electron Density Map (calculated) | NH3 | H2O  | HF |
| basicity | weak base | v weak base | not basic |
  decreasing basicity (less red at E)Stronger bases have higher electron density (more red) at the atom accepting the proton. | HCl  not basic | ||
HBr  not basic | |||
HI  not basic | |||