Question

(a) True or false: The hydrogen atom is most stable when it has a full octet of electrons. (b) How many electrons must a sulfur atom gain to achieve an octet in its valence shell? (c) If an atom has the electron configuration \(1 s^{2} 2 s^{2} 2 p^{3}\), how many electrons must it gain to achieve an octet?

Short answer

(a) False. Hydrogen is most stable with a duet of electrons, not an octet. (b) Sulfur must gain 2 electrons to achieve an octet in its valence shell. (c) The atom with electron configuration \(1s^2 2s^2 2p^3\) needs to gain 3 electrons to achieve an octet.

Step-by-step solution

(a) True or false: The hydrogen atom is most stable when it has a full octet of electrons.

The statement is false. A hydrogen atom has only one electron and forms a bond by sharing one electron with another atom. Since hydrogen only has one energy level (the 1s shell), it can hold a maximum of 2 electrons, and it doesn't need to have an octet of electrons to be stable. Hydrogen is most stable with a duet of electrons, which satisfies the 1s orbital.

(b) How many electrons must a sulfur atom gain to achieve an octet in its valence shell?

To know how many electrons a sulfur atom needs to gain to achieve an octet, we need to find its valence electron configuration. Sulfur (S) has an atomic number of 16, which means it has 16 electrons. The electron configuration of sulfur is \(1s^2 2s^2 2p^6 3s^2 3p^4\). The valence shell is the outermost shell with electrons, which in sulfur's case is the third shell, with six electrons in total (two in the 3s and four in the 3p orbitals). In order to achieve an octet, sulfur must gain 2 more electrons to fill its valence shell of 3p orbital.

(c) If an atom has the electron configuration \(1s^2 2s^2 2p^3\), how many electrons must it gain to achieve an octet?

The given electron configuration has an outermost shell of '2', containing a total of 5 electrons (2 in the 2s orbital, and 3 in the 2p orbital). To achieve an octet in its valence shell, it needs to have 8 electrons. So, the atom needs 3 more electrons in order to achieve an octet.

Key concepts

Octet Rule

The octet rule is a fundamental concept in chemistry that helps us understand the electron configurations of atoms. Essentially, this rule states that atoms are most stable when they have eight electrons in their valence shell. This configuration is similar to that of the noble gases, which are inherently stable. Atoms will often gain, lose, or share electrons to achieve this stable configuration.

• For example, the sulfur atom, which has six valence electrons, will gain two electrons to fulfill the octet rule, thus becoming more stable.
• This rule helps predict the types of ions or molecules that an atom will form in chemical reactions.

The octet rule is a simplified model, and while it is highly useful, not all elements strictly follow it. Exceptions exist, especially among transition metals and molecules with an odd number of electrons.

Valence Electrons

Valence electrons are the electrons present in the outermost shell of an atom. These electrons are crucial because they determine how an atom will interact chemically with other atoms. Understanding valence electrons is key to predicting how elements form bonds.

• For instance, in a sulfur atom, the valence electrons are found in the third energy level, specifically in the 3s and 3p orbitals.
• Sulfur has six valence electrons, so it tends to gain two more to reach the octet configuration, enabling it to form substances like sulfides.
• Valence electrons are responsible for the atomic properties including reactivity, bonding tendencies, and conductivity.

Knowing how to count valence electrons and determine their configuration helps understand an element's chemistry and how it bonds.

Atomic Stability

Atomic stability is a concept that is often associated with the energy levels and electron configurations of atoms. Atoms are considered stable when they have full valence shells. The pursuit of stability is a key motivator in chemical reactions.Atoms with incomplete outer shells are usually reactive as they seek to either gain, lose, or share electrons to achieve a more stable state.

• For example, in the electron configuration \(1s^2 2s^2 2p^3\), the atom has five valence electrons and requires three more to stabilize by completing the octet in its second shell.
• Hydrogen, on the other hand, achieves stability with just two electrons in its valence shell, because its most stable form "fills" the first, and only, energy level it has, known as the duet rule.

Reaching an electron configuration similar to the noble gases is often an indicator of atomic stability. This drives bonding processes, where electrons are transferred or shared to fulfill stable configurations.