2 marksShort AnswerSection A

An element has atomic number 13. (a) What is the group and period number to which this element belongs? (b) Is this element a metal or a non-metal? Justify your answer.

Q: An element has atomic number 13. (a) What is the group and period number to which this element belongs? (b) Is this element a metal or a non-metal? Justify your answer.

(a) The element with atomic number $13$ belongs to **Group 13** and **Period 3**. (b) This element is a **metal** (Aluminium). **Justification:** Its electronic configuration is $2, 8, 3$. Since it has $3$ valence electrons, it can easily lose these $3$ electrons to achieve a stable octet configuration, forming a tripositive cation ($\text{Al}^{3+}$). Elements that lose electrons to form positive ions are electropositive and are classified as metals. Furthermore, as shown in the NCERT text, Aluminium ($\text{Al}$) exhibits metallic properties such as high thermal conductivity, malleability, and ductility, and it forms an amphoteric oxide ($\text{Al}_2\text{O}_3$).

Metals and Non-metals

Properties of Aluminium

Official Answer

(a) The element with atomic number $13$ belongs to Group 13 and Period 3.

(b) This element is a metal (Aluminium).

Justification: Its electronic configuration is $2, 8, 3$ . Since it has $3$ valence electrons, it can easily lose these $3$ electrons to achieve a stable octet configuration, forming a tripositive cation ( $\text{Al}^{3+}$ ). Elements that lose electrons to form positive ions are electropositive and are classified as metals. Furthermore, as shown in the NCERT text, Aluminium ( $\text{Al}$ ) exhibits metallic properties such as high thermal conductivity, malleability, and ductility, and it forms an amphoteric oxide ( $\text{Al}_2\text{O}_3$ ).

Group 13Period 3metalAluminiumelectronic configuration2, 8, 3lose electronselectropositivecation

Marking Scheme

11 mark
21 mark

Hint

Write the electronic configuration of the element with atomic number 13. The number of shells gives the period, and the number of valence electrons determines the group and metallic character.

Quick Oral Answer

The element is Aluminium. It belongs to Group 13 and Period 3. It is a metal because it has 3 valence electrons which it can easily lose to form a positive ion.

Analysis & Explanation

Aluminium (atomic number 13) is a well-known metal. In the NCERT text, it is used in several activities demonstrating metallic properties: Activity 3.1 (metallic lustre), Activity 3.5 (good conductor of heat), and Section 3.2.1 (forming amphoteric oxide $\text{Al}_2\text{O}_3$ ). Chemically, metals are electropositive elements that lose valence electrons to form cations, which perfectly justifies why Aluminium is classified as a metal.

Common Mistakes

1Writing the group number as 3 instead of 13.
2Failing to justify the metallic character using the electronic configuration or electropositive nature.

Interesting Facts

Aluminium is the most abundant metal in the Earth's crust, and its oxide, $\text{Al}_2\text{O}_3$ , is amphoteric, meaning it reacts with both acids and bases to form salt and water.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2012?

This question carries 2 marks in the CBSE Class 10 Science 2012 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Properties of Aluminium" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2012 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2012 paper.