Question

question 15
what is the most massive part of an atom?
protons
area outside the nucleus
nucleus
neutrons
question 16
1 pts
an atom of strontium has at least four different isotopes. what is different between an isotope of ⁸⁶sr and an isotope of ⁸⁷sr?
one proton
one orbital
one electron
one neutron

Explanation:

For Question 15: The nucleus contains protons and neutrons. Protons and neutrons have much more mass than electrons. Since the nucleus is made up of these relatively massive particles, it is the most massive part of the atom.
For Question 16: Isotopes of the same element have the same number of protons (which defines the element). They differ in the number of neutrons. The numbers 86 and 87 in \(^{86}Sr\) and \(^{87}Sr\) are mass - numbers (sum of protons and neutrons). Since the element is the same (strontium), the number of protons is the same, and the difference lies in the number of neutrons.

Answer:

Question 15: C. nucleus
Question 16: D. one neutron