Problem 87 - Chemistry Matter and Change

Question

What element is represented by each electron configuration? $$\begin{array}{l}{\text { a. } 1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{p}^{5}} \\ {\text { b. }[\mathrm{Ar}] 4 \mathrm{s}^{2}} \\ {\text { c. }[\mathrm{Xe}] 6 \mathrm{s}^{2} \mathrm{4f}^{4}} \\ {\text { d. }[\mathrm{Kr}] 5 \mathrm{s}^{2} 4 \mathrm{d}^{10} \mathrm{5p}^{4}} \\ {\text { e. }[\mathrm{Rn}] 7 \mathrm{s}^{2} 5 \mathrm{f}^{13}} \\ {\text { f. } 1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{s}^{2} 3 \mathrm{p}^{6} 4 \mathrm{s}^{2} 3 \mathrm{d}^{10} 4 \mathrm{p}^{5}}\end{array}$$

Step-by-Step Solution

Answer

a) F (Fluorine), b) Ca (Calcium), c) Nd (Neodymium), d) Te (Tellurium), e) Md (Mendelevium), f) Br (Bromine).

Step 1: Understand Electron Configuration

Electron configuration shows the distribution of electrons in an atom's orbitals. Each notation such as \(1s^2\) indicates electrons in specific orbitals. Subshells are filled in order of increasing energy levels: \(s\), \(p\), \(d\), \(f\). Notation involves the type of orbital and the number of electrons in that orbital.

Step 2: Analyze Configuration a

Configuration a is \(1s^2 2s^2 2p^5\). The total number of electrons is \(2+2+5=9\). The 9th element in the periodic table is fluorine (F).

Step 3: Analyze Configuration b

Configuration b is \([\text{Ar}] 4s^2\). Argon \([\text{Ar}]\) has 18 electrons, so adding two more from \(4s^2\) gives us 20. The 20th element is calcium (Ca).

Step 4: Analyze Configuration c

Configuration c is \([\text{Xe}] 6s^2 4f^4\). Xenon \([\text{Xe}]\) has 54 electrons. Adding \(6s^2\) and \(4f^4\) gives \(54+2+4=60\). The 60th element is neodymium (Nd).

Step 5: Analyze Configuration d

Configuration d is \([\text{Kr}] 5s^2 4d^{10} 5p^4\). Krypton \([\text{Kr}]\) has 36 electrons. Adding \(12\) electrons from \(5s^2 4d^{10} 5p^4\) gives \(36+12=48\). The 48th element is cadmium (Cd), incorrect in initial calculation, should be tellurium (Te). Correction included.

Step 6: Analyze Configuration e

Configuration e is \([\text{Rn}] 7s^2 5f^{13}\). Radon \([\text{Rn}]\) has 86 electrons. Adding \(15\) electrons from \(7s^2 5f^{13}\) results in \(86+2+13=101\). The 101st element is mendelevium (Md).

Step 7: Analyze Configuration f

Configuration f is \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^5\). Count electrons: \(2+2+6+2+6+2+10+5=35\). The 35th element is bromine (Br).

Key Concepts

The Periodic Table

The periodic table is a structured chart that organizes all known chemical elements. These elements are listed by increasing atomic number, which represents the number of protons in an atom of the element. The table is arranged in rows and columns that highlight periodic trends and similarities among elements.

The rows of the periodic table are called periods, and they represent elements with the same principal energy level for their electrons. The columns, or groups, contain elements that have similar chemical properties due to their electron configurations. Understanding the organization of the periodic table helps us predict how an element will behave and react with others.

• Periods: Indicate energy levels of electrons.
• Groups: Indicate similar properties due to electron configuration.

Elements can be identified by their position on the periodic table, which is crucial for deducing their electron configurations.

Elements Identification

Elements can be identified using their unique electron configurations, which specify the distribution of electrons across different orbitals. By counting the total number of electrons, we can identify the element based on its position in the periodic table.

Every electron configuration consists of numbers and letters that denote the energy levels and types of orbitals (subshells) occupied by electrons. For example, the element with the electron configuration of \( 1s^2 2s^2 2p^5 \) is fluorine, which has a total of nine electrons. This allows us to spot it as the ninth element in the periodic table. Correct element identification is key to understanding the chemical behavior and properties linked to an electron configuration.

Atomic Structure

The atomic structure of an element consists of a nucleus made of protons and neutrons, surrounded by electrons in various orbitals. The number of protons uniquely identifies each element: this is its atomic number. Electrons orbit the nucleus at different energy levels, and their arrangements dictate the element's reactivity and properties.

The core part of an element's atomic structure is defined by its electron configuration. This reveals how electrons are arranged and, consequently, how the element will form bonds with others. Elements like krypton have a core electron configuration represented as \[ \text{[Kr]} \]\, indicating a stable, full set of energy levels up to krypton, upon which further electrons are added, as seen in different configurations.

Electron Orbitals

Electron orbitals describe regions around an atom's nucleus where electrons are likely to be found. These orbitals are classified into types: \( s \), \( p \), \( d \), and \( f \), each with a distinct shape and capacity to hold electrons.

Understanding orbital types is crucial. Each orbital fits a specific number of electrons: \( s \) orbitals hold 2, \( p \) orbitals hold 6, \( d \) orbitals hold 10, and \( f \) orbitals hold 14. Electrons fill these orbitals in an order defined by increasing energy levels, following the "Aufbau Principle". Each type also corresponds to a different section of the periodic table. For instance, the \( d \)-block elements are transition metals, known for having electrons in \( d \) orbitals. By understanding electron orbitals, one can deduce how electrons are arranged in atoms, which is vital for identifying unknown elements from their electron configurations.