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How to Calculate Wavelength with Amu

You can glean a great deal of information about chemical elements from the periodic table. For example, a given element's "atomic number"--its order in the table--reflects both its number of proton and electrons. You can use an element's position within the table to determine the amount of electrons that exist in its outermost shell and reflect its charge, or oxidation state. Another characteristic particular to each element is the wavelength of light it emits, which you can calculate using its velocity, its atomic mass in kilograms--converted from amu, or "atomic mass units"--and a common formula.

Calculator

Instructions

- 1
  Convert the atom's mass to grams, keeping in mind that 1 g = 6.022 x 10^23 amu. Argon, for example, has an atomic mass of 39.95 amu. In grams, this is 39.95/(6.022 x 10^23) = 6.634 x 10^-23 g.
- 2
  Multiple your atomic mass in grams by 1,000 to get it in kilograms, the units you'll need to calculate wavelength. For argon, this is 6.634 x 10^-23 * 1000 = 6.634 x 10^-20 kg.
- 3
  Plug your atomic mass in kilograms, alongside the atom's velocity, into the DeBroglie equation, λ = h/mv, where "h" is Planck's constant, or 6.6261 x 10&-34 J s-1. If the atom in question is moving at 3.0 x 10^5 m/s, then argon's wavelength is λ = (6.6261 x 10^-34)/(6.634 x 10^-20 kg * 3.0 x 10^5) = (6.6261 x 10^-34)/(1.99 x 10^-14) = 3.33 x 10^-20 meters.

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