Six strong acids (HCL, HBr, HI, HNO3, H2SO4, HCLO4) fully ionise to form the highly stable anions CL-, BR-, I-, NO3-, SO4-2, CLO4-
For the remaining weak acids (HA) their relative acidity can be determined by comparing the relative electron densities of their conjugate bases (A-). The lower the electron density, the more stable the conjugate base.