Determining The Oxidation State Of Magnesium In Mg(OH)₂

The reaction we're diving into today, guys, is this one:

$Mg(s) + 2 H_2 O(l) \rightarrow Mg(OH)_2(s) + H_2(g)$

This chemical equation illustrates a fascinating process where solid magnesium (Mg) reacts with liquid water (H₂O) to produce solid magnesium hydroxide (Mg(OH)₂) and hydrogen gas (H₂). It's a classic example of a redox reaction, where electrons are transferred between reactants, leading to changes in oxidation states. Oxidation states, also known as oxidation numbers, are crucial for understanding how electrons are distributed within a compound and how atoms interact with each other. So, let's break down the oxidation states of each element involved in this reaction to truly grasp what's happening at the atomic level. Understanding oxidation states is fundamental in chemistry, as it helps us predict and explain the behavior of elements in various chemical reactions and compounds. In the context of this specific reaction, determining the oxidation state of magnesium in magnesium hydroxide is key to understanding the electron transfer process and the overall chemical transformation. When we look at the reactants, we see magnesium in its elemental form (Mg(s)). In its elemental state, an element has an oxidation state of 0. This makes sense because there's no charge associated with a pure element; it hasn't gained or lost any electrons. Water (H₂O) is a bit more complex. Oxygen is more electronegative than hydrogen, meaning it attracts electrons more strongly. As a result, oxygen typically has an oxidation state of -2, while each hydrogen atom has an oxidation state of +1. Now, let's shift our focus to the products. Hydrogen gas (H₂) is again in its elemental form, so its oxidation state is 0, just like elemental magnesium. The real star of the show, though, is magnesium hydroxide (Mg(OH)₂). This compound holds the key to understanding how magnesium's oxidation state changes during the reaction, which will lead us to the answer to our main question. To figure out magnesium's oxidation state in Mg(OH)₂, we need to consider the oxidation states of the other elements present. As we already established, oxygen usually has an oxidation state of -2, and hydrogen has an oxidation state of +1. The hydroxide ion (OH⁻) as a whole has a charge of -1, which is the sum of the oxidation states of oxygen (-2) and hydrogen (+1). In Mg(OH)₂, there are two hydroxide ions, so their total negative charge is -2. For the compound to be neutral (which it is, since there's no overall charge indicated), the magnesium ion must balance out this -2 charge. Therefore, magnesium must have an oxidation state of +2 in Mg(OH)₂. This means that magnesium has lost two electrons during the reaction, transitioning from an oxidation state of 0 in its elemental form to +2 in magnesium hydroxide. This loss of electrons is what we call oxidation. By losing electrons, magnesium becomes more positively charged. This change in oxidation state is a direct result of the chemical reaction with water, where magnesium donates electrons to form the hydroxide compound and hydrogen gas. This process is crucial in understanding the overall electron transfer that occurs during the reaction, which is a hallmark of redox reactions. The oxidation state of +2 for magnesium in Mg(OH)₂ is consistent with its position in the periodic table. Magnesium belongs to Group 2, also known as the alkaline earth metals, which are known for readily losing two electrons to form +2 ions. This behavior is driven by the stability gained when magnesium achieves a noble gas electron configuration. By losing two electrons, magnesium attains the same electron arrangement as neon, a stable noble gas, which explains its tendency to form +2 ions in chemical compounds. In the formation of magnesium hydroxide, magnesium's +2 oxidation state allows it to bond with two hydroxide ions (OH⁻), each carrying a -1 charge. This creates a stable ionic compound, where the electrostatic attraction between the positively charged magnesium ion and the negatively charged hydroxide ions holds the compound together. This ionic bonding is characteristic of many metal hydroxides, reflecting the strong interactions between metal cations and hydroxide anions. The change in magnesium's oxidation state from 0 to +2 highlights the fundamental nature of redox reactions. In this specific reaction, magnesium is oxidized, meaning it loses electrons, while water is reduced, meaning it gains electrons. The electrons lost by magnesium are transferred to water, leading to the formation of hydrogen gas and magnesium hydroxide. This electron transfer is the driving force behind the chemical transformation, making it a prime example of how oxidation and reduction processes work hand in hand. Understanding the oxidation states of elements in a chemical reaction provides valuable insights into the underlying electron transfer mechanisms and the resulting chemical changes. In the case of magnesium reacting with water, the oxidation of magnesium and the reduction of water are essential components of the overall reaction, illustrating the dynamic interplay between electron donors and electron acceptors in chemical transformations.

Determining Magnesium's Oxidation State in Mg(OH)₂

Okay, so the big question is: what's the oxidation state of Mg in Mg(OH)₂? This might sound tricky, but trust me, it's totally doable! To figure this out, we need to remember some key rules about oxidation states. Basically, oxidation states tell us how many electrons an atom has gained, lost, or shared when it forms a chemical bond. Think of it like keeping track of electrons in a chemical partnership. When we dive into the world of oxidation states, it's like unraveling a puzzle. Each element follows certain rules, and by understanding these rules, we can piece together the oxidation state of any element within a compound. Let's start with the basics. Elements in their pure, uncombined form, like solid magnesium (Mg(s)) or hydrogen gas (H₂(g)), always have an oxidation state of 0. This makes sense because, in their elemental state, they haven't formed any bonds or exchanged any electrons. But when elements combine to form compounds, things get a bit more interesting. The oxidation state of an element in a compound reflects how its electron environment has changed due to bonding. Some elements have predictable oxidation states. For instance, oxygen is a bit of an electron hog, and it usually has an oxidation state of -2 in compounds. Hydrogen, on the other hand, tends to be more generous with its electrons and usually has an oxidation state of +1. These predictable oxidation states serve as our anchors when determining the oxidation states of other elements in a compound. In the case of magnesium hydroxide (Mg(OH)₂), we can leverage these anchors to figure out the oxidation state of magnesium. We know that the overall charge of a neutral compound is zero. This means that the sum of the oxidation states of all the atoms in the compound must equal zero. In Mg(OH)₂, we have one magnesium atom, two oxygen atoms, and two hydrogen atoms. We already know the oxidation states of oxygen and hydrogen, so we can use this information to solve for the oxidation state of magnesium. Each oxygen atom contributes a -2 oxidation state, and each hydrogen atom contributes a +1 oxidation state. Since there are two hydroxide (OH⁻) ions in Mg(OH)₂, the total negative charge from the oxygen atoms is -4 (2 oxygen atoms x -2), and the total positive charge from the hydrogen atoms is +2 (2 hydrogen atoms x +1). Now, we can set up a simple equation to calculate the oxidation state of magnesium. Let's call magnesium's oxidation state x. The equation looks like this: x + 2(+1) + 2(-2) = 0 This equation represents the sum of the oxidation states of all the atoms in Mg(OH)₂, which must equal zero for a neutral compound. Simplifying the equation, we get: x + 2 - 4 = 0 x - 2 = 0 Solving for x, we find that: x = +2 So, the oxidation state of magnesium in Mg(OH)₂ is +2. This means that magnesium has lost two electrons when it forms this compound. Magnesium's +2 oxidation state is consistent with its position in the periodic table. As a Group 2 element, magnesium readily loses two electrons to achieve a stable electron configuration, similar to that of a noble gas. This tendency to lose two electrons is what makes magnesium form +2 ions in its compounds. This +2 oxidation state also explains why magnesium hydroxide is formed in the first place. Magnesium, with its +2 charge, is attracted to the negative charges of the hydroxide ions (OH⁻), which have an overall charge of -1. The electrostatic attraction between the positively charged magnesium ion and the negatively charged hydroxide ions leads to the formation of a stable ionic compound. Understanding the oxidation state of magnesium in Mg(OH)₂ gives us a deeper insight into the chemical bonding and interactions within the compound. It helps us appreciate how magnesium's electron configuration and its position in the periodic table dictate its chemical behavior. So, when you encounter compounds like magnesium hydroxide, remember that the oxidation states of the elements involved are key to understanding their chemical properties and reactivity. This concept extends far beyond just this specific example. The ability to determine oxidation states is a fundamental skill in chemistry, allowing us to analyze and predict the behavior of elements in countless chemical reactions and compounds. From simple ionic compounds to complex organic molecules, oxidation states provide a valuable framework for understanding electron transfer and chemical bonding. So, mastering this skill will undoubtedly serve you well in your journey through the fascinating world of chemistry.

The Correct Answer and Why

So, after all that digging, we know the oxidation state of Mg in Mg(OH)₂ is +2. That means the correct answer is D. This makes sense because magnesium, being in Group 2 of the periodic table, loves to lose two electrons to get a stable electron configuration. And when it loses those electrons, it gets a +2 charge, right? Understanding why +2 is the correct answer involves delving into the fundamental principles of oxidation states and how they reflect the electronic behavior of elements in chemical compounds. As we've discussed, oxidation states provide a way to track the number of electrons an atom has gained, lost, or shared when it forms a chemical bond. This concept is crucial for understanding redox reactions, where electrons are transferred between reactants, leading to changes in oxidation states. In the context of magnesium hydroxide (Mg(OH)₂), the +2 oxidation state of magnesium signifies that it has lost two electrons. This electron loss is directly related to magnesium's position in the periodic table. Magnesium belongs to Group 2, also known as the alkaline earth metals. Elements in this group have two valence electrons, meaning they have two electrons in their outermost electron shell. These valence electrons are the ones that participate in chemical bonding. To achieve a stable electron configuration, magnesium tends to lose these two valence electrons, resulting in the formation of a +2 ion (Mg²⁺). By losing two electrons, magnesium attains the same electron arrangement as neon, a noble gas, which has a stable, filled electron shell. This drive to achieve a noble gas electron configuration is a key factor in determining the chemical behavior of many elements, including magnesium. In the formation of magnesium hydroxide, magnesium's +2 charge allows it to form ionic bonds with two hydroxide ions (OH⁻). Each hydroxide ion carries a -1 charge, resulting from the combination of oxygen (typically -2) and hydrogen (+1). The electrostatic attraction between the positively charged magnesium ion and the negatively charged hydroxide ions leads to the formation of a stable ionic compound, where the ions are held together by strong electrostatic forces. This ionic bonding is characteristic of many metal hydroxides, reflecting the tendency of metals to lose electrons and form positive ions. The fact that magnesium readily forms a +2 ion also explains why options A, B, and C are incorrect. Option A, 0, would only be correct if magnesium were in its elemental form, not bonded to other elements in a compound. Option B, -2, suggests that magnesium has gained two electrons, which is the opposite of its typical behavior. Option C, +1, would imply that magnesium has only lost one electron, which is less stable than losing two electrons to achieve a noble gas electron configuration. Therefore, understanding magnesium's position in the periodic table and its tendency to lose two electrons is essential for arriving at the correct answer of +2. This example highlights the importance of connecting oxidation states to the electronic structure of elements. By understanding the electronic configurations of atoms and how they change during chemical reactions, we can predict and explain the oxidation states of elements in various compounds. This skill is fundamental in chemistry, allowing us to analyze and interpret a wide range of chemical phenomena. So, when you encounter questions about oxidation states, remember to consider the element's position in the periodic table, its electronic configuration, and its tendency to gain or lose electrons. These factors will guide you towards the correct answer and provide a deeper understanding of the underlying chemical principles. This approach not only helps in answering specific questions but also fosters a more comprehensive understanding of chemical bonding and reactivity.

I hope this breakdown helps you understand oxidation states a bit better! Let me know if you have any more questions, guys!