Question

Select the member of group 4 \(\mathrm{A}\) that best fits each description: (a) has the lowest first ionization energy, ( b) is found in oxidation states ranging from \(-4\) to \(+4,(\mathbf{c})\) is most abundant in Earth's crust.

Short answer

(a) Lead (Pb) has the lowest first ionization energy. (b) Carbon (C) is found in oxidation states ranging from -4 to +4. (c) Silicon (Si) is most abundant in Earth's crust.

Step-by-step solution

Identify Group 4A Elements

Group 4A, also known as Group 14, contains the following elements: Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), and Lead (Pb). These elements share some properties, such as having four valence electrons and forming covalent bonds.

Determine the element with the lowest first ionization energy

First ionization energy is the amount of energy required to remove the first electron from an atom of an element. Generally, ionization energies decrease down a group of the periodic table because the atomic size increases, resulting in a weaker attraction between the electrons and the nucleus. In Group 4A, the ionization energy decreases in the following order: C > Si > Ge > Sn > Pb. Therefore, Lead (Pb) has the lowest first ionization energy. Answer: (a) Lead (Pb).

Determine the element with oxidation states ranging from -4 to +4

Carbon (C) is the element with the oxidation states ranging from -4 to +4. Carbon has four valence electrons and can achieve a stable octet by losing, gaining, or sharing up to 4 electrons. Carbon is known to form various compounds and allotropes, including organic compounds and inorganic compounds like carbides, carbonates, and oxides, where it can have different oxidation states. Answer: (b) Carbon (C).

Determine the most abundant element in Earth's crust

Silicon (Si) is the most abundant element in Earth's crust, representing about 28% of its total mass. Silicon is an essential component of rocks, such as silicates and silicon dioxide (sand). Additionally, silicon is widely used in technology, such as in semiconductors and solar cells. Answer: (c) Silicon (Si).

Key concepts

First Ionization Energy

Ionization energy refers to the amount of energy required to remove an electron from an atom in its gaseous state. The first ionization energy specifically concerns the removal of the first electron, which is typically the most loosely held. As you move down a group in the periodic table, the first ionization energy decreases. This is because as the atomic number increases, the electrons are found in higher energy levels, farther from the nucleus, and are therefore held less tightly due to the larger atomic radius and shielding effect of inner electrons.

In Group 4A, going from Carbon (C) to Lead (Pb), the size of the atoms increases, which explains why Lead has the lowest first ionization energy in the group. To visualize this, consider how it becomes easier to detach an apple from a branch if the apple is hanging from a taller, more extended branch; similarly, outer electrons can be removed more easily from larger atoms with less energy. Such comparisons can make these complex concepts more accessible to students.

Oxidation States

The concept of oxidation states describes the degree of oxidation of an element, which simply can be understood as the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Elements in Group 4A have four valence electrons and can exhibit various oxidation states, which depends on with whom they share or transfer electrons.

For instance, Carbon, which sits at the top of Group 4A, shows the versatility in oxidation states ranging from -4 to +4. It can form four covalent bonds as in methane, where it has a -4 state, or it can accept four electrons as in carbon tetrachloride, where it has a +4 oxidation state. The varying ability of carbon to engage in such diverse chemical behavior explains its central role in organic chemistry. Similarly, the ease with which carbon can shift between oxidation states is foundational to life on Earth, as it is integral to processes such as cellular respiration and photosynthesis, illustrating the profound real-world implications of these principles.

Earth's Crust Abundance

The abundance of elements in Earth's crust is a measure of how common certain elements are in the planet's outermost layer. Silicon, one of the Group 4A elements, stands out due to its significant abundance and is the second most plentiful element in the Earth's crust after oxygen.

As a crucial component of minerals like sand and common silicates, silicon's prevalence makes it a fundamental part of rocks and soil. From a practical standpoint, its abundance makes it a cornerstone of the construction industry for materials such as concrete and glass. Moreover, due to its semiconducting properties, it is integral to the technology sector for producing computer chips and photovoltaic cells for solar panels, highlighting its economic and technological importance. Acknowledging its abundance helps students understand why silicon technology is so widespread and crucial. By linking these concepts to tangible, real-world materials, students may find it easier to relate to and remember the information presented to them.