Chemistry AAS

What happens when an electron absorbs energy in an atom?

An electron can jump to a higher energy level if it absorbs energy that corresponds to the difference between the lower and higher energy levels.

How can heat from a Bunsen Burner flame affect electrons in metal atoms?

The heat provides sufficient energy for electrons to jump to higher energy levels.

What occurs when excited electrons return to lower energy levels?

They emit the energy they had absorbed, which is often seen as colored light.

What determines the wavelength and color of the emitted light from excited electrons?

The energy of the light emitted which is equal to the difference between the two energy levels.

What is an emission spectrum?

It is a series of colored lines produced when emitted light is passed through a prism, separating it into different wavelengths.

Why is each element's emission spectrum unique?

No two elements have energy levels of exactly the same energy due to different numbers of protons, making their spectra characteristic.

What is Atomic Absorption Spectroscopy (AAS)?

A highly sensitive and selective quantitative analytical technique used to determine the concentration of metallic elements in a sample.

What is the first stage of Atomic Absorption Spectroscopy?

A hollow cathode lamp is selected, containing a cathode coated with the element of interest, and a voltage is applied to excite outer shell electrons.

What happens to the emitted photons in the first stage of AAS?

Photons of specific energies and wavelengths are released when electrons transition to lower energy levels.

What occurs in the second stage of Atomic Absorption Spectroscopy?

A nebuliser system draws up the sample, which is then aspirated into the flame, evaporating the solvent and breaking down compounds into free atoms.

How do atoms in the flame interact with the incident beam in AAS?

Atoms and ions absorb available energies from the incident beam if they contain matching transitions.

What is the role of the monochromator in the third stage of AAS?

It separates the transmitted beam into individual wavelengths, selecting one unique to the element under investigation.

What mathematical relationship is used to determine absorbance in AAS?

A = ε × l × c, where A is absorbance, ε is the molar attenuation coefficient, l is path length, and c is concentration.

What is the absorption spectrum?

It is produced when white light passes through a vapor of metal, with electrons absorbing certain frequencies, resulting in a continuous spectrum with black lines.

How does the absorption spectrum relate to the emission spectrum?

The absorption spectrum is the opposite of the emission spectrum for that element.

What happens to the absorbed energy in an absorption spectrum?

The absorbed energy is immediately radiated as electrons return to their ground state, but it is radiated in all directions.

What is the significance of the black lines in an absorption spectrum?

They correspond to the wavelengths of light that were absorbed by the electrons.

What does the term 'ppm' refer to in the context of AAS?

Parts per million, a unit of measurement for concentration.

What does 'ppb' stand for in AAS?

Parts per billion, another unit of measurement for concentration.

What is the purpose of using a hollow cathode lamp in AAS?

To provide a source of light specific to the element being analyzed.

What is the effect of the flame's high temperature in AAS?

It quickly evaporates the solvent and breaks down compounds to free atoms and ions.

What is the outcome if the element of interest is present in the sample during AAS?

All transitions will match, leading to atomic absorption followed by emission.

Why is the intensity of the transmitted beam compared to the incident beam in AAS?

To determine the absorbance and thus the concentration of the element under investigation.