Question

Write full orbital diagrams and indicate the number of unpaired electrons for each element. (a) \(\mathrm{F}\) (b) \(C\) (c) \(\mathrm{Ne}\) (d) \(\mathrm{Be}\)

Short answer

Element F has 1 unpaired electron, element C has 2 unpaired electrons, element Ne has no unpaired electrons, and element Be also has no unpaired electrons.

Step-by-step solution

Determine the Electron Configuration

Find the electron configuration for each element by using the periodic table. Each element's electron configuration will be based on its atomic number, following the order of 's', 'p', 'd', 'f' orbitals according to the Aufbau principle.

Construct the Orbital Diagrams

Draw the orbital diagrams by filling the orbitals according to Hund's Rule and the Pauli Exclusion Principle. Start from the lowest energy orbital and place one electron in each orbital of the same sublevel before pairing them.

Identify Unpaired Electrons

Count the number of electrons in the orbital diagram that are not paired with another electron in the same orbital. These are the unpaired electrons.

Write the Orbital Diagrams for Each Element

For each element, draw the corresponding orbital diagrams and count the number of unpaired electrons. (a) F: 1s^2 2s^2 2p^5, with 1 unpaired electron in the 'p' orbital. (b) C: 1s^2 2s^2 2p^2, with 2 unpaired electrons in the 'p' orbitals. (c) Ne: 1s^2 2s^2 2p^6, with no unpaired electrons, (d) Be: 1s^2 2s^2, with no unpaired electrons.

Key concepts

Electron Configuration

Understanding the electron configuration of an atom is crucial for predicting its chemical behavior. Simply put, electron configuration refers to the distribution of electrons among the energy levels, sublevels, and orbitals of an atom. For example, carbon (C) has an electron configuration of 1s^2 2s^2 2p^2, which means that it has two electrons in its lowest energy level (1s), two in the next level's s orbital (2s), and two in the same level's p orbital (2p).

When writing electron configurations, we follow a specific order determined by the energy levels of the orbitals, usually using the aufbau diagram as a reference. The practice helps in deducing the atom’s valency, possible bonds it can form, and its magnetic properties. Recognizing the importance of electron configuration can aid students in grasping why elements react in various manners.

Aufbau Principle

The Aufbau principle is a fundamental guideline for determining the electron configuration of an element. It states that electrons will fill the lowest available energy orbitals before filling higher ones. Imagine it as the 'building-up' principle where electrons occupy a 'ground floor' before moving up.

The order of filling is as follows: 1s, 2s, 2p, 3s, and so on. Essentially, this means in fluorine (F), with the electron configuration 1s^2 2s^2 2p^5, electrons fill the 1s orbital first, followed by the 2s orbital, and then pile up into the 2p orbitals. The Aufbau principle serves as a pathway for methodically determining how electrons are structured in an atom.

Hund's Rule

Hund's Rule explains how electrons are distributed among orbitals of the same sublevel, such as the p, d, or f orbitals. According to this rule, for orbitals of equal energy, one electron enters each orbital until all orbitals have one electron with parallel spins.

Think of it as people taking seats on a bus; they prefer to sit alone until they must share. In the case of carbon, following Hund's Rule, the 2p electrons are unpaired because each occupies a separate p orbital. This avoids electron-electron repulsion and helps to keep atoms in their lowest possible energy state.

Pauli Exclusion Principle

The Pauli Exclusion Principle is pivotal in the arrangement of electrons in orbitals. It states that no two electrons in an atom can have the same set of four quantum numbers; in other words, an orbital can hold a maximum of two electrons, and they must have opposite spins. This principle explains the distinct electron pairing seen in orbital diagrams.

When looking at beryllium (Be) with an electron configuration of 1s^2 2s^2, we see that the s orbitals each hold two electrons with opposite spins. This principle plays a key role in determining the maximum number of electrons that can inhabit an energy level and helps to predict the chemical properties of an atom.

Unpaired Electrons

Unpaired electrons are those that are alone in an orbital without a partner electron. These electrons are significant because they can contribute to the magnetic properties of an atom and dictate how it will bond with other atoms. For instance, an element like fluorine has one unpaired electron, which is eager to pair up with another electron during bond formation.

Identifying unpaired electrons in an electron configuration or an orbital diagram is essential for understanding chemical reactivity and bonding potential. It also influences the magnetic properties of the substance, as materials with unpaired electrons can exhibit magnetic behavior.