Atomic mass unit

The unified atomic mass unit (symbol: u) or dalton (symbol: Da) is the standard unit that is used for indicating mass on an atomic or molecular scale (atomic mass). One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is equivalent to 1 g/mol. It is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of 6973166053892199999♠1.660538921(73)×10⁻²⁷ kg. The CIPM has categorised it as a non-SI unit accepted for use with the SI, and whose value in SI units must be obtained experimentally.

The amu without the "unified" prefix is technically an obsolete unit based on oxygen, which was replaced in 1961. However, some sources may still use the term "amu" but now define it in the same way as u (ie. based on carbon-12). In this sense, most uses of the terms "atomic mass units" and "amu" today actually refer to unified atomic mass units. For standardization a specific atomic nucleus (carbon-12 vs. oxygen-16) had to be chosen because average mass of a nucleon depends on the count of the nucleons in the atomic nucleus due to mass defect. This is also why the mass of a proton (or neutron) by itself is more than (and not equal to) 1 u.

Atomic mass unit does not stand for the unit of mass in the atomic units system, which is rather m _e.

1. Explain the following formula:

1. Write definitions of the following terms: dalton, wave, atomic orbital, photon, atomic spectral lines.

Физика және математика кафедрасының отырысында қаралып, бекітілген.

Хаттама № «7» __18_____ ____03______ 2015 ж.

Кафедра меңгерушісі:____________ Кульжумиева А.А.

Факультеттің ОӘК отырысында қаралып, бекітілген.

Хаттама № «7» __19____ ____03_____ 2015 ж.

Факультеттің ОӘК төрағасы: _________ Иксебаева Ж.С.

М. Өтемісов атындағы Батыс Қазақстан мемлекеттік университеті

Факультет: физика-математика

Кафедра: физика және Физика

Шифр, мамандық: 5В011000 – Физика

Пән: Кәсіби бағытталған шетел тілі

Билет №10

1. Read and retell the text: