Question

1 chemistry: u2l11 electron configu-
b. *electrons will occupy a p - orbital only after
i. the previous s - orbital is half full
ii. the previous s - orbital is completely full
iii. the previous s - orbital is empty
c. *electrons can begin to occupy energy levels with the next highest integer designation (e.g. 2 vs. 1, 3 vs. 2) only after on the energy level below it are occupied.
i. half of the orbitals
ii. at least one of the orbitals
iii. all of the orbitals

1. the pauli exclusion principle describes the restriction on the placement of electrons into the same orbital. the pauli exclusion principle can be expressed as: \if two electrons occupy the same orbital, they must have .\ circle the correct answer:

the same spin opposite spins

1. hund’s rule describes how electrons are distributed among orbitals of the same sublevel when there is more than one way to distribute them. hund’s rule consists of two important ideas.

a. electrons will pair up in an orbital only when
i. there is an even number of electrons in the sublevel
ii. all orbitals in the same sublevel have one electron
b. when single electrons occupy different orbitals of the same sublevel,
i. they all have the same spin
ii. they all have different spins
iii. their spins are random
additional review

1. **the mass number of an individual atom is determined by adding:
2. **on the elemental symbol below, draw an arrow and label the atomic mass, atomic number, and charge:

$_{7}^{15}n^{3 - }$

1. *the nitrogen ion above has protons, neutrons, and electrons.
2. why is this a nitrogen ion and not a nitrogen atom?

Explanation:

• b: Electrons fill orbitals in order of increasing energy. The s - orbital has lower energy than the p - orbital and must be completely full before electrons enter the p - orbital.
• c: Electrons fill lower - energy levels completely before moving to higher energy levels.
• 9: According to the Pauli exclusion principle, two electrons in the same orbital must have opposite spins.
• 10a: Hund's rule states electrons will pair up in an orbital only when all orbitals in the same sublevel have one electron.
• 10b: When single electrons occupy different orbitals of the same sublevel, they all have the same spin to minimize electron - electron repulsion.
• 11: The mass number of an atom is the sum of protons and neutrons.
• 13: For the ion $^{15}_{7}N^{3 - }$, the atomic number (number of protons) is 7. The mass number is 15, so the number of neutrons is $15 - 7=8$. The ion has a 3 - charge, so the number of electrons is $7 + 3=10$.
• 14: It is an ion and not an atom because it has a non - zero charge. An atom is neutral with equal numbers of protons and electrons, while this species has 3 more electrons than protons, giving it a 3 - charge.

Answer:

• b. ii. the previous s - orbital is completely full
• c. iii. all of the orbitals
• 9. opposite spins
• 10a. ii. All orbitals in the same sublevel have one electron
• 10b. i. They all have the same spin
• 11. Protons and neutrons
• 13. 7 protons, 8 neutrons, 10 electrons
• 14. It has a non - zero charge (3 - charge), while a nitrogen atom is neutral.