Answer:
1) Ca: [Ar]4s²
2) Pm: [Xe]6s²4f⁵
Explanation:
1) Ca:
Its atomic number is 20. So it has 20 protons and 20 electrons.
Since it is in the row (period) 4 the noble gas before it is Ar, and the electron configuration is that of Argon whose atomic number is 18.
So, you have two more electrons (20 - 18 = 2) to distribute.
Those two electrons go the the orbital 4s.
Finally, the electron configuration is [Ar] 4s².
2) Pm
The atomic number of Pm is 61, so it has 61 protons and 61 electrons.
Pm is in the row (period) 6. So, the noble gas before Pm is Xe.
The atomic number of Xe is 54.
Therefore, you have to distribute 61 - 54 = 7 electrons on the orbitals 6s and 4f.
The resultant distribution for Pm is: [Xe]6s² 4f⁵.
Answer:
Rank in increasing order of effective nuclear charge:
Explanation:
This explains the meaning of effective nuclear charge, Zeff, how to determine it, and the calculations for a valence electron of each of the five given elements: F, Li, Be, B, and N.
<u>1) Effective nuclear charge definitions</u>
- While the total positive charge of the atom nucleus (Z) is equal to the number of protons, the electrons farther away from the nucleus experience an effective nuclear charge (Zeff) less than the total nuclear charge, due to the fact that electrons in between the nucleus and the outer electrons partially cancel the atraction from the nucleus.
- Such effect on on a valence electron is estimated as the atomic number less the number of electrons closer to the nucleus than the electron whose effective nuclear charge is being determined: Zeff = Z - S.
<u><em>2) Z eff for a F valence electron:</em></u>
- F's atomic number: Z = 9
- Total number of electrons: 9 (same numer of protons)
- Period: 17 (search in the periodic table or do the electron configuration)
- Number of valence electrons: 7 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 9 - 7 = 2
- Zeff = Z - S = 9 - 2 = 7
<u><em>3) Z eff for a Li valence eletron:</em></u>
- Li's atomic number: Z = 3
- Total number of electrons: 3 (same number of protons)
- Period: 1 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 1 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 3 - 1 = 2
- Z eff = Z - S = 3 - 2 = 1.
<em>4) Z eff for a Be valence eletron:</em>
- Be's atomic number: Z = 4
- Total number of electrons: 4 (same number of protons)
- Period: 2 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 2 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 4 - 2 = 2
- Z eff = Z - S = 4 - 2 = 2
<u><em>5) Z eff for a B valence eletron:</em></u>
- B's atomic number: Z = 5
- Total number of electrons: 5 (same number of protons)
- Period: 13 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 3 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 5 - 3 = 2
- Z eff = Z - S = 5 - 2 = 3
<u><em>6) Z eff for a N valence eletron:</em></u>
- N's atomic number: Z = 7
- Total number of electrons: 7 (same number of protons)
- Period: 15 (search on the periodic table or do the electron configuration)
- Number of valence electrons: 5 (equal to the last digit of the period's number)
- Number of electrons closer to the nucleus than a valence electron: S = 7 - 5 = 2
- Z eff = Z - S = 7 - 2 = 5
<u><em>7) Summary (order):</em></u>
Atom Zeff for a valence electron
- <u>Conclusion</u>: the order is Li < Be < B < N < F
Grams of oxygen are required to react with 13.0 grams of octane (C8H18) in the combustion of octane in gasoline is 45.5g
Octane is a hydrocarbon which burns in gasoline in presence of oxygen according to the given balanced chemical equation,
2C₈H₁₈ + 25O₂------> 16CO₂ + 18H₂0
Molar mass of octane = 114.23g/mol
Molar mass of Oxygen = 32g/mol
According to the stiochiometry of the balanced equation the mole ratio of Octane and Oxygen is 2:25
2 mole of octane needs 25 mole of oxygen
1 mole of octane needs 12.5 moleof oxygen
114.23g of octane needs 400g of oxygen
13g of octane needs 45.5g of oxygen
Mass of oxygen needed =45.5g
Hence, the Mass of oxygen needed is 45.5g for the combustion of octane in gasoline.
Learn more about Octane here, brainly.com/question/21268869
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<h3>
Answer:</h3>
0.75 moles NaOH
<h3>
Explanation:</h3>
We are given;
Volume of NaOH solution = 2.5 Liters
Molarity of NaOH = 0.300 M
We are required to calculate the moles of NaOH
We need to establish the relationship between moles, molarity and volume of a solution.
That would be;
Concentration/molarity = Moles ÷ Volume
Therefore;
Moles = Concentration × Volume
Thus;
Moles of NaOH = 0.300 moles × 2.50 L
= 0.75 moles
Therefore, the number of moles of NaOH is 0.75 moles
Molecular Motion<span> is the speed at which molecules or atoms move dependent on temperature and state of matter.
Explanation:
</span>All molecules are<span> in constant motion. Molecules of a liquid have </span>a lot of<span> freedom of movement than those </span>in an exceedingly<span> solid. Molecules </span>in an exceedingly<span> gas have </span>the best<span> degree of motion.</span>
<span>
Heat, temperature </span>and also the<span> motion of molecules </span>area unit<span> all </span>connected<span>. Temperature </span>could be a life<span> of </span>the common K.E.<span> of the molecules </span>in an exceedingly<span> material. Heat </span>is that the<span> energy transferred between materials that have </span>completely different temperatures<span>. Increasing the temperature </span>will increase<span> the </span>travel<span> motion of molecules Energy </span>is expounded<span> to temperature by the relationship.</span>
