Answer
(b), (d), (e) are true, while (a) and (c) are false.
Work Step by Step
a) Statement is false because Magnesium has symbol $Mg$, not $Mn$
($Mn$ is a symbol of manganese)
b) True. As all elements Phosphorus (P) , Arsenic (As) and Bismuth (Bi) are a part of group (family) 15.
c) False. Gallium (Ga) $loses$ three electrons to form its $cation$, while Selenium (Se) and Bromine(Br) gain electrons to form anions.
d) True. All elements that lie from group 3 -12 are called transition elements. Cobalt (Co), Nickel (Ni) and Mercury (Hg) are transition metals
e) True . Correct name for $TiO_{2}$ $is$ Titanium dioxide
