Magnesium has a valency of two, and the nitrate ion (NO₃⁻) has a valency of one. These values represent their respective combining capacities in chemical reactions.
Understanding Valency
Valency is a fundamental concept in chemistry that describes the combining capacity of an element or ion. It indicates the number of chemical bonds an atom or ion can form. This property is crucial for understanding how atoms and ions combine to form stable chemical compounds, determining their stoichiometry and molecular formulas.
Valency of Magnesium (Mg)
Magnesium (Mg) is an alkaline earth metal, located in Group 2 of the periodic table. Elements in this group typically have two valence electrons in their outermost shell. To achieve a stable electron configuration, similar to that of a noble gas, magnesium readily loses these two valence electrons.
- When magnesium loses two electrons, it forms a positively charged ion, Mg²⁺.
- The magnitude of this charge determines its valency.
- Therefore, the valency of magnesium is two, reflecting its tendency to form two chemical bonds. This fact is consistently observed in chemical reactions and compounds involving magnesium.
Examples of Magnesium Compounds:
- Magnesium chloride (MgCl₂): One magnesium atom combines with two chlorine atoms (each with valency 1).
- Magnesium oxide (MgO): One magnesium atom combines with one oxygen atom (with valency 2).
Valency of Nitrate (NO₃⁻)
Nitrate is a polyatomic ion, meaning it is a group of atoms covalently bonded together that carries an overall electric charge. The chemical formula for the nitrate ion is NO₃⁻.
- The nitrate ion has a net charge of -1.
- For polyatomic ions, their valency is equal to the absolute value of their overall charge.
- Consequently, the valency of the nitrate ion is one, indicating it can form one chemical bond to achieve electrical neutrality in a compound.
Examples of Nitrate Compounds:
- Sodium nitrate (NaNO₃): One sodium ion (Na⁺, valency 1) combines with one nitrate ion (NO₃⁻, valency 1).
- Calcium nitrate (Ca(NO₃)₂): One calcium ion (Ca²⁺, valency 2) combines with two nitrate ions (NO₃⁻, each with valency 1) to balance the charge.
Summary of Valencies
| Species | Chemical Formula | Valency | Explanation |
|---|---|---|---|
| Magnesium | Mg | 2 | Loses two valence electrons to form Mg²⁺ ion. |
| Nitrate | NO₃⁻ | 1 | A polyatomic ion with an overall charge of -1. |
Understanding these valencies is essential for correctly predicting the formulas of compounds formed between magnesium and nitrate, such as magnesium nitrate, which has the formula Mg(NO₃)₂.
