Question

1. decide if the following are isotopes (yes or no)

____no a) 8 protons and 9 neutrons
8 protons and 8 neutrons
yes____
d) si - 15 and p - 15
_no____ b) 5 protons and 6 neutrons
6 protons and 6 neutrons
____ e) 25 p⁺ and 30 n⁰
25 p⁺ and 33 n⁰
____ c) ⁸⁰₃₈sr ⁸¹₃₈sr ⁸³₃₈sr

1. how are uranium - 238 and uranium - 235 similar? different?

Explanation:

Step1: Recall isotope definition

Isotopes are atoms of the same element with different numbers of neutrons. Elements are defined by the number of protons.

Step2: Analyze part a

The first has 8 protons (oxygen - 17 as 8 + 9 = 17 mass - number) and the second has 8 protons (oxygen - 16 as 8+8 = 16 mass - number). They are isotopes of oxygen. So the answer is yes.

Step3: Analyze part b

The first has 5 protons (boron) and the second has 6 protons (carbon). Different elements, so not isotopes. Answer is no.

Step4: Analyze part c

All have 38 protons (strontium). Different mass - numbers ($^{80}_{38}Sr$, $^{81}_{38}Sr$, $^{83}_{38}Sr$) due to different numbers of neutrons. They are isotopes. Answer is yes.

Step5: Analyze part d

Si has 14 protons and P has 15 protons. Different elements, so not isotopes. Answer is no.

Step6: Analyze part e

Both have 25 protons (manganese). First is Mn - 55 (25 + 30) and second is Mn - 58 (25+33). They are isotopes. Answer is yes.

Step7: Analyze uranium - 238 and uranium - 235

Similarity: Both are isotopes of uranium, so they have the same number of protons (92).
Difference: Uranium - 238 has a mass - number of 238 and uranium - 235 has a mass - number of 235. So they have different numbers of neutrons (238 - 92=146 for U - 238 and 235 - 92 = 143 for U - 235).

Answer:

a) yes
b) no
c) yes
d) no
e) yes

1. Similar: Same number of protons (92). Different: Different number of neutrons (146 in U - 238 and 143 in U - 235)