Question

A species of an element $A$ has a net charge of -1 and it has 18 electrons and 20 neutrons. Identify the correct statements.

• A. Its symbol will be ${}_{17}^{37}\text{A}$
• B. Its atomic number is 18
• C. The number of protons are 17
• D. Its mass number is 38

Answer 1

Answer: (A), (C)

Its symbol will be ${}_{17}^{37}\text{A}$
The number of protons are 17

$X$ has 18 electrons with a net charge of -1 which means it gained one electron. Hence no. of protons is $(18-1=)17.$ So the atomic no. will be 17. $X$ has 20 neutrons. Mass no. is the addition of protons and neutrons so the mass no. will be 37.

Its symbol will be ${}_{17}^{37}\text{X}.$