Atoms and Elements - Physical Chemistry

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 ml are the same. However, ms 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 charge on the ion is equal to the difference between the number of protons and electrons:

The element has 13 protons, which means its atomic number is also 13. Thus this element is aluminum.

The charge on the ion is equal to the difference between the number of protons and electrons.

The element has 35 protons, thus its atomic number is 35, which corresponds to bromine.

Aufbau's Principle says that electrons fill lower energy levels first. Hund's Rule dictates that electrons fill singly if possible.

Although it may seem counterintuitive, atomic radius does decrease from left to right on the periodic table. The reason for this is because the added positive charge in the nucleus causes the elctrons to be pulled more strongly towards the center, which decreases the atomic radius.

Electronegativity values become greater as you move up and to the right on the periodic table. Of the four atoms listed, sulfur is the highest up and farthest to the right, giving it the greatest electronegativity.

Electron affinity is the energy released when an atom gains an electron. The amount of energy released is higher if the atom readily accepts the electron and has high affinity, or ‘attraction’, for the electron. As we go towards the right on the periodic table, elements like to gain electrons to complete their octet; therefore, electron affinity increases as we go towards the right. As we go down, electron affinity decreases because of increases in atomic size. This means that the electron affinity increases as we go top-right. The only other listed periodic trend that increases as we go top-right is electronegativity.

Note that number of valence electrons and polarity are generally not considered periodic trends.

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 1s22s22p63s 2 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.

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.

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.

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.

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.

To answer this question, we need to find the electron configuration of both elemental sodium and sodium cation. If we look at the periodic table we can see that sodium is found on the first column. Since it is found in the first column, sodium has one valence electron. To complete octet, sodium will readily lose an electron and become a positively charged sodium ion. The electron configuration for sodium is . The electron configuration for sodium ion is (because it lost its electron in the orbital). This means that elemental sodium has an unpaired electron in its orbital; the sodium ion has no unpaired electrons. Recall that an unpaired electron can generate its own magnetic field and is called paramagnetic; therefore, solid sodium is paramagnetic. The number of electrons in the orbitals for both sodium and sodium ion is the same (6 electrons total in the orbital). The outermost shell of sodium is the third shell (because sodium is located on the third row of periodic table). Elemental sodium contains one electron in the orbital in the outermost shell whereas the sodium ion contains 6 electrons in its outermost shell.

Hybridization is a process involving the fusion, or hybridization, of and orbitals to form a unique orbital. It is possible for various combinations of and hybridization. Recall that there is one orbital and three orbitals in each shell. This means that the one orbital can hybridize with 1, 2, or all 3 orbitals. Since there are three total combinations, there are three types of hybridized orbitals. These are , , and . orbital has one and one orbital hybridized. This means that the orbital and the first orbital become a new orbital. A molecule with hybridization will have two orbitals and two orbitals. Similarly, an orbital is made from the hybridization of one and two orbitals. In hybridization, there are three orbitals and one orbital. Finally, an orbital has one and all three orbitals; therefore, an hybridized molecule will have four orbitals and no orbitals. The question states that there are three hybridized orbitals in this molecule; therefore, this molecule must be hybridized. The single orbital is unhybridized because the molecule probably has a double bond. Electrons in bonds in double and triple bonds cannot be found in hybridized orbitals; therefore, they need their own orbital. If a molecule has one bond (double bond), then it will need one orbital and will be hybridized (because this will give three hybridized orbitals and one orbital). If it has two bonds (triple bond), then it will need two orbitals and will be hybridized. If a molecule has all bonds (single bonds), then the molecule will require no empty orbitals for the delocalized electrons, and will be hybridized.

Carbon tetrachloride, , has a central carbon atom attached to four chlorine atoms. The bonds between the carbon atom and chlorine atoms are single covalent bonds. The electrons in a single bond ( bond) can be found in hybridized orbitals. Since carbon tetrachloride only has single bonds, the carbon atom can hybridize all of its orbitals (one and three ) in the outermost shell and form a hybridization; therefore, three orbitals and one orbital participate in hybridization leading us to the correct answer. Carbon dioxide, , has a central carbon atom bonded to two oxygen atoms. To complete octet, carbon and oxygen atoms have double bonds. This means that carbon dioxide has two bonds (two double bonds). Recall that electrons in bonds cannot reside in hybridized orbitals; therefore, to accommodate the two bonds we need two empty, unhybridized orbitals. This means that carbon dioxide will have hybridization of one and one orbital, giving it an hybridization.

Alkaline earth metals are group II elements; among them, radium has the largest atomic number.