Question

indium (in) is made up of 95.7% 115 in and 4.3% 113 in. the atomic mass of 113 in is 112.904 amu. the atomic mass of 115 in is 114.904 amu. what is the average atomic mass of a sample of indium?
114.5 amu
114.818 amu
115.00 amu
113.909 amu
question 18
1 pts
an atom has 24 protons and 12 neutrons. what is the chemical symbol for the atom? use the periodic table.
cr
k
ca
mg

Explanation:

Step1: Calculate contribution of 115 In

Multiply the atomic mass of 115 In by its percentage.
$114.904\times0.957 = 109.953128$

Step2: Calculate contribution of 113 In

Multiply the atomic mass of 113 In by its percentage.
$112.904\times0.043=4.854872$

Step3: Find average atomic mass

Add the two contributions together.
$109.953128 + 4.854872=114.808\approx114.818$

The atomic number is equal to the number of protons. An atom with 24 protons has an atomic number of 24. Looking at the periodic - table, the element with atomic number 24 is Chromium, which has the chemical symbol Cr.

Answer:

114.818 amu