Question

An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is:

• A. 11
• B. 17
• C. 18
• D. 20

Answer 1

The correct option is B

17

Explanation of the correct option:

(b):

Electronic configuration of atomic number 19 = 2, 8, 8, 1

• From the electronic configuration, it is obvious that the element will lose an electron to gain stability to achieve an octet of electrons.
• So this element can chemically combine with an element that will accept that electron lost by the element with atomic number 19.
• The tendency of an element that will accept this one electron can be predicted from its electronic configuration.

For atomic number 17, electronic configuration= 2, 8, 7.

• It needs one electron to complete its octet.
• Therefore, it will prefer to chemically combine with element with atomic number 19.

Explanation of the incorrect options:

(a) For atomic number 11, electronic configuration= 2, 8, 1

• It tends to lose an electron from its valence shell to complete its octet. Therefore, it cannot accept one electron and will not chemically combine.

(c) For atomic number 18, electronic configuration= 2, 8, 8

• It does not tend to combine with other elements because it has a complete octet of electrons and is therefore inert and will not combine chemically with the element in question.

(d) For atomic number 20, electronic configuration= 2, 8, 8, 2

• It will lose 2 electrons and will not combine with the given element because it cannot accept electrons lost by the said element.

Hence, option (b) is correct.