Question

The elements which have same number of nucleons but different number of protons are known as :

• A. isobar
• B. isotope
• C. isotone
• D. none of these

Answer 1

Answer: (A)

Nucleon = number of $(p+n)=$ mass number Atomic number $=$ number of proton Atom of different elements having same mass number (i.e., same number of $p+n$) but different number of $p$ (at number) are called isobars, e.g., ${}_6{C}^{14}{,}_7{N}^{14}.$
Atoms of same element having same number of $p$ (same atomic number but different mass number i. e., different number of neutrons) are called isotopes e.g., ${}_1{H}^1,{}_1{H}^2,{}_1{H}^3$ are isotopes of hydrogen.
Atoms of different element having same number of neutrons are called isotones.
e.g., ${}_6{C}^{13},{}_7{N}^{14}$
$=$ Number of neutrons
$=14-7=7$
number of neutrons $=13-6=7$