Question

q1 chemistry: u2l4 avg. atomic mass. pre - work part 1: average atomic mass. examine the data for unknown element z below. isotope # mass % abundance 1 14.003 99.632% 2 15.001 0.368%. 1. based on the data above, what whole number do you think the average atomic mass will be closest to? __________ 2. look at the periodic table - which element do you think element x is? a. carbon (c) b. nitrogen (n) c. oxygen (o) d. fluorine (f) 3. explain your response to q2. examine the data for unknown element r below. isotope # mass % abundance 1 31.97 94.93% 2 32.97 0.76% 3 33.97 4.29% 4 35.97 0.02%. 4. based on the data above, what whole number do you think the average atomic mass will be closest to? ________ 5. look at the periodic table - which element do you think element r is? a. phosphorus (p) b. sulfur (s) c. chlorine (cl) d. arsenic (as) 6. explain your response to q6. examine the table below. use the data table to answer questions 8 - 11. atom a atom b atom c atom d atom e protons 11 79 9 13 11 neutrons 13 100 8 14 14 electrons 11 77 11 14 13. 7. which atoms are isotopes? ________ 8. *which atom(s) are positively charged ions? ________ 9. which atom(s) are negatively charged ions? ________ 10. which atom(s) are neutral atoms? __________

Explanation:

Step1: Calculate average atomic mass for element Z

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 its percent - abundance (in decimal form). For element Z:
\[

$$\begin{align*} A_Z&=(14.003\times0.99632)+(15.001\times0.00368)\\ &=14.003\times0.99632 + 15.001\times0.00368\\ &=13.948+0.0552\\ &=14.0032\approx14 \end{align*}$$

\]

Step2: Identify element Z

Nitrogen (N) has an average atomic mass close to 14. The number of protons in an atom determines the element. Nitrogen has 7 protons, and its average atomic mass from the periodic table is approximately 14.01. So element Z is nitrogen.

Step3: Calculate average atomic mass for element R

\[

$$\begin{align*} A_R&=(31.97\times0.9493)+(32.97\times0.0076)+(33.97\times0.0429)+(35.97\times0.0002)\\ &=(31.97\times0.9493)+(32.97\times0.0076)+(33.97\times0.0429)+(35.97\times0.0002)\\ &=30.35+0.25+1.46+0.01\\ &=32.07\approx32 \end{align*}$$

\]

Step4: Identify element R

Sulfur (S) has an average atomic mass close to 32. From the periodic table, sulfur has an average atomic mass of approximately 32.06.

Step5: Determine isotopes

Isotopes are atoms of the same element with different numbers of neutrons. Atoms A and E have the same number of protons (11), so they are isotopes.

Step6: Determine charged ions

An atom is a positively - charged ion if the number of protons is greater than the number of electrons. Atom C has 9 protons and 11 electrons, so it is a negatively - charged ion. Atom B has 79 protons and 77 electrons, so it is a positively - charged ion.
An atom is a neutral atom if the number of protons is equal to the number of electrons. Atoms A and D are neutral atoms since the number of protons equals the number of electrons in each of them.

Answer:

1. 14
2. b. Nitrogen (N)
3. The average atomic mass is close to 14, and nitrogen has an average atomic mass of approximately 14.01 on the periodic table.
4. 32
5. b. Sulfur (S)
6. The average atomic mass is close to 32, and sulfur has an average atomic mass of approximately 32.06 on the periodic table.
7. Atoms A and E
8. Atom B
9. Atom C
10. Atoms A and D