Problem 29 - Chemistry: Principles and Reactions

Question

Write the ground state electron configuration for (a) \(\mathrm{N}\) (b) Na (c) Ne (d) Ni (e) Si

Step-by-Step Solution

Answer

Provide the ground state electron configurations using noble gas notation for the following elements: (a) Nitrogen (N), (b) Sodium (Na), (c) Neon (Ne), (d) Nickel (Ni), and (e) Silicon (Si).

Step 1: Identify the atomic number of the given elements.

Using the periodic table, identify the atomic number of each element, which represents the number of protons and electrons in a neutral atom. (a) N (Nitrogen) has an atomic number of 7. (b) Na (Sodium) has an atomic number of 11. (c) Ne (Neon) has an atomic number of 10. (d) Ni (Nickel) has an atomic number of 28. (e) Si (Silicon) has an atomic number of 14.

Step 2: Determine the electron configuration for each element using Aufbau principle.

Starting with the lowest energy level (1s) and following the Aufbau principle, arrange the electrons into the allowed subshells until the number of electrons equals the atomic number of the element. (a) N (7 electrons): 1s², 2s², 2p³ (b) Na (11 electrons): 1s², 2s², 2p⁶, 3s¹ (c) Ne (10 electrons): 1s², 2s², 2p⁶ (d) Ni (28 electrons): 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d⁸ (e) Si (14 electrons): 1s², 2s², 2p⁶, 3s², 3p²

Step 3: Write the ground state electron configurations using the noble gas notation.

To simplify the electron configuration, replace the core electron configuration with the preceding noble gas in brackets. (a) N: [He] 2s² 2p³ (b) Na: [Ne] 3s¹ (c) Ne: [He] 2s² 2p⁶ (d) Ni: [Ar] 4s² 3d⁸ (e) Si: [Ne] 3s² 3p²

Key Concepts

Aufbau Principle

Understanding the Aufbau principle is essential for determining an atom's electron configuration. This principle guides us to fill up an atom's energy levels with electrons starting from the lowest energy orbitals to the higher ones in a step-by-step manner. The sequence of orbitals starts at 1s, followed by 2s, 2p, 3s, and so forth, following a specific order based on their increasing energy.

Think of it as filling up seats in a theater, where you have to fill the front row seats before moving to the next rows. Similarly, electrons occupy available seats

Atomic Number

The atomic number is fundamentally important in understanding electron configurations. It's the number that designates the unique identity of an element, and also equals the number of protons found in the nucleus of an atom. In a neutral atom, this number also equals the number of electrons. For instance, carbon has an atomic number of 6, meaning it has 6 protons and, if neutral, 6 electrons.

On the periodic table, elements are arranged in ascending order based on their atomic numbers. This number isn't just a label; it essentially determines the chemical properties of the element because it influences how the atom's electrons are arranged.

Noble Gas Notation

The noble gas notation simplifies writing an element's electron configuration by using the electron configuration of the nearest noble gas that precedes the element on the periodic table. Noble gases are elements like helium (He), neon (Ne), and argon (Ar), which have their outer energy levels fully occupied by electrons, creating a very stable configuration.

By representing the already filled electron configuration of a noble gas, we create a shorthand notation for the rest of the element's configuration. For instance, the noble gas notation for Chlorine (Cl) with an atomic number of 17 is [Ne] 3s² 3p⁵, where [Ne] represents the configuration of Neon which has an atomic number of 10.

Ground State

The ground state refers to the lowest energy arrangement of electrons in an atom. This is the most stable state where electrons are located in the closest possible orbitals to the nucleus following the Aufbau principle. Electrons prefer to be in the ground state because it requires the least amount of energy.

When working with electron configurations, we're usually dealing with atoms in their ground state unless otherwise specified. For example, the ground state electron configuration of Oxygen (O), with an atomic number of 8, is 1s² 2s² 2p⁴, with all electrons in the lowest possible energy levels.

Periodic Table

The periodic table is not only a chart of the elements but also a powerful tool for predicting the chemical behavior of atoms. The table is arranged by ascending atomic numbers and organized in such a way that elements with similar electron configurations and therefore similar chemical properties line up in columns known as groups.

For example, all alkali metals reside in the first column and have a single electron in their outermost shell, which they readily lose to form cations. The table's layout also reflects the repeating pattern of chemical properties, known as the periodic law. Mastering the layout of the periodic table is paramount to understanding how elements interact and relate to one another.