The chemical formula for lithium phosphide is Li3P. Which best describes this ionic compound?
The Correct Answer and Explanation is:
Correct Answer:
Lithium phosphide is an ionic compound made of three lithium ions and one phosphide ion.
Explanation:
Lithium phosphide, with the chemical formula Li₃P, is a classic example of an ionic compound. It consists of positively charged lithium ions (Li⁺) and negatively charged phosphide ions (P³⁻). In ionic compounds, atoms transfer electrons to achieve stable electron configurations, usually resembling that of noble gases.
Lithium belongs to Group 1 of the periodic table, known as the alkali metals. These elements have one electron in their outermost shell, which they readily lose to form Li⁺ ions. By losing this electron, lithium attains a stable electronic structure similar to helium, a noble gas.
Phosphorus, on the other hand, belongs to Group 15 of the periodic table and has five electrons in its outer shell. It needs three more electrons to complete its octet. When phosphorus gains three electrons, it forms the P³⁻ ion.
To balance the charges in lithium phosphide, three Li⁺ ions (each with a +1 charge) combine with one P³⁻ ion (with a -3 charge). The overall positive and negative charges cancel each other, resulting in a neutral compound, Li₃P.
This compound forms a crystalline structure held together by strong electrostatic forces between the oppositely charged ions, which is typical for ionic substances. Such compounds tend to have high melting and boiling points due to these strong attractions. They are also generally solid at room temperature and can conduct electricity when molten or dissolved in water, though lithium phosphide reacts with water, releasing phosphine gas.
In summary, lithium phosphide is an ionic compound composed of three lithium ions and one phosphide ion, combining to form a stable, electrically neutral compound with characteristic ionic properties.
