Question

An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.)
N(7) F(9) P(15) Ar(18)

NCERT Class X
Science - Science

Chapter_Periodic Classification of Elements

Answer 1

Given:

Electronic configuration of an atom = 2, 8, 7

To find:

Atomic number of the element =?

Chemical similarity = ?

Solution:

• As the electronic configuration of the given atom is 2,8,7 it is inferred that the atomic number of element is 17 (2+8+7).
• Thus element with atomic number 17 is Chlorine.
• Among the options given which includes Nitrogen, Fluorine, Phosphorus and Argon, chlorine is chemically similar to fluorine.
• It is because chlorine and Fluorine belongs to same group 17 and they are called as halogens.
• Other elements such as Nitrogen, Phosphorus and Argon are not halogens.

Learn more about such concept

Given below are some elements of the modern periodic table. Atomic number of the element is given in the parentheses : A(4), B(9), C(14), D(19), E(20) (a) Select the element that has one electron in the outermost shell, Also write the electronic configuration of this element. (b) Which two elements among these belong to the same group ? Give reason for your answer. (c) Which two elements amongst these belong to the same period ? Which one of the two has bigger atomic radius?

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Answer 2

Answer:

a) answer is 17 and b answer is F(9)

Explanation:

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