Naming of halogen group in ethane
In general nomenclature, the practice of omitting locants when there is no ambiguity is widespread. For preferred IUPAC names, however, the current recommendations given in Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) are prescriptive about when locants are omitted. In particular:

P-14.3.4.2 The locant ‘1’ is omitted:
(…)
(b) in monosubstituted homogeneous chains consisting of only two identical atoms;
(…)

Therefore, the preferred IUPAC name is indeed chloroethane and not the (correct, but not preferred) complete systematic name ‘1-chloroethane’.
(Nevertheless, note the correct capitalization and hyphenation of the names.)