Problem 16 - Chemistry A Guided Inquiry

Question

Based on its position in the periodic table, what is the valence shell and what is the core charge for \(\mathrm{C}\). Explain your reasoning.

Step-by-Step Solution

Answer

For element Carbon (C), the valence shell is the second energy level (n=2) with the electron configuration \(2s^2 2p^2\). Its core charge is +4, which is derived by subtracting the 2 electrons in the first shell from Carbon's atomic number (+6).

Step 1: Identify the element

The element in question is Carbon, which is the 6th element in the periodic table. According to the periodic table, Carbon is in period 2 and group 14 standard notation (or group IV using old IUPAC notation).

Step 2: Determine the electron configuration

We have to analyze the electron configuration of Carbon. The electron configuration of an atom describes the distribution of electrons to the shell and subshell. For Carbon (Atomic number: 6), the electron configuration is \(1s^2 2s^2 2p^2\). This shows Carbon has 2 electrons in the 1s, 2s and 2p subshells.

Step 3: Define the valence shell and Core charge

The valence shell of an atom is its highest-energy, outmost shell. For Carbon, the valence shell is the second energy level (n=2) where 4 electrons (2s^2 2p^2) are present. The core charge refers to the effective nuclear charge experienced by the valence shell electrons. It can be calculated by subtracting the number of shielding electrons (non-valence electrons) from the atomic number. For Carbon, the core charge is +4, which is obtained by subtracting the 2 electrons in the first shell (1s^2) from the atomic number of Carbon (+6).

Key Concepts

Understanding the Periodic Table

The periodic table is a systematic arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations, and recurring chemical properties. Elements are listed in order of increasing atomic number, which is the number of protons in an element's nucleus, giving each its unique identity.

Elements are also arranged into rows called 'periods' and columns known as 'groups'. Elements in the same period have the same number of atomic orbitals. For example, carbon is in the second period, indicating it has two atomic orbitals. Groups contain elements with similar properties and the same number of electrons in their outer valence shell. Carbon's position in group 14 signifies it has four valence electrons.

The periodic table is integral in predicting the characteristics of elements based on their position, making it essential for understanding concepts related to the valence shell and core charge.

Electron Configuration

Electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. Essential to the structure of the periodic table, electron configuration informs the chemical behavior of an element.

For instance, carbon has the electron configuration of 1s^2 2s^2 2p^2. This notation shows that carbon has two shells, with the inner shell (1s) holding two electrons, and four electrons in the outer shell (2s and 2p). The electrons in the outer shell are called valence electrons and are crucial for chemical bond formation. Understanding the electron arrangement allows chemists to predict an element's reactivity, the types of bonds it can form, and its behavior in chemical reactions.

Effective Nuclear Charge

The effective nuclear charge is a concept in chemistry that refers to the net positive charge experienced by an electron in a multi-electron atom. The reason the full positive charge of the nucleus is not felt by the valence electrons is due to shielding by the core electrons.

To find the effective nuclear charge, or core charge, we subtract the number of core (inner shell) electrons from the atomic number, which represents the number of protons. For carbon, with an atomic number of 6 and 2 electrons in its inner shell, the effective nuclear charge felt by the valence electrons will be +6 (atomic number) - 2 (core electrons) = +4. This positive charge attracts the valence electrons towards the nucleus, playing a significant role in the chemistry of the atom, influencing atomic size, ionization energy, and the atom's overall stability.