Question

Out of the three elements P, Q and R having atomic numbers 11, 17 and 19 respectively, which two elements will show similar properties and why? [Foreign 2014]

Answer 1

GiveN :

• There elements are named as P,Q,R having atomic numbers 11, 17 , 19

To FinD :

• Which one will show same properties why ?

SolutioN :

The two elements which will show the same properties are P and R. Because these both the elements belong to 1st group. So, their properties are similar to each other.

• Element P is Sodium
• Element R is Potassium

They both have one electron filled in outer most shell. Potassium is the most reactive metal in the periodic Table. And they both have oxidation state as +1 .

Mass of Sodium is 23 u where as the mass of Potassium is 40 u. Group 1 elements are also called as Alkali Metals. Their oxides are Acidic in nature. Sodium is denoted by Na. Potassium is denoted as K.

Electronic Configuration :

$\bullet \: \sf{Na \: = \: 1s^2 \: 2s^2 \: 2p^6 \: 3s^1} \\ \ \bullet \: \sf{K \: = \: 1s^2 \: 2s^2 \: 2p^6 \: 3s^2 \: 3p^6 \: 3d^1}$

Answer 2

AnsWer :

✴ Given :-

▪ Atomic number of element P = 11

▪ Atomic number of element Q = 17

▪ Atomic number of element R = 19

✴ To Find :-

▪ Which two elwments out of three will show similar properties and why.....

✴ Concept :-

✈ We know that, Elements from same group contain similar physical and chemical properties.

✴ Explanation :-

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• Electron configuration of P

$\sf\:_{11}P=[Ne]3s^1$

Group number : 1

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• Electron configuration of Q

$\sf\:_{17}Q=[Ne]3s^2\:3p^5$

Group number : 10 + 7 = 17

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• Electron configuration of R

$\sf\:_{19}R=[Ar]4s^1$

Group number = 1

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✒ As per electron configuration of P, Q and R it is clear that, P and R will show similar properties...