some isotopes of elements are unstable and decay into other, more stable isotopes over time. for example, it takes 153 years for half of a sample of silicon (si) atoms with 14 protons, 14 electrons, and 18 neutrons to decay.

what is the name of this specific silicon isotope?

silicon-32

Explantion:   Silicon is a chemical element that has atomic number 14 and is located in group 14 in the periodic table. Silicon has 23 recognized isotopes, with mass numbers from 22 to 44. The oldest lived radioisotope is Silicon-32, and its half-life has been examined to be around 150 years. Silicon-32 is formed in the atmosphere by cosmic ray spallation of argon and is released on the surface of the earth in precipitation.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.