1 Some overlaps will be seen to occur amongst the reactivity labels 2 The unclassified metals are generally H, C, N, O, P, S, and Se 3 a. For aluminium, ) write, "[It] is quite reactive, but a thin, transparent film of Al2O3 forms when Al comes into contact with air. This protects it from further oxidation. For this reason, it is even passive toward nitric acid (HNO3), a strong oxidizing agent. When the oxide coating is sanded off, Al reacts vigorously with HNO3." ) mentions that aluminium, tin and lead are widely used for their corrosion resistance. Thallium is unaffected by water or alkalis but is attacked by acids, and is slowly oxidized in room temperature air . b. Arsenic is stable in dry air. Extended exposure in moist air results in the formation of a black surface coating. "Arsenic is not readily attacked by water, alkaline solutions or non-oxidizing acids" . It can occasionally be found in nature in an uncombined form 91) It has a positive standard reduction potential (As → As 3+ + 3e = +0.30 V), corresponding to a classification of semi-noble metal . 4 The noble metals are a subset of d-block metals . The halogens range from highly reactive F to fairly reactive I; the unclassified nonmetals range from high (O) to low (N). Parish deals only with the metals; the match-ups to the four types of nonmetals are this author's contribution.