Understanding the Octet Rule

Atoms tend to be stable when they achieve a complete outer electron shell. The octet rule explains how atoms gain, lose, or share electrons to mimic the electron configuration of noble gases. Based on this rule, which of the following best describes the octet rule?

• Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outermost shell.

• Atoms are stable when they have the same number of protons and neutrons.

• Elements are arranged on the periodic table in groups of eight.

• Atoms form chemical bonds to increase their atomic number to eight.

Elements in Group 2 of the periodic table, also known as alkaline earth metals, have two electrons in their outermost shell. To achieve stability, these elements often lose their valence electrons during chemical reactions. Which statement best describes elements in Group 2 concerning the octet rule?

• They tend to gain six electrons to complete their octet.

• They lose two electrons to form a stable outer shell.

• They share two electrons to form covalent bonds.

• They neither gain nor lose electrons.

Group 1 elements, like sodium (Na), have only one electron in their outer shell, making them highly reactive. These elements tend to lose this electron to achieve a stable electron configuration. Which element is most likely to lose one electron to satisfy the octet rule?

• Chlorine (Cl)

• Sodium (Na)

• Carbon (C)

• Neon (Ne)

Oxygen, sulfur, and other Group 16 elements have six valence electrons in their outermost shell. These elements achieve stability by either sharing or gaining electrons to fulfill the octet rule. Which of these elements will likely gain two electrons to achieve a stable octet?

• Magnesium (Mg)

• Oxygen (O)

• Fluorine (F)

• Aluminum (Al)

Group 17 elements, also called halogens, are highly reactive non-metals found in the periodic table. They have seven valence electrons and require only one more electron to complete their octet. What makes Group 17 elements highly reactive?

• They have seven valence electrons and need only one to complete their octet.

• They lack protons in their nucleus.

• Their outer shell is already full.

• They are found in diatomic forms in nature.

When calcium (Ca), an element in Group 2, reacts with chlorine (Cl), a halogen in Group 17, they form calcium chloride (CaCl₂). This chemical bond is a result of calcium transferring electrons to chlorine. What happens during this reaction?

• Calcium shares electrons with chlorine atoms.

• Calcium gains two electrons to form a stable octet.

• Calcium loses two electrons, and each chlorine atom gains one electron.

• Calcium and chlorine form a molecule by sharing electrons equally.

Elements on the periodic table can gain or lose electrons depending on their group number. For example, elements in Group 15 need three electrons to fill their outer shell, while Group 1 elements lose one. Which of the following elements is most likely to gain three electrons to achieve a full octet?

• Phosphorus (P)

• Sodium (Na)

• Magnesium (Mg)

• Neon (Ne)

Chemical reactions often occur between elements that complement each other’s need to achieve a stable octet. For example, Group 1 elements tend to lose electrons, while Group 17 elements tend to gain electrons. Which of the following pairs of elements would most likely form an ionic bond to satisfy the octet rule?

• Potassium (K) and Chlorine (Cl)

• Carbon (C) and Oxygen (O)

• Neon (Ne) and Sodium (Na)

• Magnesium (Mg) and Hydrogen (H)

Oxygen belongs to Group 16 and has six valence electrons. When oxygen reacts chemically, it often gains electrons. How many electrons must oxygen gain to achieve a full octet?

• 1

• 2

• 6

• 8

Neon (Ne) belongs to the noble gases in Group 18, which are known for their stability. Why are noble gases generally unreactive?

• They have a full outer shell of electrons.

• They lack protons in their nucleus.

• They are the smallest atoms in their period.

• They have an uneven number of neutrons.