If a species has 11 protons, 12 neutrons and 10 electrons then (i) what is its atomic number and mass number? (ii) is it neutral, a cation or an anion? Explain. (iii) write its electronic configuration. (iv) name the species.
Atomic number = 11, Mass number = 23
Cation, because it has 11 protons and 10 electrons, resulting in a net positive charge (+1).
2, 8
Sodium ion (Na⁺)
Explanation
(i) The atomic number of a species is equal to its number of protons. Here, it is 11. The mass number is the sum of protons and neutrons, which is 11 + 12 = 23.
(ii) The species is a cation. A neutral atom has an equal number of protons and electrons. Here, the number of protons (11) is greater than the number of electrons (10). The loss of one electron gives the species a net positive charge of +1, which makes it a cation.
(iii) The species has a total of 10 electrons. The electronic configuration is written by distributing these electrons into shells. The first shell holds 2 electrons, and the remaining 8 electrons go into the second shell. Thus, the configuration is 2, 8.
(iv) An element with atomic number 11 is sodium. As the sodium atom loses its single valence electron to attain a stable octet configuration and becomes a positively charged ion, the species is named sodium ion (Na⁺).