Question

Out of three elements PQR having atomic number 17 11 19 respectively which two element show similar properties why

Answer 1

p = 17(2,8,7)=chlorine
q= 11(2,8,1)=sodium
r= 19 (2,8,8,1) = potassium
r , q are similar because they are metal

Answer 2

Elements Q and R having atomic number 11 and 19 respectively show similar chemical properties.

Explanation:

Elements present in same group have same number of valence electrons and valence electrons determine the chemical properties.

Atomic number of Chlorine is 17, it means that it has 17 protons and 17 electrons. $P:17:1s^22s^22p^63s^23p^5$

Atomic number of sodium is 11, it means that it has 11 protons and 11 electrons. $Q:11:1s^22s^22p^63s^1$

Atomic number of potassium is 19, it means that it has 19 protons and 19 electrons. $R:19:1s^22s^22p^63s^23p^64s^1$

Sodium and Potassium both contain 1 valence electron and hence they show similar properties.

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