Problem 69 - Chemistry: The Central Science in SI Units, Global Edition

Question

Write the formulas for the following compounds, and indicate the oxidation state of the group 14 element or of boron in each: (a) silane, \((\mathbf{b})\) germanium dichloride, (c) \(\operatorname{tin}(\mathrm{II})\) sulfide, \((\mathbf{d})\) sodium borohydride, \((\mathbf{e})\) lead(IV) nitrate, \((\mathbf{f})\) tin dioxide.

Step-by-Step Solution

Answer

(a) Silane: Formula - SiH4, Oxidation state of Si: 0 (b) Germanium dichloride: Formula - GeCl2, Oxidation state of Ge: +2 (c) Tin(II) sulfide: Formula - SnS, Oxidation state of Sn: +2 (d) Sodium borohydride: Formula - NaBH4, Oxidation state of B: +3 (e) Lead(IV) nitrate: Formula - Pb(NO3)4, Oxidation state of Pb: +4 (f) Tin dioxide: Formula - SnO2, Oxidation state of Sn: +4

Step 1: (a) Silane formula and oxidation state

Silane is a compound with the chemical formula SiH4. In this molecule, silicon (Si) is bonded to four hydrogen (H) atoms. Silicon's oxidation state in silane is 0, as it has gained no electrons.

Step 2: (b) Germanium dichloride formula and oxidation state

Germanium dichloride has the chemical formula GeCl2. In this compound, germanium (Ge) is bonded to two chlorine atoms (Cl). To determine the oxidation state, we note that each chlorine atom has an oxidation state of -1, thus total oxidation state for the two chlorine atoms is -2. The germanium atom balances this by having an oxidation state of +2.

Step 3: (c) Tin(II) sulfide formula and oxidation state

Tin(II) sulfide is a compound that includes tin in its +2 oxidation state. The chemical formula for tin(II) sulfide is SnS. The oxidation state of tin (Sn) in this compound is given as +2.

Step 4: (d) Sodium borohydride formula and oxidation state

Sodium borohydride has the chemical formula NaBH4. In this compound, boron (B) is bonded to four hydrogen atoms in the form of hydride (H-) ions. Sodium (Na) is present as a cation with its +1 oxidation state, balancing the charges. Since the four hydride anions (H-) contribute a charge of -4, boron's oxidation state must be +3.

Step 5: (e) Lead(IV) nitrate formula and oxidation state

Lead(IV) nitrate is a compound with lead in its +4 oxidation state. The chemical formula for lead(IV) nitrate is Pb(NO3)4. The oxidation state of lead (Pb) in this compound is given as +4.

Step 6: (f) Tin dioxide formula and oxidation state

Tin dioxide has the chemical formula SnO2. In this compound, tin (Sn) is bonded to two oxygen atoms (O). To determine the oxidation state, we note that each oxygen atom has an oxidation state of -2, thus the total oxidation state for the two oxygen atoms is -4. The tin atom balances this by having an oxidation state of +4.

Key Concepts

Oxidation States

Oxidation states, sometimes called oxidation numbers, are a crucial concept in understanding chemical reactions, particularly in inorganic chemistry. An oxidation state indicates the degree of oxidation of an atom in a molecule. It represents the hypothetical charge an atom would have if all its bonds were ionic. Here's how to determine oxidation states:

• Atoms in their elemental form have an oxidation state of 0.
• For simple ions, the oxidation state is equal to the charge of the ion.
• In covalent compounds, electrons are assumed to belong to the more electronegative element.
• The sum of oxidation states in a neutral molecule is 0, while in ions, it equals the ion charge.

Understanding oxidation states helps you predict the behavior of substances in reactions, including which substances might act as oxidizing agents or reducing agents.

Group 14 Elements

Group 14 of the periodic table, also known as the carbon family, includes carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). Each of these elements shares some characteristics but also exhibits key differences:

• They all have four electrons in their outer shell, which makes them versatile in forming various chemical bonds.
• Carbon is non-metal, silicon and germanium are metalloids, while tin and lead are metals.
• Their oxidation states can vary, typically from -4 to +4, reflecting their ability to form different types of compounds.

Silicon and germanium are known for forming semiconductors, crucial in electronics. Tin and lead, on the other hand, are often used in alloys and batteries. These oxidation state variations and applications illustrate the chemical complexity and practical versatility of Group 14 elements.

Chemical Compounds

Chemical compounds are substances composed of two or more elements chemically bonded together. The nature of these bonds can greatly affect the properties of the compound:

• Covalent compounds result from electrons being shared between atoms, exemplified by water (H₂O).
• Ionic compounds are formed by the transfer of electrons from one atom to another, like in sodium chloride (NaCl).
• Each compound has a chemical formula representing the ratio of each element.

In dealing with compounds like silane (SiH4) and germanium dichloride (GeCl2), recognizing these bonds helps in understanding their characteristics. The former relies on covalent bonds whereas the latter involves bonds with more ionic character. This understanding is pivotal in predicting the behavior of compounds in reactions and designing new materials.

Inorganic Chemistry

Inorganic chemistry involves the study of inorganic substances, which are compounds not covered by organic chemistry, typically not containing carbon-carbon (C-C) bonds.

• This field covers a wide array of substances, including metals, minerals, and organometallic compounds, operating outside the traditional organic realm.
• The focus often lies on synthesis, structure, reactivity, and the properties of inorganic materials.
• Elements from across the periodic table, particularly metals, and their compounds, are central to this branch of chemistry.

A good illustration is the compounds formed by Group 14 elements, such as tin dioxide (SnO₂) and lead(IV) nitrate (Pb(NO₃)₄). Mastery in inorganic chemistry allows chemists to create materials with specific properties, crucial in industries ranging from catalysis to materials science.