Answer:
(a) B3+ : 1s2
(b) O- : 1s2 2s2 2p5
(c) Cl3+ : 1s2 2s2 2p6 3s2 3p2
(d) Ca2+ : 1s2 2s2 2p6 3s2 3p6
(e) There is no element with symbol [T]
Step-by-step explanation:
(a) B has 5 electrons so B3+ has 2 electrons
(b) O has 8 electrons so O- has 9 electrons
(c) Cl has 17 electrons so Cl3+ has 14 electrons
(d) Ca has 20 electrons so Ca2+ has 18 electrons
(e) There is no element with symbol [T]