In all the above cases the elements have united atom for atom. Some elements will not so unite. In CaCl2 how many atoms of each element? Parts by weight of each? Give molecular weight. Is the size of the molecule thereby changed? Name these, give the number of atoms of each element in the molecule, and the proportion by weight, also their molecular weights: AuCl3, ZnCl2, MnCl2, Na2O, K2S, H3P, H4C.
Principal Elements.
Name. Sym. At. Wt. Valence. Vap.D. At.Vol. Mol.Vol. State.
Aluminium Al 27. II, IV … … … Solid
Antimony Sb 120. III, V. … … … "
Arsenic As 75. III, V 150. "
Barium Ba 137. II … … … "
Bismuth Bi 210. III, V … … … "
Boron B 11. III … … … "
Bromine Br 80. I, (V) 80. Liquid
Cadmium Cd 112. II 56. Solid
Calcium Ca 40. II … … … "
Carbon C 12. (II), IV … … … "
Chlorine Cl 35.5 I, (V) 35.5 Gas
Chromium Cr 52. (II),IV,VI … … … Solid
Cobalt Co 59. II, IV … … … Gas
Copper Cu 63. I, II … … … "
Fluorine F 19. I, (V) … … … Gas
Gold Au 196. (I), III … … … Solid
Hydrogen H 1. I 1. Gas
Iodine I 127. I, (V) 127. … … Solid
Iron Fe 56. II,IV,(VI) … … … "
Lead Pb 206. II, IV … … … "
Lithium Li 7. I … … … "
Magnesium Mg 24. II … … … "
Manganese Mn 55. II, IV, VI … … … "
Mercury Hg 200. I, II 100. Liquid
Nickel Ni 59. II, IV … … … Solid
Nitrogen N 14. (I),III,V 14. Gas
Oxygen O 16. II 16. "
Phosphorus P 31. (I),III, V 62. Solid
Platinum Pt 197. (II), IV … … … "
Potassium K 39. I … … … "
Silicon Si 28. IV … … … "
Silver Ag 108. I … … … "
Sodium Na 23. I … … … "
Strontium Sr 87. II … … … "
Sulphur S 32. II,IV,(VI) 32(96) "
Tin Sn 118. II, IV … … … "
Zinc Zn 65. II 32.5 "
If more than one atom of an element enters into the composition of a binary, a prefix is often used to denote the number. SO2 is called sulphur dioxide, to distinguish it from SO3, sulphur trioxide. Name these: CO2, SiO2, MnO2. The prefixes are: mono or proto, one; di or bi, two; tri or ter, three; tetra, four; pente, five; hex, six; etc. Diarsenic pentoxide is written, As2O5. Symbolize these: carbon protoxide, diphosphorus pentoxide, diphosphorus trioxide, iron disulphide, iron protosulphide. Often only the prefix of the last name is used.
16. An Oxide is a Compound of Oxygen and Some Other Element, as HgO. What is a chloride? Define sulphide, phosphide, arsenide, carbide, bromide, iodide, fluoride.
In Experiment 6, where S and Fe united, the symbol of the product was FeS. Name it. How many parts by weight of each element? What is its molecular weight? To produce FeS a chemical union took place between each atom of the Fe and of the S. We may express this reaction, i.e. chemical action, by an equation:—
Iron + Sulphur = Iron Sulphide
Or, using symbols Fe + S = FeS
Using atomic weights, 56 32 = 88.
These equations are explained by saying that 56 parts by weight of iron unite chemically with 32 parts by weight of sulphur to produce 88 parts by weight of iron sulphide. This, then, indicates the proportion of each element which combines, and which should be taken for the experiment. If 56 g. of Fe be used, 32 g. of S should be taken. If we use more than 56 parts of Fe with 32 of S, will it all combine? If more than 32 of S with 56 of Fe? There is found to be a definite quantity of each element in every chemical compound. Symbols would have no meaning if this were not so.
Write and explain the equation for the experiment with copper and sulphur, using names, symbols, and weights, as above.