Understanding Basic Oxides and Atomic Number

Oxides are chemical compounds that contain at least one oxygen atom and one other element in their chemical formula. Based on their chemical properties, oxides can be classified as acidic, basic, amphoteric, or neutral.

Basic oxides are typically formed by metals, especially alkali metals and alkaline earth metals. These oxides react with acids to form salt and water, and many soluble basic oxides (like those of alkali metals and heavier alkaline earth metals) dissolve in water to form basic solutions (metal hydroxides).

Acidic oxides are typically formed by non-metals. These oxides react with bases to form salt and water, and many dissolve in water to form acidic solutions (oxyacids).

Amphoteric oxides show properties of both acidic and basic oxides. They can react with both acids and bases.

Neutral oxides do not react with acids or bases.

Analyzing Atomic Numbers for Basic Oxide Formation

The question asks which atomic number corresponds to an element that will form a basic oxide. We need to identify the element associated with each given atomic number and determine if it is a metal or a non-metal, as this generally indicates the nature of its oxide.

• Atomic Number 7: This is Nitrogen (N). Nitrogen is a non-metal located in Group 15 of the periodic table. Non-metals typically form acidic oxides. Oxides of nitrogen, like \( \text{N}_2\text{O}_5 \), are acidic.
• Atomic Number 20: This is Calcium (Ca). Calcium is an alkaline earth metal located in Group 2 of the periodic table. Metals, especially those in Group 1 and 2, typically form basic oxides. Calcium oxide (\( \text{CaO} \)) is a well-known basic oxide.
• Atomic Number 17: This is Chlorine (Cl). Chlorine is a halogen, which is a non-metal, located in Group 17 of the periodic table. Non-metals typically form acidic oxides. Oxides of chlorine, like \( \text{Cl}_2\text{O}_7 \), are acidic.
• Atomic Number 6: This is Carbon (C). Carbon is a non-metal located in Group 14 of the periodic table. Non-metals typically form acidic or neutral oxides. Carbon dioxide (\( \text{CO}_2 \)) is acidic, and carbon monoxide (\( \text{CO} \)) is neutral.

Based on this analysis, the element with atomic number 20, Calcium, is a metal that forms a basic oxide.

Therefore, an element with an atomic number of 20 will form a basic oxide.

Revision Table: Basic Oxides and Atomic Number

Additional Information: Classifying Oxides

The chemical nature of an element's oxide is strongly correlated with the element's position in the periodic table and its electronegativity. Elements with low electronegativity (metals) tend to form basic oxides, while elements with high electronegativity (non-metals) tend to form acidic oxides. Elements with intermediate electronegativity can form amphoteric oxides.

Examples of different oxide types:

• Basic Oxides: \( \text{Na}_2\text{O} \) (Sodium oxide), \( \text{K}_2\text{O} \) (Potassium oxide), \( \text{CaO} \) (Calcium oxide), \( \text{MgO} \) (Magnesium oxide).
• Acidic Oxides: \( \text{SO}_2 \) (Sulfur dioxide), \( \text{SO}_3 \) (Sulfur trioxide), \( \text{CO}_2 \) (Carbon dioxide), \( \text{P}_4\text{O}_{10} \) (Phosphorus decoxide), \( \text{N}_2\text{O}_5 \) (Dinitrogen pentoxide).
• Amphoteric Oxides: \( \text{Al}_2\text{O}_3 \) (Aluminum oxide), \( \text{ZnO} \) (Zinc oxide), \( \text{PbO} \) (Lead(II) oxide).
• Neutral Oxides: \( \text{CO} \) (Carbon monoxide), \( \text{NO} \) (Nitric oxide), \( \text{N}_2\text{O} \) (Nitrous oxide).

Understanding the relationship between an element's metallic character and the properties of its oxide is fundamental to inorganic chemistry.