The atomic number of an element is 16. Predict (i) the number of valence electrons in its atom (ii) its valency (iii) its group number (iv) whether it is a metal or a non-metal (v) the nature of oxide formed by it (vi) the formula of its chloride

Q: The atomic number of an element is 16. Predict (i) the number of valence electrons in its atom (ii) its valency (iii) its group number (iv) whether it is a metal or a non-metal (v) the nature of oxide formed by it (vi) the formula of its chloride

For an element with atomic number 16 (Sulphur, $S$): (i) **Number of valence electrons:** The electronic configuration is $2, 8, 6$. Therefore, it has **6** valence electrons. (ii) **Valency:** It needs 2 electrons to complete its octet ($8 - 6 = 2$). Its valency is **2**. (iii) **Group number:** For elements with more than 2 valence electrons, Group No. = $10 + \text{valence electrons} = 10 + 6 = $ **16**. (iv) **Metal or Non-metal:** Since it has 6 valence electrons and belongs to group 16, it is a **non-metal**. (v) **Nature of oxide:** Non-metals form acidic oxides. As seen in the text (Activity 1.5), sulphur forms oxides like **$SO_2$ and $SO_3$**, which are **acidic** in nature. (vi) **Formula of its chloride:** With a valency of 2 for Sulphur and 1 for Chlorine, the formula is **$SCl_2$**.

Chemical Reactions and Equations

Periodic Properties and Chemical Formulas

Official Answer

For an element with atomic number 16 (Sulphur, $S$ ):

(i) Number of valence electrons: The electronic configuration is $2, 8, 6$ . Therefore, it has 6 valence electrons.

(ii) Valency: It needs 2 electrons to complete its octet ( $8 - 6 = 2$ ). Its valency is 2.

(iii) Group number: For elements with more than 2 valence electrons, Group No. = $10 + \text{valence electrons} = 10 + 6 =$ 16.

(iv) Metal or Non-metal: Since it has 6 valence electrons and belongs to group 16, it is a non-metal.

(v) Nature of oxide: Non-metals form acidic oxides. As seen in the text (Activity 1.5), sulphur forms oxides like $SO_2$ and $SO_3$ , which are acidic in nature.

(vi) Formula of its chloride: With a valency of 2 for Sulphur and 1 for Chlorine, the formula is $SCl_2$ .

SulphurValence electrons 6Valency 2Group 16Non-metalAcidic oxideSCl2

Marking Scheme

1Correct valence electrons and valency (1 mark)
2Correct group number and classification (non-metal) (1 mark)
3Correct nature of oxide and chloride formula (1 mark)

Hint

First write the electronic configuration ( $2, 8, 6$ ) to determine valence electrons and valency.

Quick Oral Answer

The element is Sulphur. It has 6 valence electrons, a valency of 2, belongs to group 16, is a non-metal, forms acidic oxides like $SO_2$ , and its chloride is $SCl_2$ .

Analysis & Explanation

The element is Sulphur. Its position in the periodic table (Group 16) and its 6 valence electrons define its chemical behavior as a non-metal. Non-metals typically gain electrons (valency 2) and form acidic oxides. The text mentions $SO_2$ and $SO_3$ as gaseous products of the decomposition of ferrous sulphate, which are characteristic non-metal oxides.

Common Mistakes

1Confusing valence electrons (6) with valency (2).
2Identifying the element as a metal because it is in a high group number.

Interesting Facts

Sulphur dioxide ( $SO_2$ ), mentioned in the text, has a characteristic smell of burning sulphur and is a major contributor to acid rain because of its acidic nature.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2011?

This question carries 3 marks in the CBSE Class 10 Science 2011 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Periodic Properties and Chemical Formulas" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2011 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.