Question

What are the correct number of electrons protons and neutrons respectively in $ {{O}^{2-}} $ ion of the isotope $ O $ ?

Answer 1

Hint :We know that by taking the help of Avogadro number. Multiply the number of electrons, protons and neutrons in one $ {{O}^{2-}} $ ion to the Avogadro number which is $ 6.022\times {{10}^{23}}. $ Also Oxygen has three stable isotopes, $ 99.76%,0.04% $ and $ 0.20%. $

Complete Step By Step Answer:
Let us firstly find out the number of electrons, protons and neutrons in one $ {}^{16}{{O}^{-2}} $ ion. A neutral $ _{8}^{16}{{O}^{-2}} $ which has eight electrons, protons and neutrons. Number of protons present in an atom of an element determines its atomic number. All atoms of the same element consist of the same number of protons or we can say all atoms of the same element have the same atomic number. Atomic number represents the number of protons in an atom
The oxide anion has a charge of $ 2- $ this means that it has gained two electrons from another element, such as sodium or magnesium. All oxide anions $ {{O}^{2-}} $ have eight protons and ten electrons. The number of neutrons depends on the isotope.
The mass number of each isotope is the sum of the protons and neutrons in the nucleus. It is also the number written as a superscript to the left of the isotopic symbol (e.g. $ 16O $ ). If we know the atomic number $ \left( 8 \right), $ we can subtract that from the mass number to determine the number of neutrons.
 $ Mass\text{ }number-atomic\text{ }number=number\text{ }of\text{ }neutrons $
By using the formula; we get $ [16-8=+8neutrons] $
 $ {}^{16}{{O}^{-2}} $ has $ 8 $ protons, $ 8 $ neutrons and $ 10 $ electrons.

Note :
Be careful while counting electrons basically. As the given species is an anion so the number of electrons will be more than that of a neutral atom which means the nuclei of its atoms have eight protons. A neutral oxygen atom also has eight electrons.