Question

Supply a Stock system name for each of the following binary ionic compounds: (a) ${\mathrm{MnCl}}_2$ (b) ${\mathrm{NiF}}_2$ (c) ${\mathrm{SnBr}}_2$ (d) CrP

Short answer

(a) Manganese(II) chloride, (b) Nickel(II) fluoride, (c) Tin(II) bromide, (d) Chromium(III) phosphide.

Step-by-step solution

Understand the problem

We are given binary ionic compounds, each consisting of a metal and a non-metal. The task is to write the Stock system name, where the metal is specified by its elemental name with its oxidation state in Roman numerals in parentheses.

Ionic compound (a): MnCl2

Manganese forms multiple oxidation states, and in MnCl2, manganese must balance the -2 charge of the two chloride ions, each with a charge of -1. Thus, the oxidation state of manganese here is +2, leading to the name 'Manganese(II) chloride.'

Ionic compound (b): NiF2

Like manganese, nickel can have multiple oxidation states. To determine nickel's oxidation state in NiF2, we note that fluorine is always -1 in ionic compounds. The two fluorides total a -2 charge, so nickel must be in the +2 state to balance this. Hence, the name is 'Nickel(II) fluoride.'

Ionic compound (c): SnBr2

Tin can show different oxidation numbers, commonly +2 and +4. In SnBr2, each bromide has a -1 charge, summing to -2. Therefore, tin must be at +2 to achieve neutrality. Thus, the name is 'Tin(II) bromide.'

Ionic compound (d): CrP

Chromium has several oxidation states, but in CrP, phosphorus is in a -3 state, meaning chromium is in the +3 state for the formula to be neutral. So, this is called 'Chromium(III) phosphide.'

Key concepts

Binary Ionic Compounds

Binary ionic compounds are made up of two elements: one is a metal, and the other is a non-metal. These compounds form through the transfer of electrons from the metal to the non-metal. This transfer results in a positive ion (cation) and a negative ion (anion), which attract each other due to opposite charges. Using the Stock system, we can name these compounds by specifying the cation with its oxidation state, written in Roman numerals. This helps clarify which oxidation state the metal is in, especially for transition metals that often have multiple states. For example, in MnCl_2, manganese is named with an oxidation state of +2.

Oxidation States

Oxidation states indicate the degree of oxidation of an element in a compound. They reflect the number of electrons lost or gained by an atom in a substance. To determine the oxidation state in a binary ionic compound, we balance the total positive and negative charges. When using the Stock system, knowing the oxidation state is crucial because many metals can exist in multiple oxidation states.

• For MnCl_2, manganese has a +2 oxidation state because it balances the two chloride ions, each with a -1 charge.
• In NiF_2, nickel's oxidation state is also +2, balancing two -1 fluoride ions.
• SnBr_2 has tin in a +2 oxidation state, aligning with two bromide ions at -1 each.
• CrP assigns chromium a +3 oxidation state, given phosphorus typically has a -3 state.

Manganese Chloride

Manganese chloride is a binary ionic compound with the formula MnCl_2. This compound comprises manganese and chloride ions. Manganese has various oxidation states, but when it forms manganese chloride, it exhibits a +2 oxidation state. This is necessary to neutralize the -2 charge from the two chloride ions. Therefore, the Stock system name for MnCl_2 is Manganese(II) chloride. This naming clarifies that manganese is in a +2 oxidation state, distinguishing it from other potential compounds where manganese might have different oxidation levels.

Nickel Fluoride

Nickel fluoride, with the chemical formula NiF_2, consists of nickel and fluoride ions. Nickel is a transition metal capable of multiple oxidation states, but in nickel fluoride, its oxidation state must be +2. This is because the two fluoride ions carry a total charge of -2, with each fluoride contributing -1. To ensure charge neutrality, nickel must counterbalance with a charge of +2. Therefore, the correct Stock name for NiF_2 is Nickel(II) fluoride. This precise naming helps avoid confusion with other nickel compounds that may have a different oxidation state.

Tin Bromide

Tin bromide is the binary ionic compound with the formula SnBr_2. Tin, the metal, pairs with bromide ions in this structure. Tin can have different oxidation states, particularly +2 and +4. In SnBr_2, each bromide ion carries a -1 charge. Consequently, with two bromide ions, the total negative charge is -2. Hence, tin must be in a +2 oxidation state to neutralize these charges. The Stock system name Tin(II) bromide indicates this oxidation level, distinguishing it clearly from other potential tin compounds with different charged states.

Chromium Phosphide

Chromium phosphide, represented as CrP, is a combination of chromium and phosphorus ions. Phosphorus commonly has a -3 charge as an ion. To achieve a neutral compound, chromium must balance this with a +3 charge in CrP. Therefore, the Stock system name for this compound is Chromium(III) phosphide, highlighting chromium's +3 oxidation state. This notation is imperative given chromium's ability to adopt different oxidation numbers, ensuring the clarity and accuracy of chemical communications involving chromium compounds.