Question

Describe what happens to the electron configurations of lithium and nitrogen when they react to form the lithium nitride.

Short answer

In the formation of lithium nitride, each lithium atom loses one electron becoming Li⁺ with configuration 1s², while nitrogen gains three electrons becoming N³⁻ with configuration 1s² 2s² 2p⁶.

Step-by-step solution

Identify Electron Configuration of Lithium

Lithium (Li) has an atomic number of 3, which means it has 3 protons and, when neutral, 3 electrons. The electron configuration of Li is 1s² 2s¹. In its ground state, lithium has 2 electrons in the first energy level (1s orbital) and 1 electron in the second energy level (2s orbital).

Identify Electron Configuration of Nitrogen

Nitrogen (N) has an atomic number of 7, which means it has 7 protons and, when neutral, 7 electrons. The electron configuration of N is 1s² 2s² 2p³. In its ground state, nitrogen has 2 electrons in the first energy level (1s orbital), 2 electrons in the second energy level (2s orbital), and 3 electrons in three different 2p orbitals.

Determine Electron Transfer During Reaction

When lithium and nitrogen react to form lithium nitride (Li₃N), each lithium atom loses one electron to form a Li⁺ ion with a stable 1s² electron configuration. The nitrogen atom gains three electrons to achieve a stable noble gas configuration, similar to neon, resulting in an electron configuration of 1s² 2s² 2p⁶, forming an N³⁻ ion.

Key concepts

Atomic Number and Electron Configuration

Understanding the electron configuration of an element begins with its atomic number, which tells us the number of protons in the nucleus. Significantly, the atomic number also indicates the number of electrons in a neutral atom, since the number of protons and electrons is equal to maintain a neutral charge.

For example, lithium (Li) with an atomic number of 3 has 3 electrons. These electrons occupy specific orbits, known as energy levels, around the nucleus. The electron configuration notation, such as 1s² 2s¹ for lithium, provides a map of where the electrons are located. Lithium's configuration indicates 2 electrons fill the first energy level (s-orbital), and the remaining electron occupies the second level (s-orbital).

Similarly, nitrogen (N), with an atomic number of 7, has 7 electrons. The configuration 1s² 2s² 2p³ for nitrogen means 2 electrons are in the first energy level (s-orbital), 2 more fill the second level (s-orbital), and the final 3 are in different p-orbitals within the second level. This structure profoundly influences how atoms interact in chemical reactions.

Electron Transfer in Chemical Reactions

Chemical reactions often involve the exchange or sharing of electrons between atoms, which alters their electron configurations. In the formation of ionic compounds, atoms can achieve a stable electronic arrangement by transferring electrons to or from other atoms, rather than sharing them.

During the reaction between lithium and nitrogen to form lithium nitride, the lithium atoms lose electrons, each becoming a lithium ion (Li⁺) with a stable electron configuration resembling that of helium. The nitrogen atom undergoes the opposite process; it gains electrons to form a nitride ion (N³⁻), attaining an electron configuration similar to neon's. These changes are crucial as they lead to the formation of ions with full energy levels, a common driver of chemical stability.

Formation of Lithium Nitride

The formation of lithium nitride (Li₃N) is an example of an ionic compound created through electron transfer. For ionic compounds to form, the total charge must be balanced. Lithium, with one electron to spare, forms three Li⁺ ions, each with a single positive charge. Nitrogen, needing three electrons to fill its outer shell, gains those electrons to form one N³⁻ ion. This 1:3 ratio between nitrogen and lithium ions is reflected in the chemical formula Li₃N, emphasizing the role of electron transfer in the formation of stable ionic bonds in compounds.

Lithium nitride is formed through this elegant dance of electrons, where lithium, by shedding its extra valence electron, and nitrogen, by welcoming in additional electrons, both attain a more stable, lower-energy state, indicative of noble gases.

Ionic Bonding and Electron Configurations

Ionic bonding occurs when there is a complete transfer of one or more electrons from one atom to another, leading to the formation of positively and negatively charged ions. The resulting electrostatic attraction between these oppositely charged ions constitutes an ionic bond.

In the context of electron configurations, ionic bonding typically involves an atom with a nearly empty valence shell transferring electrons to an atom with a nearly full valence shell. This enables both atoms to achieve the electron configuration of the closest noble gas, corresponding to a full octet in the valence shell for most elements. The drive towards this stable configuration underpins the formation of ionic compounds like lithium nitride, where the electron configuration of individual ions (Li⁺: 1s², N³⁻: 1s² 2s² 2p⁶) reflects their chemically stable states.