A monoatomic anion (A^-) has 45 neutrons and 36 electrons. Atomic...

Number of electrons in $A^{-}$ is $36$.

Number of electrons in neutral atom $A = 36 - 1 = 35$.

Atomic number of $A = 35$.

Number of protons in $A = 35$.

Atomic mass of $A = \text{Number of protons} + \text{Number of neutrons} = 35 + 45 = 80$.

The element with atomic number $35$ is Bromine ($\text{Br}$).

Bromine belongs to Group $17$ of the periodic table.

The physical state of Bromine at room temperature is liquid.

Answer: $80, 17$, liquid