Isotopes vs Elements
Similar type of atoms can be changed slightly to form different isotopes. An element may have several isotopes. The nature of each isotope contributes to the nature of an element. Following is a broad explanation about elements and isotopes.
We are familiar with the word “element,” because we learn about them in the periodic table. There are about 118 elements in the periodic table, and they are arranged according to their atomic number. An element is a chemical substance, which consists of only a single type of atoms, hence they are pure. For example, the smallest element is hydrogen. Silver, gold, platinum are some of the commonly known precious elements. Each element has an atomic mass, atomic number, symbol, electronic configuration, etc. Although, most of the elements are naturally occurring, there are some synthetic elements like Californium, Americium, Einsteinium, and Mendelevium. All the elements can be broadly categorized into three; as metal, metalloids and non metals. Further, they are categorized into groups and periods based on more specific characteristics. Elements in the same group or periods share certain common characteristics, and some properties may change sequentially when you go through a group or period. Elements can be subjected to chemical changes to form various compounds; however, elements cannot be further broken down by simple chemical methods.
Atoms of the same element can be different. These different atoms of the same element are called isotopes. They are different from each other by having a different number of neutrons. Since the neutron number is different, their mass number also differs. However, the isotopes of the same element have the same number of protons and neutrons. Different isotopes present in varying quantities, and this is given as a percentage value called relative abundance. For example, hydrogen has three isotopes as protium, deuterium and tritium. Their number of neutrons and relative abundances are as follows.
1H – no neutrons, relative abundance is 99.985%
2H- one neutron, relative abundance is 0.015%
3H- two neutrons, relative abundance is 0%
The number of neutrons a nucleus can hold differs from element to element. Among these isotopes, only some are stable. For instance, oxygen has three stable isotopes, and tin has ten stable isotopes. Most of the time, simple elements have same neutron number as the proton number. But in heavy elements, more neutrons are there than the protons. The number of neutrons is important to balance the stability of the nuclei. When the nuclei are too heavy, they become unstable and therefore, those isotopes become radioactive. For example, 238U emits radiation and decays to much smaller nuclei. Isotopes may have different properties because of their different masses. For example, they may have different spins, thus their NMR spectra differs. However, their electron number is similar giving rise to a similar chemical behavior.
A mass spectrometer can be used to get information about isotopes. It gives the number of isotopes, which an element has, their relative abundances, and masses.
What is the difference between Isotopes and Elements?
- Different atoms of the same element are called isotopes.
- Each element can have several isotopes.
- The atomic weight of the element differs from the isotopic mass. The abundance of each isotope determines the atomic weight of an element.