{"content":{"sharePage":{"page":0,"digests":[{"id":"13012939","dateCreated":"1246252491","smartDate":"Jun 28, 2009","userCreated":{"username":"kaicong123","url":"https:\/\/www.wikispaces.com\/user\/view\/kaicong123","imageUrl":"https:\/\/ssl.wikicdn.com\/i\/user_none_lg.jpg"},"monitored":false,"locked":false,"links":{"self":"https:\/\/liewsg.wikispaces.com\/share\/view\/13012939"},"dateDigested":1532092323,"startDate":null,"sharedType":"discussion","title":"Mole","description":"Well, to continue with Zhi Xian's point:
\nAtomic mass is the mass of one atom of an element only and the way we find it is through bombarding it into positive ions and checking out their angles of deflection, which is determined by charge over mass ratio.
\nHowever, as we all know that we are not able to count atoms one by one as there are so many and we cannot weigh them individually, clever scientists agreed upon a chemical quanitity known as "mole" and using it we discover that the the relative atomic mass of an element is the same as the gram of particles per mole or g\/mol.","replyPages":[{"page":0,"digests":[{"id":"13012985","body":"good, kaicong, go find out what is the quantity of one mole and how Avogadro derive that huge number :-) Mrs. Liew","dateCreated":"1246252950","smartDate":"Jun 28, 2009","userCreated":{"username":"Liewtsg","url":"https:\/\/www.wikispaces.com\/user\/view\/Liewtsg","imageUrl":"https:\/\/www.wikispaces.com\/user\/pic\/1246002418\/Liewtsg-lg.jpg"}}],"more":0}]},{"id":"13011329","dateCreated":"1246245205","smartDate":"Jun 28, 2009","userCreated":{"username":"chinzhixian","url":"https:\/\/www.wikispaces.com\/user\/view\/chinzhixian","imageUrl":"https:\/\/ssl.wikicdn.com\/i\/user_none_lg.jpg"},"monitored":false,"locked":false,"links":{"self":"https:\/\/liewsg.wikispaces.com\/share\/view\/13011329"},"dateDigested":1532092323,"startDate":null,"sharedType":"discussion","title":"Discussion Questions","description":"1) Derivation of Atomic Mass
\n
\nAtomic mass is derived through a method which is known as mass spectrometry.
\n
\n1. a sample is loaded onto the mass spectrometry instrument, and
\n2. the components of the sample are ionized by one of a variety of methods (e.g. impacting them with an electron beam), which results in the formation of charged particles (ions)
\n3. directing the ions into an electric and\/or magnetic field
\n4. computation of the mass-to-charge ratio of the particles based on the details of motion of the ions as they transit through electromagnetic fields, and
\n5. detection of the ions, which in step 4 were sorted according to mass-to-charge ratio
\n
\nBy Newton's second law of motion, lighter ions get deflected by the magnetic force more than heavier ions. The streams of sorted ions pass from the analyzer to the detector, which records the relative abundance of each ion type. This information is used to determine the chemical element composition of the original sample and the isotopic composition of its constituents.
\n
\n
\n
\n
\n2) "atomic mass" vs "relative atomic mass"
\n
\nAtomic mass is the total mass of protons, neutrons and electrons in a single atom (and only one atom), while relative atomic mass is the average mass per atom of the element\/isotope to the nearest 1\/12 of a carbon-12 atom.","replyPages":[{"page":0,"digests":[{"id":"13012971","body":"zhixian, well done:-)
\npt 2) relative atomic mass of atom is compared with 1\/12 of the mass of one carbon-as atom. Thats why relative atomic mass has no unit.
\npt 1) your last paragraph--the deviation of ions from the straight path is due to the resultant force caused by the interaction between the magnetic fielf generated by the moving ions and the magnetic field present in the spectrometer. - It is an electromagnetic effect. The smaller the mass, the greater the deflection. But the Newton's second law of F=ma you quoted is for circular motion, hence no change in magnitude of accelecration, only the direction. as force is a vector. - What I am trying to tell you is that we can not use Newton's second law[F=ma]to explain the deflection of ions directly, but rather indirectly...","dateCreated":"1246252836","smartDate":"Jun 28, 2009","userCreated":{"username":"Liewtsg","url":"https:\/\/www.wikispaces.com\/user\/view\/Liewtsg","imageUrl":"https:\/\/www.wikispaces.com\/user\/pic\/1246002418\/Liewtsg-lg.jpg"}}],"more":0}]}],"more":false},"comments":[]},"http":{"code":200,"status":"OK"},"redirectUrl":null,"javascript":null,"notices":{"warning":[],"error":[],"info":[],"success":[]}}