Question

practice: isotope calculations #2

1. complete the following table.

nuclear notation, atom or ion?, atomic #, mass #, # of protons, # of neutrons, # of electrons
, , , 24, 11, , 11
³²s⁻², ion, 16, 32, 16, ,
, , 6, 14, , , 6
²⁴mg, atom, , , , ,
, , 64, , 34, 28,
²⁰⁷pb, atom, , , , ,
, , 53, 127, , , 53
²³⁸u, atom, , , , ,
, , , 20, 21, 20,
, , 20, 40, , , 18

1. explain the difference between mass number and average atomic mass.
2. which tells you the most common version of an element?
3. place a star next to each column that represents an isotope that is the most common for that element.
4. explain the difference between an atom and an ion.

the atom unit

Explanation:

Step1: Recall atomic - related concepts

Atomic number = number of protons. Mass number = number of protons + number of neutrons. For a neutral atom, number of electrons = number of protons. For an ion, adjust the number of electrons according to the charge.

Step2: Fill the first row

Atomic number = 11 (given number of protons). Mass number = 24. Number of neutrons = Mass number - Number of protons = 24 - 11=13. Since number of electrons = 11, it is a neutral atom. Nuclear notation: $^{24}_{11}X$ (where X is the element with atomic number 11, which is Na).

Step3: Fill the second row (for $^{32}S^{2 -}$)

Number of neutrons = Mass number - Number of protons = 32 - 16 = 16. Since it is a $2 -$ ion, number of electrons = 16+2 = 18.

Step4: Fill the third row

Atomic number = 6 (given number of protons). Mass number = 14. Number of neutrons = 14 - 6 = 8. Since number of electrons = 6, it is a neutral atom. Nuclear notation: $^{14}_{6}C$.

Step5: Fill the fourth row (for $^{24}Mg$)

Atomic number of Mg is 12. Number of neutrons = Mass number - Number of protons = 24 - 12 = 12. For a neutral atom, number of electrons = 12.

Step6: Fill the fifth row

Atomic number = 30 (since number of electrons in a neutral atom = number of protons, and here number of electrons = 28 for a $2+$ ion, so number of protons = 30). Mass number = 64. Number of neutrons = 64 - 30 = 34. Nuclear notation: $^{64}_{30}Zn^{2+}$.

Step7: Fill the sixth row (for $^{207}Pb$)

Atomic number of Pb is 82. Number of neutrons = Mass number - Number of protons = 207 - 82 = 125. For a neutral atom, number of electrons = 82.

Step8: Fill the seventh row (for $^{127}I$)

Atomic number = 53. Number of neutrons = Mass number - Number of protons = 127 - 53 = 74. For a neutral atom, number of electrons = 53. Nuclear notation: $^{127}_{53}I$.

Step9: Fill the eighth row (for $^{238}U$)

Atomic number of U is 92. Number of neutrons = Mass number - Number of protons = 238 - 92 = 146. For a neutral atom, number of electrons = 92.

Step10: Fill the ninth row

Atomic number = 20. Mass number = 41. Number of neutrons = 41 - 20 = 21. For a neutral atom, number of electrons = 20. Nuclear notation: $^{41}_{20}Ca$.

Step11: Fill the tenth row

Atomic number = 20. Number of neutrons = Mass number - Number of protons = 40 - 20 = 20. Since number of electrons = 18, it is a $2+$ ion. Nuclear notation: $^{40}_{20}Ca^{2+}$.

2. **Answer for question 2**:
Mass number is the sum of the number of protons and neutrons in the nucleus of a single isotope of an element. Average atomic mass is the weighted - average of the masses of all naturally - occurring isotopes of an element, taking into account their relative abundances.
3. **Answer for question 3**:
The most common version of an element is often indicated by the isotope with the highest natural abundance. This is related to the average atomic mass value on the periodic table, as the average atomic mass is weighted towards the most abundant isotope.
4. **Answer for question 4**:
This requires knowledge of the natural abundances of isotopes of each element. For example, for Mg, $^{24}Mg$ is a common isotope; for S, $^{32}S$ is common; for C, $^{12}C$ is the most common (not in the table but for reference); for Pb, $^{208}Pb$ is a common one (not in the table), etc. Without specific abundance data for all the isotopes in the table, it's hard to precisely mark all. But generally, for the given isotopes like $^{32}S$ and $^{24}Mg$, they are relatively common isotopes of their respective elements.
5. **Answer for question 5**:
An atom is a neutral particle where the number of protons equals the number of electrons. An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net positive or negative charge. A positive ion (cation) has lost electrons, and a negative ion (anion) has gained electrons.

Answer:

Nuclear Notation	Atom or Ion?	Atomic #	Mass #	# of Protons	# of Neutrons	# of Electrons
$^{32}_{16}S^{2 -}$	Ion	16	32	16	16	18
$^{14}_{6}C$	Atom	6	14	6	8	6
$^{24}_{12}Mg$	Atom	12	24	12	12	12
$^{64}_{30}Zn^{2+}$	Ion	30	64	30	34	28
$^{207}_{82}Pb$	Atom	82	207	82	125	82
$^{127}_{53}I$	Atom	53	127	53	74	53
$^{238}_{92}U$	Atom	92	238	92	146	92
$^{41}_{20}Ca$	Atom	20	41	20	21	20
$^{40}_{20}Ca^{2+}$	Ion	20	40	20	20	18

1. Mass number is for a single isotope, average atomic mass is weighted - average of all isotopes.
2. The isotope with the highest natural abundance.
3. Varies by element, e.g., $^{32}S$ and $^{24}Mg$ are relatively common isotopes of S and Mg respectively.
4. An atom is neutral, an ion has a charge due to gain or loss of electrons.