Question

q1 chemistry u2l8 mastery quiz 1 practice
prepwork part 1:
analyze the mass - spectrum data for an unknown element d below and answer question 1 - 5

1. how many isotopes are depicted in the mass spectrum data above?
2. which peak depicts the isotope with the greatest abundance in nature?
3. which peak depicts the isotope with the greatest number of neutrons?
4. what is the likely identity of element d?
5. what is the atomic number of element d?
6. how many electrons are contained in an au³⁺ ion?

a. 76
b. 79
c. 82
d. 197

1. a neutral atom with 6 electrons and 8 neutrons is an isotope of

a. carbon
b. silicon
c. nitrogen
d. oxygen

1. *all isotopes of a given element must have the same

a. atomic mass
b. mass number
c. atomic number
d. number of neutrons

1. what is the total number of electrons in a mg²⁺ ion?

a. 10
b. 2
c. 12
d. 24

1. a neutral k atom differs from a k⁺ ion in that the k atom has one

a. more electrons
b. less electron
c. more proton
d. less proton

1. use the data table below to answer the following questions:

a. what do these isotopes have in common?
b. what is different about these isotopes?
c. **calculate the average atomic mass of this element and determine its identity.
d. **based on your answer above, complete the table below for isotope 2

isotope	nuclear symbol	isotope name
isotope	atomic mass (amu)	natural abundance
1	9.01	94.1%
2	10.04	4.55%
3	11.1	1.35%

Explanation:

Step1: Identify number of isotopes

The number of peaks in a mass - spectrum represents the number of isotopes. Without seeing the actual mass - spectrum data for element D, we can't give a specific number. But in general, count the peaks.

Step2: Determine isotope with greatest abundance

The tallest peak in a mass - spectrum represents the isotope with the greatest natural abundance.

Step3: Find isotope with most neutrons

The isotope with the highest mass number (highest - m/z value peak) usually has the greatest number of neutrons (since mass number = protons+neutrons and for isotopes of the same element, number of protons is constant).

Step4: Identify element D

To identify element D, we need to calculate the average atomic mass using the mass - spectrum data (isotope masses and their abundances) and compare it with known average atomic masses of elements.

Step5: Find atomic number

The atomic number of an element is unique and can be determined from the element's identity.

Step6: Calculate electrons in Au³⁺

A neutral Au (gold) atom has 79 electrons. An Au³⁺ ion has lost 3 electrons. So, the number of electrons is \(79 - 3=76\).

Step7: Identify the element

A neutral atom with 6 electrons has 6 protons (in a neutral atom, number of electrons = number of protons), so it is carbon.

Step8: Recall isotope property

All isotopes of a given element have the same atomic number.

Step9: Calculate electrons in Mg²⁺

A neutral Mg atom has 12 electrons. A Mg²⁺ ion has lost 2 electrons, so it has \(12 - 2 = 10\) electrons.

Step11: Compare K atom and K⁺ ion

A neutral K atom has one more electron than a K⁺ ion.

Step12a: Isotope commonality

Isotopes of the same element have the same atomic number.

Step12b: Isotope difference

Isotopes of the same element have different mass numbers (due to different numbers of neutrons).

Step12c: Calculate average atomic mass

The formula for average atomic mass \(A=\sum_{i = 1}^{n}m_i\times p_i\), where \(m_i\) is the mass of isotope \(i\) and \(p_i\) is the percentage abundance of isotope \(i\) (expressed as a decimal). For the given data:
\[A=(9.01\times0.941)+(10.04\times0.0455)+(11.1\times0.0135)\]
\[A = 9.01\times0.941+10.04\times0.0455 + 11.1\times0.0135=8.48841+0.45682+0.14985 = 9.09508\approx9.10\]
This is close to the average atomic mass of beryllium.

Step12d: Complete isotope table

For isotope 2 (assuming atomic number of the element is determined from step 12c as 4 for beryllium), the nuclear symbol is \(_{4}^{10}Be\) and the isotope name is beryllium - 10.

Answer:

1. Number of peaks in mass - spectrum of element D.
2. Tallest peak in mass - spectrum of element D.
3. Peak with highest m/z value in mass - spectrum of element D.
4. Element identity after calculating average atomic mass from mass - spectrum data.
5. Atomic number corresponding to element D identity.
6. a. 76
7. a. carbon
8. c. atomic number
9. a. 10
10. a. More electrons

12a. Same atomic number
12b. Different mass numbers
12c. Average atomic mass is approximately 9.10, element is beryllium
12d. Isotope: 2, Nuclear Symbol: \(_{4}^{10}Be\), Isotope Name: beryllium - 10