Physical Chemistry : Atomic Nucleus

Study concepts, example questions & explanations for Physical Chemistry

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Example Questions

Example Question #1 : Atomic Nucleus

How many neutrons are present in the nucleus of one atom of

Possible Answers:

Correct answer:

Explanation:

From the periodic table, we find that the atomic number, i.e., the number of protons in the nucleus of  is 15. Given that the mass number is 32, and recalling the formula which relates mass number to the number of neutrons and protons: , we find that the number of neutrons in the nucleus of one atom of  is 17.

Example Question #95 : Physical Chemistry

Which atomic symbol represents a period five transition metal that has 42 electrons when it forms a  cation? 

Possible Answers:

Correct answer:

Explanation:

Transition metals extend from groups 3 through 12 and periods 4 through 7. Ru, in its neutral state, has 44 electrons. Therefore, when it becomes a  cation, it will have 42 electrons. 

Example Question #96 : Physical Chemistry

What is the mass number, atomic number, and charge, of the isotope of an atom that contains 34 protons, 36 neutrons, and 36 electrons?

Possible Answers:

Mass number: 

Atomic number: 

Charge: 

Mass number: 

Atomic number: 

Charge: 

Mass number: 

Atomic number: 

Charge: 

Mass number: 

Atomic number: 

Charge: 

Mass number: 

Atomic number: 

Charge: 

Correct answer:

Mass number: 

Atomic number: 

Charge: 

Explanation:

The atomic number is equal to the number of protons in the element, so from the periodic table, we find that the element with atomic number 34 is selenium. Since , we calculate that the mass number is 70. Lastly, there are two more electrons than protons, so the charge will be .

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