Question

Which atom \((X)\) is indicated by the following configuration? \(X \rightarrow[\mathrm{Ne}] 3 s^{2} 3 p^{3}\) (a) Nitrogen (b) Chlorine (c) Phosphorus (d) Sulphur

Short answer

The atom with the given electron configuration \(X \rightarrow[\mathrm{Ne}] 3s^{2} 3p^{3}\) is phosphorus (c).

Step-by-step solution

Identify the Noble Gas Configuration

The given electron configuration starts with the noble gas neon (Ne), which means that the electron configuration is being abbreviated by showing the configuration up to neon first. Neon has an atomic number of 10, which corresponds to its number of electrons.

Add Outer Electrons

After the noble gas neon, the configuration shows an additional 3s^2 and 3p^3 electrons. This means there are 2 electrons in the 3s orbital and 3 electrons in the 3p orbitals. To find the total number of electrons for the atom X, add the electrons in the 3s and 3p orbitals to the 10 electrons that neon has: 10 (Ne) + 2 (3s) + 3 (3p) = 15 electrons in total.

Determine the Atom

An atom with 15 electrons is phosphorus (P). This is because phosphorus is the 15th element on the periodic table which corresponds to its atomic number.

Key concepts

Noble Gas Configuration

Understanding the noble gas configuration simplifies how we represent the electron configuration for elements. Noble gases, like neon (Ne), argon (Ar), or helium (He), have complete electron shells and are chemically inert. When writing configurations, we often use a noble gas as a shorthand to represent all the electrons up to that point, as they form a stable foundation.

For instance, the configuration \(\mathrm{[Ne]} 3s^2 3p^3\) indicates that the element has the same electron configuration as neon plus the additional electrons in the 3s and 3p orbitals. This shortcut can be very helpful when dealing with elements that have a large number of electrons. Identifying this foundation allows students to calculate the total electron count of the element more efficiently, leading them to the correct identification of the element in question.

Orbital Electrons

Electrons orbit the nucleus of an atom in regions known as orbitals. These orbitals are systematically filled according to certain rules, which include the Pauli Exclusion Principle and Hund's Rule.

In the configuration \(\mathrm{[Ne]} 3s^2 3p^3\), the numbers represent the energy levels, 's' and 'p' designate the type of orbital, and the superscript numbers indicate how many electrons are in those orbitals.

• \(3s^2\) means there are 2 electrons in the 3s orbital.
• \(3p^3\) means 3 electrons are in the 3p orbital.

Understanding how to read these configurations enables students to visualize the distribution of electrons around the nucleus, which is crucial for predicting an element’s chemical behavior.

Periodic Table

The periodic table is a comprehensive chart that organizes all known elements according to their atomic number, which is equal to the number of protons (and electrons in a neutral atom). Elements are also grouped by similar properties into columns called 'groups' and into rows called 'periods' based on their electron configurations.

The position of an element provides valuable information about its reactivity, the types of bonds it will form, and its state at room temperature. For our exercise, knowing that phosphorus is the 15th element on the periodic table means it has an atomic number of 15, correlating to its total electron count. This real-world logic reinforces the steps of the solution, wherein counting the total electron number confirms the identity of phosphorus and aids in understanding the overall structure and use of the periodic table.