The atomic and mass numbers for four different atoms are given below. Which two are isotopes of the same element?

Question

anonymous · Answer

Atom    Atomic number     Mass number
a              100                       257
b              101                       257
c                101                      260
d              102                       259


 A and B

 B and C

 B and D

 C and D

ganeshie8 · Answer

which two atoms have same atomic number ?

anonymous · Answer

b and c

ganeshie8 · Answer

good  :) an element is uniquely identified by its atomic number, isotopes are just change in # of neutrons

anonymous · Answer

so the answer is b and c lol

ganeshie8 · Answer

same atomic number <=> same element

ganeshie8 · Answer

so u r correct !

anonymous · Answer

Thank you! (:

anonymous · Answer

@ganeshie8 i thought it was A and B...

anonymous · Answer

@phi @DebbieG

ganeshie8 · Answer

see my reply above :)

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same atomic number <=> same element

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anonymous · Answer

i saw..

anonymous · Answer

but I still don't get this subject

anonymous · Answer

its not just the same atomic number , it also has to be diff numbers of neutrons

ganeshie8 · Answer

you're absolutely correct

b              101                       257
c                101                      260

ganeshie8 · Answer

they both have same atomic number
different mass numbers implies, they have different number of neutrons

phi · Answer

Atomic number is the number of protons in the nucleus. Because atoms have an equal number of electrons as protons,  it is also the number of electrons.

As you know, the number of electrons determines the atom's chemical properties... which is how we tell different elements apart... they react differently, chemically speaking.
The atomic mass is how much the atom weighs, and it tells you how many protons and neutrons are in the nucleus.  

An atom with the same number of protons as another, but with a different number of neutrons will weigh a different amount.  But chemically (because they have the same number of electrons ) they are identical.   

So though they weigh different amounts, it almost never matters chemically, and we call them the same element.  But to show there is some difference, we call them isotopes.