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.

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).