Question

Which of the following atoms will have the same number of electrons, protons and neutrons?

• A. ${}_6{}^{12}C$
• B. ${}_{11}{}^{23}Na$
• C. ${}_{15}{}^{31}P$
• D. ${}_{17}{}^{35}Cl$

Answer 1

The correct option is A

${}_6{}^{12}\mathrm{C}$

An atom can be represented as ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ , where X is the symbol of the atom, A represents the mass number (sum of the number of protons and neutrons) and Z represents the atomic number (number of protons). In an electrically neutral atom, the number of protons is equal to the number of electrons.

${}_6{}^{12}\mathrm{C}$ - Z = 6, number of protons = 6, number of electrons = 6

A = 12, neutrons + protons = 12

neutrons + 6 = 12

neutrons = 12 - 6 = 6

Hence, option (a) ${}_6{}^{12}\mathrm{C}$ atom has the same number of electrons, protons, and neutrons.

Symbol	number of protons	number of electrons	number of neutrons
${}_6{}^{12}\mathrm{C}$	6	6	6
${}_{11}{}^{23}\mathrm{Na}$	11	11	12
${}_{15}{}^{31}\mathrm{P}$	15	15	16
${}_{17}{}^{35}\mathrm{Cl}$	17	17	18