Question

1. what is the mass number for a neon atom with 15 neutrons? what would the atoms full name be?
2. what is the mass for copper - 75?
3. how do you calculate average atomic mass?
4. the element copper has naturally occurring isotopes with mass numbers 63 and 65. the masses are: 62.93 amu (69.2%) and 64.93 (30.8%). calculate the average atomic mass of copper. show all your work. use proper number of sig - figs throughout your work.
5. rubidium is a soft, silvery - white metal that has two common isotopes, ^85rb and ^87rb. if the abundance of ^85rb is 72.2% and the abundance of ^87rb is 27.8%, what is the average atomic mass of rubidium?
6. uranium is used in nuclear reactors and is a rare element on earth. uranium has three common isotopes. if the abundance of ^234u is 0.01%, the abundance of ^235u is 0.71%, and the abundance of ^238u is 99.28%, what is the average atomic mass of uranium?
7. titanium has five common isotopes: ^46ti (8.0%), ^47ti (7.8%), ^48ti (73.4%), ^49ti (5.5%), ^50ti (5.3%). what is the average atomic mass of titanium?
8. why is the mass in amu of a carbon - 12 atom reported as 12.011 in the periodic table of the elements?
9. naturally occurring chlorine that is put in pools is 75.53 percent ^35cl (mass = 34.969 amu) and 24.47 percent ^37cl (mass = 36.966 amu). calculate the average atomic mass.
10. copper used in electric wires comes in two flavors (isotopes): ^63cu and ^65cu

Explanation:

Step1: Recall mass - number formula

The mass number ($A$) of an atom is the sum of the number of protons and neutrons. Neon has an atomic number ($Z$) of 10 (number of protons). Given 15 neutrons, $A=Z + N$. So $A = 10+15=25$. The full name is neon - 25.

Step2: Copper - 75 mass

Copper - 75 has a mass number of 75. In atomic mass units (amu), the mass is approximately 75 amu.

Step3: Average atomic mass formula

The average atomic mass ($\bar{M}$) of an element with isotopes is calculated as $\bar{M}=\sum_{i = 1}^{n}M_i\times\%_{i}$, where $M_i$ is the mass of the $i$ - th isotope and $\%_{i}$ is the percentage abundance of the $i$ - th isotope (expressed as a decimal).

Step4: Calculate copper average atomic mass

For copper:
$M_1 = 62.93$ amu, $\%_1=0.692$, $M_2 = 64.93$ amu, $\%_2 = 0.308$
$\bar{M}=(62.93\times0.692)+(64.93\times0.308)$
$=43.54756+19.99844$
$=63.546\approx63.55$ amu

Step5: Calculate rubidium average atomic mass

For rubidium:
$M_1$ (for $^{85}$Rb) $\approx85$ amu, $\%_1 = 0.722$, $M_2$ (for $^{87}$Rb) $\approx87$ amu, $\%_2=0.278$
$\bar{M}=(85\times0.722)+(87\times0.278)$
$=61.37+24.186$
$=85.556\approx85.56$ amu

Step6: Calculate uranium average atomic mass

For uranium:
$M_1$ (for $^{234}$U) $\approx234$ amu, $\%_1 = 0.0001$, $M_2$ (for $^{235}$U) $\approx235$ amu, $\%_2=0.0071$, $M_3$ (for $^{238}$U) $\approx238$ amu, $\%_3 = 0.9928$
$\bar{M}=(234\times0.0001)+(235\times0.0071)+(238\times0.9928)$
$=0.0234 + 1.6685+236.2864$
$=237.9783\approx238.0$ amu

Step7: Calculate titanium average atomic mass

For titanium:
$M_1$ (for $^{46}$Ti) $\approx46$ amu, $\%_1 = 0.080$, $M_2$ (for $^{47}$Ti) $\approx47$ amu, $\%_2=0.078$, $M_3$ (for $^{48}$Ti) $\approx48$ amu, $\%_3 = 0.734$, $M_4$ (for $^{49}$Ti) $\approx49$ amu, $\%_4=0.055$, $M_5$ (for $^{50}$Ti) $\approx50$ amu, $\%_5 = 0.053$
$\bar{M}=(46\times0.080)+(47\times0.078)+(48\times0.734)+(49\times0.055)+(50\times0.053)$
$=3.68+3.666+35.232+2.695+2.65$
$=47.923\approx47.92$ amu

Step8: Carbon - 12 mass in periodic table

The mass of carbon - 12 reported as 12.011 amu in the periodic table is because the periodic - table value is the average atomic mass of carbon, which takes into account the presence of other carbon isotopes (such as carbon - 13) in nature.

Step9: Calculate chlorine average atomic mass

For chlorine:
$M_1 = 34.969$ amu, $\%_1=0.7553$, $M_2 = 36.966$ amu, $\%_2 = 0.2447$
$\bar{M}=(34.969\times0.7553)+(36.966\times0.2447)$
$=26.4321857+9.0456702$
$=35.4778559\approx35.48$ amu

Step10: Copper isotopes in wires

This part seems to be an introduction without a specific question. If the question is about average atomic mass (similar to previous copper cases), we would use the formula $\bar{M}=\sum_{i = 1}^{n}M_i\times\%_{i}$ with appropriate abundances of $^{63}$Cu and $^{65}$Cu.

Answer:

1. Mass number: 25, Full name: neon - 25
2. Approximately 75 amu
3. $\bar{M}=\sum_{i = 1}^{n}M_i\times\%_{i}$
4. 63.55 amu
5. 85.56 amu
6. 238.0 amu
7. 47.92 amu
8. Due to presence of other carbon isotopes
9. 35.48 amu
10. No specific question answered. If about average atomic mass, use $\bar{M}=\sum_{i = 1}^{n}M_i\times\%_{i}$