Question

part d. isotopes.

1. complete the table below with the correct isotope data.

isotope name	# of p⁺	# of e⁻	# of n⁰	atomic number	mass number	isotope symbol

1. draw the bohr atomic model for oxygen - 17 using the model to the right.
2. what is the difference between lithium - 6 and lithium - 7?

how are the two isotopes alike?

1. which isotope has the most protons, carbon - 15, nitrogen - 15, or oxygen - 15? (circle your choice)

list the number of neutrons in each isotope.

1. why are electrons not included in the mass number?
2. an isotope has a mass number of 31 and contains 16 neutrons. give the isotope name.

create the isotope symbol.

1. if an isotope contains 9 protons and 9 electrons, can we obtain the mass number? explain why or why not.

part e. the periodic table.

1. what is the element symbol for the element nickel?

if an atom of nickel has 31 neutron what would be its isotope symbol?

1. list an element that is in the same group as gallium, $_{31}ga$.
2. vanadium, $_{23}v$, is in period 1 / 2 / 3 / 4 / 5 / 6 / 7. (circle your answer)
3. what is the average atomic mass of neon, ne? (include correct units)
4. what is the molar mass of beryllium, be? (include correct units)
5. what family does strontium, sr, belong to?
6. list all of the noble gases.
7. what is the atomic number of sulfur?
8. for an ion of oxygen - 18, list the protons and electrons.
9. how many protons, neutrons, and electrons are in $_{20}^{42}ca^{2 + }$

Explanation:

Step1: Recall isotope - atomic number relationship

The atomic number of an element is equal to the number of protons. For $\ce{^{14}_{6}C}$, the atomic number is 6, so the number of protons $p^{+}=6$. In a neutral atom, the number of electrons $e^{-}$ is equal to the number of protons, so $e^{-}=6$. The mass number is 14, and the number of neutrons $n^{0}=$ mass number - atomic number, so $n^{0}=14 - 6=8$.
| Isotope Name | # of $p^{+}$ | # of $e^{-}$ | # of $n^{0}$ | Atomic Number | Mass Number | Isotope Symbol |
| ---- | ---- | ---- | ---- | ---- | ---- | ---- |
| Carbon - 14 | 6 | 6 | 8 | 6 | 14 | $\ce{^{14}_{6}C}$ |

Step2: Draw Bohr model for oxygen - 17

Oxygen has an atomic number of 8. So, for oxygen - 17, the number of protons $p^{+}=8$, the number of electrons $e^{-}=8$ (in a neutral atom), and the number of neutrons $n^{0}=17 - 8 = 9$. In the Bohr model, the first shell can hold 2 electrons and the second shell can hold 6 electrons for oxygen. Draw a nucleus with 8 protons and 9 neutrons, and two electron - shells with 2 and 6 electrons respectively.

Step3: Compare lithium - 6 and lithium - 7

Lithium has an atomic number of 3. For lithium - 6, $p^{+}=3$, $e^{-}=3$, $n^{0}=6 - 3=3$. For lithium - 7, $p^{+}=3$, $e^{-}=3$, $n^{0}=7 - 3 = 4$. The difference is the number of neutrons (lithium - 7 has one more neutron than lithium - 6). They are alike in that they have the same number of protons and electrons (same atomic number, same element).

Step4: Determine number of protons and neutrons in isotopes

Carbon has an atomic number of 6, nitrogen has an atomic number of 7, and oxygen has an atomic number of 8. So, oxygen - 15 has the most protons. For carbon - 15, $n^{0}=15 - 6 = 9$; for nitrogen - 15, $n^{0}=15 - 7 = 8$; for oxygen - 15, $n^{0}=15 - 8 = 7$.

Step5: Explain electron - mass number exclusion

Electrons have a very small mass compared to protons and neutrons. The mass of an electron is approximately $\frac{1}{1836}$ of the mass of a proton. So, electrons are not included in the mass number which is the sum of protons and neutrons.

Step6: Identify isotope from mass and neutron number

If the mass number is 31 and the number of neutrons is 16, then the number of protons $p^{+}=31 - 16=15$. The element with atomic number 15 is phosphorus. The isotope name is phosphorus - 31, and the isotope symbol is $\ce{^{31}_{15}P}$.

Step7: Determine mass number from proton number

If an isotope has 9 protons, the element is fluorine. But we cannot obtain the mass number just from the number of protons and electrons. We need to know the number of neutrons as well, since mass number = number of protons+number of neutrons.

Step8: Find nickel element and isotope symbol

The element symbol for nickel is $\ce{Ni}$. Nickel has an atomic number of 28. If it has 31 neutrons, the mass number is $28 + 31=59$. The isotope symbol is $\ce{^{59}_{28}Ni}$.

Step9: Find element in same group as gallium

Elements in the same group have the same number of valence electrons. Gallium is in group 13. An element in the same group is aluminum ($\ce{Al}$).

Step10: Locate vanadium in periodic table

Vanadium has an atomic number of 23. It is in period 4.

Step11: Find average atomic mass of neon

The average atomic mass of neon is approximately 20.18 amu.

Step12: Find molar mass of beryllium

Beryllium has an atomic mass of approximately 9.012 g/mol.

Step13: Identify strontium's family

Strontium is in group 2, and it belongs to the alkaline - earth metals family.

Step14: List noble gases

The noble gases are helium ($\ce{He}$), neon ($\ce{Ne}$), argon ($\ce{Ar}$), krypton ($\ce{Kr}$), xenon ($\ce{Xe}$), and radon ($\ce{Rn}$).

Step15: Find atomic number of sulfur

The atomic number of sulfur is 16.

Step16: Determine protons and electrons in oxygen - 18 ion

Oxygen has an atomic number of 8. For an oxygen - 18 ion, if it is a simple ion, it usually forms a 2 - ion ($O^{2 - }$). The number of protons is 8, and the number of electrons is 10.

Step17: Determine sub - atomic particles in $\ce{^{42}_{20}Ca^{2+}}$

The atomic number of calcium is 20, so the number of protons $p^{+}=20$. The mass number is 42, so the number of neutrons $n^{0}=42 - 20=22$. Since it is a $2+$ ion, the number of electrons $e^{-}=20 - 2 = 18$.

Answer:

1. See table above.
2. Draw a nucleus with 8 protons and 9 neutrons, and two electron - shells with 2 and 6 electrons respectively.
3. Difference: number of neutrons (lithium - 7 has one more neutron). Alike: same number of protons and electrons.
4. Oxygen - 15; Carbon - 15: 9 neutrons, Nitrogen - 15: 8 neutrons, Oxygen - 15: 7 neutrons.
5. Electrons have very small mass compared to protons and neutrons.
6. Phosphorus - 31; $\ce{^{31}_{15}P}$
7. No, we need to know the number of neutrons.
8. $\ce{Ni}$; $\ce{^{59}_{28}Ni}$
9. $\ce{Al}$
10. 4
11. 20.18 amu
12. 9.012 g/mol
13. Alkaline - earth metals
14. $\ce{He}$, $\ce{Ne}$, $\ce{Ar}$, $\ce{Kr}$, $\ce{Xe}$, $\ce{Rn}$
15. 16
16. Protons: 8, Electrons: 10 (assuming $O^{2 - }$)
17. Protons: 20, Neutrons: 22, Electrons: 18