Final answer:
The element symbol for calcium is “Ca”, and the ion symbol when calcium gains two electrons is “Ca²+”. The element follows the English term for its chemical symbol and adheres to the octet rule to stabilize its outer electron shell.
Step-by-step explanation:
The symbol for the element calcium, which has the atomic number 20, is represented by the letters Ca. When an atom of calcium becomes an ion by gaining two electrons, it achieves a stable electron configuration. This results in a calcium ion with 18 electrons, 20 protons, and a net charge of +2, denoted as Ca²+.
Atoms strive to follow the octet rule, which seeks to fill their outer shell with eight electrons to attain stability, by donating, accepting, or sharing electrons. The chemical symbols for elements typically consist of a single capital letter or a combination of two letters. The symbol Ca for calcium follows the English name of the element.
In Lewis symbols, which are diagrams that represent the valence electrons of an atom, calcium is indicated as •Ca•. These symbols can also show the formation of cations, as demonstrated for both sodium and calcium.