The number of lone pairs of electrons on the central I atom in I$$_3^ - $$ is ____________.

250 mL of 0.5 M NaOH was added to 500 mL of 1 M HCl. The number of unreacted HCl molecules in the solution after complete reaction is ___________ $$\times$$ 10²¹. (Nearest integer)

(N_A = 6.022 $$\times$$ 10²³)

The Azimuthal quantum number for the valence electrons of Ga⁺ ion is ___________.

(Atomic number of Ga = 31)

The spin-only magnetic moment value for the complex [Co(CN)₆]^4$$-$$ is __________ BM.

[At. no. of Co = 27]