We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is ` and sulfide is .

The only answer choices that could be right must have in them. We then need to see that barium usually has a charge of , as the periodic table shows us, and so we need a charge of to cancel that out. The answer is .

.. ..

:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs

.. | .. for a total of 9 pairs of unpaired electrons

:F:

..

We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is ` and sulfide is .

The only answer choices that could be right must have in them. We then need to see that barium usually has a charge of , as the periodic table shows us, and so we need a charge of to cancel that out. The answer is .

.. ..

:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs

.. | .. for a total of 9 pairs of unpaired electrons

:F:

..

We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is ` and sulfide is .

The only answer choices that could be right must have in them. We then need to see that barium usually has a charge of , as the periodic table shows us, and so we need a charge of to cancel that out. The answer is .

.. ..

:F — B — F: Boron can have a violated octet (6 e-) and each F has 3 lone pairs

.. | .. for a total of 9 pairs of unpaired electrons

:F:

..

Ionic chemical compounds are always named with the metal before the non-metal. The correct way to name sodium chloride would be , and not , because sodium is the metal and chloride is the non-metal.

All the other examples have the metal before the non-metal. The other answer choices correspond to potassium chloride, magnesium sulfate, hydrogen chloride (hydrochloric acid), and calcium fluoride.

is the correct configuration for a neutral sodium atom.

A neutral sodium atom contains eleven electrons, so you can eliminate and which contain twelve and ten electrons, respectively.

Next, can be eliminated because of the Aufbau principal, which states that electrons are placed into orbitals from the lowest to highest energy. In this answer choice, the (lower energy) orbital is not completely filled, containing only five out of the possible six possible electron that it can hold. This orbital must be filled completely before electrons can be placed in the (higher energy) orbital.

is incorrect because there are seven electrons in the orbital. This is impossible, as p orbitals hold a maximum of six electrons.

The atomic number of aluminum is 13, which means it has 13 protons. All atoms with 13 protons are called aluminum. The mass number of aluminum is 27 and is the sum of neutrons and protons. We simply subtract the number of protons from the mass number to get the number of neutrons. Normally there are an equal number of electrons and protons. But since this aluminum exists as an ion with a +3 charge, it has lost three electrons and has only 10 electrons.

is the correct configuration for a neutral sodium atom.

A neutral sodium atom contains eleven electrons, so you can eliminate and which contain twelve and ten electrons, respectively.

Next, can be eliminated because of the Aufbau principal, which states that electrons are placed into orbitals from the lowest to highest energy. In this answer choice, the (lower energy) orbital is not completely filled, containing only five out of the possible six possible electron that it can hold. This orbital must be filled completely before electrons can be placed in the (higher energy) orbital.

is incorrect because there are seven electrons in the orbital. This is impossible, as p orbitals hold a maximum of six electrons.