What contribution to atomic theory resulted from Albert Einstein's work? O A. A new understanding of what caused some elements to be
radioactive
B. A new model of the atom that described electrons as being in a
cloud
C. The discovery that different numbers of neutrons produced
isotopes
O D. A new understanding that the nucleus contained protons and
neutrons

i would say b

explanation:

but i think i would need more information than that

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally