Friday, March 6, 2015

Element Identity

Midway through my teaching career our district offered a popular science course called Introductory Physical Science (IPS). One primary purpose was to introduce the concept that matter was composed of billions of tiny particles called atoms rather than a continuous homogeneous mass of matter. The particulate nature of matter is not visually obvious to observers. The concept of matter’s composition as discrete particles by ancient thinkers several thousand years ago was an early inspiration. But it remained for scientists during the modern scientific revolution several hundred years ago to discover the concept empirically rather than rationally as did the early thinkers.

For IPS and most other modern science courses, logical development of ideas takes precedence over mere rote learning of facts and terms. Model development is based on sequential experimental evidence. For example, one fascinating experiment on spectral analysis which helped identify a chemical “element” followed establishment of the model of an element based on a previous sequence of logical classroom experiments. Ideally, our modern classroom science students benefit from logic, reasoning skills, and proper laboratory procedures.

How does spectral analysis help identify one of the nearly 100 natural elements comprising all matter? There are dozens of ways to identify an element. Spectral analysis is but one way. First, we remind readers that electron structure of atoms of each element is arranged hierarchically—one more electron is added as each element number increases by one. Atomic number 8, oxygen: 8 electrons; Atomic number 47, silver: 47 electrons. In any element, the outer valence shell (now called a principal energy level) of electrons governs how the element combines with other elements by giving up, acquiring, or sharing electrons.

When elements receive energy from an outside source, their electrons are driven to a higher energy level. When electrons return to their normal energy level, the atoms of that element emit energy in the form of light or other energy. Electron configurations vary from one element to another, so the wave lengths of light energy emitted are different from one element to anther. Some elements’ atoms may produce mainly one visible wave length of light. For example, sodium emits mainly orange light but manganese emits spectral light of many colors. The idea of an identifying “fingerprint” seems outdated, but it provides a scientifically useful analogy.

Spectroscopic analysis is based on the analysis of light coming from heated elements or compounds containing those elements. Each element emits characteristic patterns of spectral lines. In the IPS laboratory we heated small amounts of a compound of various elements in a burner flame. Viewed through a simple device called a spectroscope with a slit at one end and a small piece of material called a diffraction grating at the other, we observed one or more bright spectral lines. Simple science class spectroscopes for students are precursors of more advanced devices.

Spectral lines are unique to every element. Our sun produces the total visible spectrum because it possesses most elements in various quantities. Visible white light may be separated into every color from red to orange to yellow to green to blue and finally, violet. Visible red is produced by the longest physical light wavelengths. Violet is visible from the shortest wavelengths. Our sense of wonder is piqued when we understand that each separate position on the visible light spectrum may be produced by the action of electrons as they return to a previous energy level (ground state) in their “host” atom.

We close with an analogy from the world of bioscience. In the area of human life, a term stands out—biometrics. This technology can be used to discover an individual’s unique identity. There are many ways to identify a human’s unique identity. Likewise, in the world of physical science, there are many ways to identify substances. We have discussed only one in this post—spectral analysis. Our God designed the cosmos and stamped it with HIS divine identity. In a small way the identity of the universe’s building blocks—elements—speaks of the Creator’s ordered plan for our universe.

Searching for descriptions of the Introductory Physical Science (IPS) course, we encountered course descriptions from individual high schools as well as statements from the publisher. One statement from a Christian Brothers High School syllabus stood out. It read, “Additionally, the student will be working in teams during this course building moral values and a love of God. Science and spirituality are certainly not mutually exclusive.” The phenomena of our world are ordered because the God of Creation is the author of all things. Wonderful cause and effect events inspire humble worship of the Creator.