Question

the table below gives information about two isotopes of element y.

1. 3 **calculate the average atomic mass of element y to the appropriate number of significant figures. show all work.
2. 1 **what is the identity of element y?
3. 1 **what is the atomic number of element y?
4. 2 write the isotope name and isotopic symbol for isotope 3.

Explanation:

Step1: Calculate contribution of isotope 1

Multiply mass of isotope 1 by its relative abundance.

$$19.99\times\frac{90.48}{100}=19.99\times0.9048 = 18.076952$$

Step2: Calculate contribution of isotope 2

Multiply mass of isotope 2 by its relative abundance.

$$20.99\times\frac{0.27}{100}=20.99\times0.0027= 0.056673$$

Step3: Calculate contribution of isotope 3

Multiply mass of isotope 3 by its relative abundance.

$$21.99\times\frac{9.25}{100}=21.99\times0.0925 = 2.034075$$

Step4: Sum up contributions

Add the contributions of all three isotopes.

$$18.076952+0.056673 + 2.034075=20.1677$$

Answer:

The average atomic mass of element \(Y\) is \(20.17\) (rounded to four significant figures).