Two isotopes of copper occur naturally:

isotopes of copper: percent abundance: atomic mass:
copper - 63 69.17 % 62.9396 amu
copper - 65 30.83 % 64.9278 amu
calculate the average atomic mass for the two isotopes of copper. answer to 4 decimal places.

Average atomic mass of copper = 63.5525 amu.

Explanation:

Abundance of Cu⁶³ = 69.17%

Abundance of Cu⁶⁵ = 30.83%

Atomic mass of Cu⁶³ = 62.9396 amu

Atomic mass of Cu⁶⁵ = 64.9278 amu

Average atomic mass = ?

Solution:

Average atomic mass of copper = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass of copper= ( 62.9396×69.17)+(64.9278×30.83) /100

Average atomic mass of copper=  4353.5321 + 2001.7240 / 100

Average atomic mass of copper = 6355.2561 / 100

Average atomic mass of copper= 63.5525 amu.

indium, and thallium have three electrons i think