# Physical Constants, Properties, Mathematical Calculations and Equations

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## Essay title: Physical Constants, Properties, Mathematical Calculations and Equations

• Emission

• There are two significant effects of contamination by metal ions:

1. Salinity: When metal ion concentrations are too high and exceed safe limits. High salinity water is unsuitable for drinking or irrigation purposes.

2. Toxicity: Can occur even with extremely low concentrations of metal ions. These ions are often called heavy metal ions because their density are five times greater than that of water.

• Atomic emission occurs when electrons are energetically promoted by the absorption of energy to an excited state from its ground state.

• An emission spectrum is a graph with intensity of light plotted against wavelength (nm). All metals have a characteristic emission wavelength.

• Consider the three possible electron transitions for a sodium ion. Ground state of Na is [Ne] 3s1. The valence electron can be promoter to any one of several excited states. It will usually jump to the next lowest energy level when heated in a flame. The electron configuration for a sodium ions 3s to 3p is represented as *[Ne] 3p1.

• After a short period of time, the electron loses that energy by emitting it in the form of light. And emission spectrum can be recorded for the process.

• To determine the energy emitted by the transition of an electron, we must know either wavelength (&#955;) or frequency (&#957;). The wavelength is related to the frequency and the speed of light (c) by the following equation with the speed of light constant 3.00 x 108m/s.

o c = &#955; &#957;

• The energy, E, of the emitted light is the product of Planck’s constant, h = 6.63 x 10-34 J, and the frequency of light, &#957;.

o E = h &#957;

• When we combine equations 1 and 2, we can relate energy and wavelength.

o &#957; = c/ &#955;

o E = hc/ &#955;

• Using our energy equation, we can calculate the energy of a photon of light emitted by an electron in a sodium atom that is moving from an excited to a ground state with a wavelength of 589 nm.

o

• From there, we can calculate the energy emitted by 1 mole of Na atoms.

o

• Absorption

• Variables Defined:

o P0 = the power of the light immediately after it passes through the first wall of the sample container.

o P = the power of the light after it has passed the sample.

o P1, P2 = The power of the light immediately before entering the sample container and immediately after exiting the container respectively.

• Absorption spectroscopy is only interested in the

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