Question

1. is it correct or incorrect in science to define a theory as someone’s best guess about an aspect of nature? explain your answer.

1. what evidence convinced j.j. thomson that an atom consists of more than electrons?

1. what feature of rutherford’s gold foil experiment was most surprising to those who carried out the experiment?

1. could two isotopes of an element have different numbers of protons? explain.

1. the element boron has two isotopes, with mass numbers of 10 and 11. the abundance of the two isotopes is 20 percent and 80 percent, respectively. without making a mathematical calculation, estimate the atomic mass of boron.

Explanation:

Question 20

In science, a theory is not a guess. It's a well - supported, comprehensive explanation of natural phenomena, backed by extensive evidence and testing (e.g., cell theory, theory of evolution). A guess is a hypothesis, a tentative explanation. So defining a theory as a best guess is incorrect.

J.J. Thomson knew atoms are neutral (no net charge). He discovered electrons (negative charge). So an atom must have positive charge to balance electrons, meaning it has more than just electrons (there must be positive - charged matter too).

In Rutherford's gold foil experiment, most alpha particles passed through (expected), but some were deflected at large angles or even bounced back. This was surprising because the plum - pudding model (prevailing theory) suggested atoms were diffuse, so alpha particles should pass through easily. The large - angle deflections implied a small, dense, positive - charged nucleus.

Answer:

Incorrect. A scientific theory is a well - substantiated, comprehensive explanation of natural phenomena, supported by extensive evidence (like experiments, observations). A "best guess" is a hypothesis, a tentative idea to be tested, not a theory.

Question 21