Question

Write the full electron configuration for each element. a. C b. P c. Ar d. Na

Short answer

a. Carbon (C): 1s² 2s² 2p², b. Phosphorus (P): 1s² 2s² 2p⁶ 3s² 3p³, c. Argon (Ar): 1s² 2s² 2p⁶ 3s² 3p⁶, d. Sodium (Na): 1s² 2s² 2p⁶ 3s¹.

Step-by-step solution

Carbon (C) Electron Configuration

To write the electron configuration for Carbon (atomic number 6), we start at Hydrogen and follow the order of orbitals based on the Aufbau principle: 1s, 2s, 2p, etc. Carbon has 6 electrons to place in the orbitals: 1s will get 2 electrons, 2s will also get 2 electrons, and 2p gets the remaining 2 electrons. Thus, the electron configuration is 1s² 2s² 2p².

Phosphorus (P) Electron Configuration

For Phosphorus (atomic number 15), apply the same principles: 1s² 2s² 2p⁶ fill the first and second orbitals, and then we fill 3s² and place the remaining 3 electrons in 3p orbital, resulting in 3p³. Therefore, the full configuration is 1s² 2s² 2p⁶ 3s² 3p³.

Argon (Ar) Electron Configuration

Argon (atomic number 18) follows the same order: after filling 1s, 2s, 2p, and 3s orbitals, and 3p obtains the last 6 electrons to be fully filled due to its atomic number. So, the configuration is 1s² 2s² 2p⁶ 3s² 3p⁶.

Sodium (Na) Electron Configuration

Sodium (atomic number 11) has its first 10 electrons filling 1s² 2s² 2p⁶. The 11th electron goes into the next orbital, which is 3s. The configuration for Sodium is 1s² 2s² 2p⁶ 3s¹.

Key concepts

Aufbau Principle

The Aufbau principle, which translates to 'building-up' in German, is a foundational concept used to determine the electron configuration of atoms. It states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. Think of it as a methodical way of organizing a classroom with students taking their seats starting from the front row, which is closest to the board and therefore the most accessible.

When applying the Aufbau principle as seen in the exercise, Carbon, with an atomic number of 6, starts filling electrons from the lowest energy orbital, 1s, moving subsequently to 2s and 2p. This approach simplifies the process of deducing the correct configuration for any element on the periodic table.

Orbital Filling Order

The concept of orbital filling order goes hand in hand with the Aufbau principle and dictates the sequence in which orbitals are filled. Electrons don't randomly occupy positions around the nucleus; they follow a specific order based on subshell energy. The order follows the sequence: 1s, 2s, 2p, 3s, 3p, and continues progressively through the periodic table.

In our exercise, after filling the 1s and 2s orbitals, Phosphorus (P) places electrons in the 2p orbitals, continues to the 3s, and finally into the 3p orbital. This sequential filling is crucial for understanding an atom’s electronic structure and its resultant chemical behavior. A useful mnemonic device often employed is the 'n+ℓ rule,' where orbitals are filled in order of increasing n+ℓ values, with 'n' being the principal quantum number and ℓ the azimuthal quantum number.

Atomic Number

The atomic number is a term integral to the study of chemistry and atomic theory. It is defined as the number of protons found in the nucleus of an atom and, by extension, also represents the number of electrons in a neutral atom. The atomic number ultimately determines an element's identity and its position on the periodic table.

As per the step by step solution in the exercise, Sodium (Na) with an atomic number of 11 contains 11 protons and, when uncharged, has 11 electrons as well. Knowing the atomic number allows you to count out the electrons needed and apply the Aufbau principle and orbital filling order to write the electron configuration. For example, elements with higher atomic numbers will have more complex electron configurations, often involving a larger number of orbitals.