From the periodic table, we find that the atomic number, i.e., the number of protons in the nucleus of  is 15. Given that the mass number is 32, and recalling the formula which relates mass number to the number of neutrons and protons: , we find that the number of neutrons in the nucleus of one atom of  is 17.

Transition metals extend from groups 3 through 12 and periods 4 through 7. Ru, in its neutral state, has 44 electrons. Therefore, when it becomes a  cation, it will have 42 electrons. 

The atomic number is equal to the number of protons in the element, so from the periodic table, we find that the element with atomic number 34 is selenium. Since , we calculate that the mass number is 70. Lastly, there are two more electrons than protons, so the charge will be .

Covalent bonds are by far the strongest, requiring  to be broken. 

Next are hydrogen bonds, which require between  to be broken.

Next are dipole-dipole interactions, which require  to be broken.

Finally, van der Waals forces are the weakest of those listed, requiring  to be broken.

An atom is considered to be in an excited state when one of the electrons has jumped to a higher energy level while a lower energy level is available. In the case of , an electron has jumped to the 2p energy level while there is still room in the lower 2s subshell. As a result, it is considered to be in an excited state.

Magnesium has an atomic number of 12, so the total number of electrons in its configuration should add up to twelve. The maximum number of electrons in the s subshell is two. Of all the answer choices, only 1s²2s²2p⁶3s² fits the criteria. The sum of the exponent values is 12, matching the atomic number of magnesium, and the number of electrons in the s and p subshells matches the maximum amount possible. 

Iron has an atomic number of 26, so the total number of electrons in its configuration should add up to twenty six. The maximum number of electrons in the s subshell is two. The sum of the exponent values is 26, matching the atomic number of magnesium, and the number of electrons in the s and p subshells matches the maximum amount possible. 

The Pauli Exclusion Principle explains various phenomena such as the structure of atoms and how different atoms combine to share electrons. When you have two electrons that are located in the same orbital, the quantum numbers n, l and m_l are the same. However, m_s will be different. Two electrons cannot have the same four electronic quantum numbers because no more than two electrons may occupy an orbital, and if they do, the spin of one must cancel the spin of the other so their spins will have a zero net spin angular momentum.

The hybridization of an atom can be determined by the number of atoms it is bonded to, as well as the number of lone pairs it has. Two of these variables would be sp, three variables would be sp², and four would be sp³.

The nitrogen in ammonia is bonded to three atoms of hydrogen, but also has a lone pair in order to satisfy its octet. This means that nitrogen exhibits sp³ hybridization.

Orbitals are regions in an electron shell where electrons might be located. There are several types of orbitals such as , and . Most elements found on the periodic table contain electrons within one of these orbitals. A characteristic of an orbital is that it can only contain two electrons maximum. A shell might contain multiple orbitals; however, each orbital can only contain two electrons. Each orbital has a unique shape that corresponds to the electron density (the possible location of an electron at a given point in time). The  orbital has a spherical shape whereas the  orbital has a dumbbell shape. As mentioned, a shell can contain multiple types of orbitals. A shell can typically contain one  orbital, three  orbitals, five  orbitals, and seven  orbitals. Remember that the shape of the orbital has no bearing on the amount of orbitals in a shell. An orbital is higher in energy if it is found farther away from the nucleus. The orbitals in order of increasing energy is as follows . Therefore, an  orbital has lower energy than a  orbital in the same shell.