Chemical element of metals. Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by a period (full stop) as with abbreviations. Later chemical elements were also assigned unique chemical symbols, based on the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' after the Latin "natrium". The same applies to "W" (wolfram) for tungsten, "Fe" (ferrum) for iron, "Hg" (hydrargyrum) for mercury, "Sn" (stannum) for tin, "K" (kalium) for potassium, "Au" (aurum) for gold, "Ag" (argentum) for silver, "Pb" (plumbum) for lead, "Cu" (cuprum) for copper, and
Au pair for a residence permit for this purpose. Au pairing has long been a favored way for young women to learn French and, increasingly, for young men as well. The pocket money for au pairs in France is Euro 60 per week, plus, in most cases, a 20 euro a week contribution to language classes; in Paris families may also provide a carte Navigo (urban travel pass) which is worth 95 euros (approximately). Enrollment in a French language course is compulsory for non-European au pairs. While France does not have an official, government sponsored Au Pair Program, a number of established