Question

Predict the formula and name of a binary compound formed from the following elements: (a) \(\mathrm{Na}\) and \(\mathrm{H}\), (d) \(\mathrm{Al}\) and \(\mathrm{F},(\mathrm{e}) \mathrm{F}\) and \(\mathrm{O}\) (b) \(\mathrm{B}\) and \(\mathrm{O},(\mathrm{c}) \mathrm{Na}\) and \(\mathrm{S},\) (f) \(\mathrm{Sr}\) and \(\mathrm{Cl}\).

Short answer

(a) \(\mathrm{NaH}\), Sodium hydride (b) \(\mathrm{B_2O_3}\), Boron trioxide (c) \(\mathrm{Na_2S}\), Sodium sulfide (d) \(\mathrm{AlF_3}\), Aluminum fluoride (e) \(\mathrm{OF_2}\), Difluorine monoxide (f) \(\mathrm{SrCl_2}\), Strontium chloride

Step-by-step solution

Identify Element Charges

Binary compounds are composed of two different elements. To determine the time-tested formula, we first need to understand the oxidation states or charges of each element involved. This can typically be assessed using the periodic table. Elements in group 1, like \(\mathrm{Na}\), form ions with a +1 charge. Elements in group 2, like \(\mathrm{Sr}\), form ions with a +2 charge. \(\mathrm{H}\) typically has a -1 oxidation state in metal hydrides. Group 16 elements like \(\mathrm{O}\) and \(\mathrm{S}\) generally have a -2 charge in compounds. Group 17 elements like \(\mathrm{F}\) and \(\mathrm{Cl}\) usually have a -1 charge.

Combine the Elements to Form Compounds

Using the oxidation states, we combine the elements in specific ratios to neutralize charge, forming compounds:(a) \(\mathrm{Na}^+\) and \(\mathrm{H}^-\) combine to form \(\mathrm{NaH}\).(b) Two \(\mathrm{B}^{3+}\) and three \(\mathrm{O}^{2-}\) would make \(\mathrm{B_2O_3}\).(c) Two \(\mathrm{Na}^+\) and one \(\mathrm{S}^{2-}\) result in \(\mathrm{Na_2S}\).(d) One \(\mathrm{Al}^{3+}\) and three \(\mathrm{F}^-\) form \(\mathrm{AlF_3}\).(e) Three \(\mathrm{F}^-\) and two \(\mathrm{O}^{2-}\) form \(\mathrm{OF_2}\).(f) One \(\mathrm{Sr}^{2+}\) and two \(\mathrm{Cl}^-\) produce \(\mathrm{SrCl_2}\).

Name the Compounds

After forming the compounds, we name them. Since they are binary ionic compounds, the cation (positive ion) is named first, followed by the anion (negative ion), modifying the anion's name to end with '-ide.'(a) Sodium hydride (\(\mathrm{NaH}\))(b) Boron trioxide (\(\mathrm{B_2O_3}\))(c) Sodium sulfide (\(\mathrm{Na_2S}\))(d) Aluminum fluoride (\(\mathrm{AlF_3}\))(e) Difluorine monoxide (\(\mathrm{OF_2}\))(f) Strontium chloride (\(\mathrm{SrCl_2}\))

Key concepts

Oxidation States

Understanding oxidation states is crucial when dealing with binary compounds. The oxidation state indicates the degree of oxidation or loss of electrons in an element. This concept often helps in determining how elements combine in a compound. For example, the oxidation state of sodium (\( \mathrm{Na}^+ \)) is +1 because it tends to lose one electron. Hydrogen (\( \mathrm{H}^- \)) can have an oxidation state of -1, especially in metal hydrides. Recognizing these states allows chemists to predict how elements will interact. Referencing the periodic table is key, as elements often follow predictable patterns according to their group. Group 1 elements have a +1 oxidation state, group 2 elements are typically +2, and so on. Meanwhile, elements like oxygen in group 16 usually exhibit a -2 oxidation state.

Ionic Charges

Ionic charges play a vital role in forming binary compounds. When elements combine, they either lose or gain electrons to achieve stable electron configurations similar to noble gases. This transfer results in ions with positive or negative charges. Cations are positively charged ions, while anions carry a negative charge. They combine in specific ratios to neutralize these charges.

• Sodium (\( \mathrm{Na} \)) typically forms a +1 ion (cation).
• Chlorine (\( \mathrm{Cl} \)) forms a -1 ion (anion).

Using the charges, we determine how many of each ion are needed to balance the compound. For instance, in sodium sulfide (\( \mathrm{Na_2S} \)), two sodium ions (\( \mathrm{Na}^+ \)) balance one \( \mathrm{S}^{2-} \) ion.

Compound Naming

Naming binary compounds is straightforward if you understand the structure. You begin with the name of the cation followed by the anion. For ionic binary compounds, like those with metal and non-metal components, you change the ending of the anion’s name to '-ide.' This suffix change is standard and makes it easier to identify the type of compound:

• NaH is named sodium hydride.
• Aluminum fluoride is \( \mathrm{AlF_3} \).

These names reflect the elements involved and their ionic bonds. Therefore, by examining the composition of the compound, its name can be effectively derived.

Periodic Table Groups

The periodic table is more than a list of elements; it provides valuable insight into the behavior of elements in compounds. Elements are grouped based on similar properties and increasing atomic numbers. Understanding these groupings helps in predicting ionic charges and bonding patterns:

• Group 1: Alkali metals like sodium (\( \mathrm{Na} \)), which tend to form +1 ions.
• Group 2: Alkaline earth metals like strontium (\( \mathrm{Sr} \)), typically forming +2 ions.
• Group 17: Halogens such as fluorine (\( \mathrm{F} \)), often forming -1 ions.

By familiarizing yourself with each group's typical ion charge, you can predict how different elements might combine to form stable binary compounds.