diferencias entre el papo y la pepa

Texto 5
The Atom

Composition of atomic nuclei
Atomic nuclei consist of combinations of protons, or positively-charged particles, and neutrons, or uncharged particles. The number of protons andneutrons in each element can vary, but only certain combinations are stable. For example, Calcium-48, having 20 protons and 28 neutrons, is a stable isotope of Calcium. But if there is an excessor deficiency of neutrons in any combination, the isotope will be unstable. A nucleus is more likely to be unstable if it is a heavy one—that is, if it contains a large number of protons and neutrons.Unstable nuclei attempt to achieve stability by emitting some form of radiation, until they transform themselves into stable isotopes.

Isotopes
All atoms of a particular element have the same number ofprotons in the nuclei. However, not all the atoms of some elements contain the  same number of neutrons, and in nature, a given element will have various forms each with a different numberof neutrons. Additional neutrons do not add any charge to the nucleus of an atom, but rather increase its atomic mass, leaving the atom with the same atomic number. Such forms of the same element are known asisotopes.

Further characteristics of an isotope
Sometimes an isotope of an element has a further characteristic. It is unstable and ―decays‖ into another isotope. In the case of the heavier elementsespecially, an isotope of one element decays into another element altogether. For example, an atom of the radioactive element uranium-238 decays first into an atom of thorium-234 with 
the releaseof an alpha particle (2 protons and 2 neutrons is generally called an alphaparticle), which  has a mass of 4. The decay of one isotope into another takes a constant amount of time for each element. Thetime it takes for half of the isotope to break down is called its half-life. One element‘s half life may be a few seconds while 
another‘s may be a million of years.

Texto 5
El átomo...