Question

Without referring to Table 2.6 but using the periodic table, write chemical formulas for the simplest hydrogen compounds of (a) carbon, (b) nitrogen, (c) tellurium, and (d) iodine.

Short answer

The simplest hydrogen compounds are CH4 (methane) for carbon, NH3 (ammonia) for nitrogen, H2Te for tellurium, and HI (hydrogen iodide) for iodine.

Step-by-step solution

Understand the Concept

The simplest hydrogen compounds of an element are called hydrides. Generally, for most nonmetals, the simplest hydrogen compound is formed by bonding sufficient hydrogen atoms to fulfill the octet rule for the nonmetal. The number of hydrogen atoms needed corresponds to the number of electrons required to complete the octet (8 electrons in total for most elements, except hydrogen itself which requires 2 electrons to complete its valence shell).

Determine Valencies

To determine the simplest hydrogen compounds, we need to look at the valencies of each element. Carbon has 4 valence electrons and requires 4 more to complete its octet. Nitrogen has 5 valence electrons and needs 3 more hydrogens. Tellurium is in the same group as oxygen and sulfur, with 6 valence electrons, needing 2 additional hydrogens. Iodine, being a halogen, has 7 valence electrons and requires only 1 hydrogen atom to form the simplest compound.

Write the Chemical Formulas

Using the valencies determined in Step 2, we can now write the chemical formulas for each element's simplest hydrogen compound. For carbon, it's methane with the formula CH4. For nitrogen, it's ammonia with the formula NH3. For tellurium, the hydride would be H2Te. And for iodine, it would be hydrogen iodide with the formula HI.

Key concepts

Chemical Formulas

Chemical formulas represent the types and numbers of atoms in a substance. Using the periodic table, we can determine these formulas by looking at the valence electrons of each element. For example, carbon, positioned in group 4, has four valence electrons which means it can bond with four hydrogen atoms to form methane, represented by the chemical formula CH₄.

Chemical formulas are not just symbols; they hold critical information about the substance. Methane's formula indicates that one carbon atom is bonded to four hydrogen atoms. This visual representation simplifies understanding the makeup of compounds and is fundamental in the study of chemistry.

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom that can participate in chemical bonding. For instance, nitrogen has five valence electrons and needs three more to achieve a stable electron configuration. Identifying valence electrons helps us predict how elements will react and what kind of compounds they will form. In the periodic table, elements in the same group typically have the same number of valence electrons, which is key to understanding their chemical behavior.

Octet Rule

The octet rule is a chemical rule of thumb that states atoms tend to bond in such a way that they have eight electrons in their valence shell, giving them the same electron configuration as a noble gas. Hydrogen is an exception, requiring just two electrons. This rule helps explain the formation of the simplest hydrogen compounds. For example, tellurium needs two additional electrons to complete its octet, leading to the chemical formula H₂Te. The octet rule is essential in predicting the bonding patterns of elements.

Chemical Bonding

Covalent Bonding

Chemical bonding involves the sharing or transfer of valence electrons between atoms to achieve stability. In hydrogen compounds like methane (CH₄) or ammonia (NH₃), the bonds are covalent, meaning the atoms share electrons to fulfill the octet rule. Understanding these interactions allows us to predict molecular structures and the properties of substances.

Ionic Bonding

While our focus here is on covalent bonding with hydrogen, ionic bonding is another type of chemical bond where electrons are transferred from one atom to another, creating oppositely charged ions that attract each other.

Periodic Table

The periodic table is a tabular arrangement of the chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties. Elements are placed in groups that share common characteristics, which is useful in predicting their behavior during chemical reactions. For example, iodine is part of the halogens group, which generally form compounds by gaining one electron. Hence, the simplest hydrogen compound for iodine is hydrogen iodide or HI, where iodine has gained one electron from hydrogen.