Question

How many protons, neutrons and electrons are in ${}^{39}{K_{19}}^{+}$?

Answer 1

Hint: Potassium is a chemical element represented by the symbol $K$having atomic number 19. It is a silvery grey metal which is soft enough to cut with a knife. It reacts rapidly with oxygen present in the atmosphere so it is kept in water.

Complete step by step answer:
An atom is composed of proton and neutron whereas protons are positively charged molecules and neutrons are neutral in nature i.e. carries no charge and electrons which are negatively charged ions are revolving around the nucleus. Protons are represented by the symbol $p$, electrons are represented by $e$whereas neutrons are represented by the symbol $n$.
The atomic number represents the number of protons and we know that atomic number of $K$i.e. potassium is 19, therefore number of protons in ${}^{39}{K_{19}}^{+}$ is 19. Number of neutrons can be calculated by subtracting the number of protons through its mass number. Mass number of potassium is 39, therefore the number of neutrons will be equal to $39-19=20$, hence number of neutrons in ${}^{39}{K_{19}}^{+}$is 20. Number of electrons is similar to the number of protons in a neutral atom but the given substance carries a positive charge which represents loss of electrons i.e. 1 electron is lost in this substance, therefore the number of electrons will be $19-1=18$.
Hence, we can say that there are 19 protons, 20 neutrons and 18 electrons are present in ${}^{39}{K_{19}}^{+}$.

Note: The mass of proton is taken as one unit and equals the mass of neutron, mass of neutron is also one unit and equals to the mass of protons whereas mass of electrons is about 1/2000 times the mass of hydrogen atom.