Question

Using the periodic table to guide you, predict the chemical formula and name of the compound formed by the following elements: (a) Ga and F, (b) Li and H, (c) Al and I, \((\mathbf{d}) \mathrm{K}\) and S.

Short answer

The chemical formulas and names of the compounds formed by the given pairs of elements are: (a) GaF3, Gallium(III) fluoride; (b) LiH, Lithium hydride; (c) AlI3, Aluminum(III) iodide; (d) K2S, Potassium sulfide.

Step-by-step solution

(a) Ga (Gallium) and F (Fluorine)

Using the periodic table, we can find that Ga is in group 13, which means it typically forms a +3 charge when it forms ions. Fluorine is in group 17, which means it typically forms a -1 charge when it forms ions. When the two elements combine to form a compound, they need to balance their charges so that the compound has a neutral charge. In this case, we need 3 F atoms to balance the charge of one Ga atom. So, the chemical formula is GaF3. The name of the compound is Gallium(III) fluoride.

(b) Li (Lithium) and H (Hydrogen)

Using the periodic table, we can find that Li is in group 1, which means it typically forms a +1 charge when it forms ions. Hydrogen is also in group 1 and forms a -1 charge when it forms ions (especially as a hydride). Since both elements have charges of the same magnitude but opposite sign, one Li atom and one H atom are enough to form a neutral compound. So, the chemical formula is LiH. The name of the compound is Lithium hydride.

(c) Al (Aluminum) and I (Iodine)

Using the periodic table, we can find that Al is in group 13, which means it typically forms a +3 charge when it forms ions. Iodine is in group 17, which means it typically forms a -1 charge when it forms ions. To balance the charges and form a neutral compound, we need 3 I atoms for each Al atom. So, the chemical formula is AlI3. The name of the compound is Aluminum(III) iodide.

(d) K (Potassium) and S (Sulfur)

Using the periodic table, we can find that K is in group 1, which means it typically forms a +1 charge when it forms ions. Sulfur is in group 16, which means it typically forms a -2 charge when it forms ions. To balance the charges, we need 2 K atoms for each S atom. So, the chemical formula is K2S. The name of the compound is Potassium sulfide.

Key concepts

Periodic Table

The periodic table is a roadmap for understanding chemical behavior. It organizes elements based on their atomic number, electron configuration, and recurring chemical properties.

Elements are grouped into columns called groups or families, with similar chemical properties. For instance:

• Group 1 (alkali metals) has elements like lithium and potassium, usually forming +1 ions.
• Group 17 (halogens) includes fluorine and iodine, typically forming -1 ions.

Being familiar with the periodic table helps predict how elements interact. It is essential for determining oxidation states, the formation of compounds, and the balancing of chemical charges. Understanding the charge tendencies of elements allows for accurate chemical formula predictions.

Ionic Compounds

Ionic compounds result from the combination of ions with opposite charges. These compounds form through a process whereby atoms lose or gain electrons, achieving a full outer shell. This occurs between metals and non-metals.

Here are some key characteristics of ionic compounds:

• They consist of positively charged cations (often metals) and negatively charged anions (often non-metals).
• The charges are balanced to create a neutral compound, meaning the total positive charge equals the total negative charge.

Examples include Gallium fluoride ( ext{GaF}_3), Lithium hydride ( ext{LiH}), and Potassium sulfide ( ext{K}_2 ext{S}). In each case, the metal loses electrons, and the non-metal gains electrons, resulting in stable ionic structures.

Charge Balancing

Charge balancing is crucial in forming neutral ionic compounds. Every ionic compound must have a net charge of zero, meaning the sum of positive and negative charges needs to be equal.

Consider this balancing act when forming compounds:

• Identify the charges of the ions involved.
• Balance the number of cations and anions so that their total charges cancel each other.

For instance, in aluminum iodide ( ext{AlI}_3), aluminum forms a +3 charge, while each iodine forms a -1 charge. Three iodines are needed to balance one aluminum's charge, resulting in a neutral compound. Similarly, potassium ( ext{K}) and sulfur ( ext{S}) form ext{K}_2 ext{S} to balance the charges: two +1 charges from potassium pair with one -2 charge from sulfur.

Chemical Nomenclature

Chemical nomenclature is the systematic method of naming chemical substances. For ionic compounds, the naming process involves both the cation and anion:

• First, name the metal or positive ion (cation).
• Next, name the non-metal or negative ion (anion), changing the ending to '-ide.'

For metals that can form more than one ion (like Gallium or Aluminum), a Roman numeral indicates the charge of the metal ion.

Examples include: - Gallium(III) fluoride ( ext{GaF}_3): Gallium's charge is stated as (III) since it forms a +3 ion. - Lithium hydride ( ext{LiH}): Hydrogen acts as the negative ion here. - Potassium sulfide ( ext{K}_2 ext{S}): Simply names the ions and changes the ending of sulfur to '-ide.' This systematic approach ensures consistency and clarity in communication within the global scientific community.