It depends on the strength of the H-A bond. The weaker the bond, the lesser the energy required to break it. Hence, the acid is strong.
The polarity of the H-A bond affects its acid strength. If the bond is highly polar, the proton tends to leave the molecule more easily, making it a strong acid.
However, bond strength is more important when we consider and compare acid strengths of elements in the same group of the periodic table, using the above two factors.
Nevertheless, when we compare the acid strengths of elements in the same row, priority is given to the polarity of the H-A bond.
The atomic size of A also affects the acid strength. As the atom becomes larger, the bond gets weaker. Consequently, acid strength increases.