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Periodic Classification of Elements — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10SciencePeriodic Classification of Elements3 Marks
Question
An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound. Answer the following questions giving reason:
Write the position of P and Q in the Modern Periodic Table and the molecular formula of the compound formed when P reacts with Q.
✓

Answer

Atomic number of element P is 20
electronic configuration = 2, 8, 8, 2
Valence electron = 2
Group-2
Atomic number of element Q is 17
electronic configuration Q = 2, 8, 7
Valence electron = 1
Group-3
When P reacts with Q, it loses the two valence electrons (valency 2). These two valence electrons are accepted by two Q atoms (valency 1). Hence, the formula of the compound formed between P and Q is $PQ_2$.

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