Question

42 Nuclear Physics 42.1 Nuclear Structure 1. Consider the atoms 10, 180, 185, 18Ne, and 20Ne. Some of the questions about these atoms may more than one answer. Give all answers that apply. a. Which atoms are isotopes? b. Which atoms are isobars? c. Which atoms have the same chemical properties? d. Which atoms have the same number of neutrons? e. Which atoms have the same number of valence electrons? f. Rank in order, from largest to smallest, the radii of the nuclei of these atoms.

Answer 1

(a) Isotopes are atoms of the same element with similar atomic number but different atomic mass.

Among the given elements isotopes are

¹⁶O and ¹⁸O ; and ¹⁸Ne and ²⁰ Ne

(b) Isobars are the atoms of different elements with same mass number but different atomic number.Thus isobars are

¹⁸O, ¹⁸F and ¹⁸Ne

(c) Isotopes share same chemical properties because chemical properties are determined by the atomic number which is same in case of isotopes.

Therefore elements having the same chemical properties are

¹⁶O and ¹⁸O ; and ¹⁸Ne and ²⁰Ne

(d) To calculate the number of neutrons, we need to subtract the number of protons from the mass number.

For ¹⁶O: number of neutrons=16-8 = 8

For ¹⁸O: number of neutrons=18-8 = 10

For ¹⁸F: number of neutrons=18-9 = 9

For ¹⁸Ne: number of neutrons=18-10 = 8

For ²⁰Ne: number of neutrons=20-10 = 10

Therefore atoms ¹⁶O and ¹⁸Ne have same number of neutrons and atoms ¹⁸O and ²⁰Ne have same number of neutrons.

(e) Since isotopes have the same atomic number, i.e., same number of electrons. Therefore isotopes will have the same number of valence electrons as well.

Thus the atoms having the same number of valence electrons are

¹⁶O and ¹⁸O; and ¹⁸Ne and ²⁰Ne

(f) The radii of the nuclei of these atoms are arranged from largest to smallest as

²⁰Ne > ¹⁸Ne > ¹⁸F > ¹⁸O > ¹⁶O