By: Morgan, Haley, and LeAnna Identifying Elements By: Morgan, Haley, and LeAnna

All protons are alike, regardless of the atom being considered. Neutrons and electrons are the same. So what makes them different?

Atomic Number Each element is given an atomic number. The atomic number is the same as the number of protons in the atom. No atom has the same amount of protons so therefore each atomic number for each element is unique. The number of protons is also equal to the number of electrons so the atomic number can tell us the amount of electrons in the atom.

Atoms of different elements are composed of different numbers of protons, neutrons, and electrons. All we really need to know to identify a particular element is its atomic number, mass number, and atomic weight. These indicators provide an almost complete picture of each element.

Atomic Mass Number The atomic mass number is the sum of the protons and neutrons contained in its nucleus. The mass of the electrons is so small that it is just ignored.

Atomic Weight and Isotopes Isotopes have the same number of protons and electrons but vary in the number of neutrons they contain. Isotopes of an element have the same atomic number but have different atomic masses. Because all of an element’s isotopes have the same number of electrons, their chemical properties are exactly the same. The atomic weight of any element is approximately equal to the mass number of its most abundant isotope.

The heavier isotopes of certain atoms are unstable and tend to decompose to become more stable; such isotopes are called radioisotopes. This process is very complex. The “glue” that holds the atomic nuclei together is weaker in the heavier isotopes. The process of spontaneous atomic decay is called radioactivity and it can be compared to a tiny explosion. All types of radioactive decay involve the ejection of particles or electromagnet energy from the atom’s nucleus and are damaging to living cells.

Alpha emission has the least penetrating power; gamma radiation has the most. Ionizing radiation does not damage the atoms in its path directly.

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