Chemistry
The electronic configuration of the element which has the largest atomic size is:
- 2, 8, 5
- 2, 8, 1
- 2, 8, 7
- 2, 1
Periodic Table
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Answer
2, 8, 1
Reason — Atomic radius increases down a group because each successive period adds a new electron shell, and it decreases from left to right across a period owing to increasing nuclear charge.
- Configurations 2, 1 and 2, 8, 1 belong to Group 1.
- Element with electronic configuration (2, 8, 1) is one period below lithium, so it possesses an additional electron shell and therefore a larger atomic radius.
- The remaining configurations (2, 8, 5) and (2, 8, 7) lie further to the right in Period 3, where atomic size is smaller.
Hence, the element with configuration 2, 8, 1 has the largest atomic size among the choices given.
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Related Questions
State the element with the lowest electron affinity from the elements whose electronic configurations are below:
- 2, 8, 8
- 2, 7
- 2, 8, 6
- 2, 8, 7
Non-metallic elements have:
- Large atomic size
- Low electron affinity
- High ionisation potential
- Greater tendency to lose electrons.
Rewrite the incorrect statements only by rectifying the incorrect word/s in the statement.
(a) Periodic table is based on the fundamental property atomic weight.
(b) Elements in the periodic table are arranged in seven horizontal rows called 'groups', which ends with an element having one electron in outermost shell.
(c) Period numbers i.e., 1, 2, 3 signifies the no. of electron shells of an element e.g. period 3 element 'Mg' has 2 shells.
(d) Across a period from left to right the no. of electron shells increases by one & the valence electron remains same.
(e) Group numbers i.e., 1, 2, 3 signifies the number of electron shells of an element.
(f) Down a sub-group, the valence electrons & the number of electron shells remains same.
Correct the order of elements in period 1 to 3 of the periodic table & state their correct electronic configurations.
Period Group 1 Group 2 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18 (O) 1 H He 2 Li [2,1] C O N B Be F Ne 3 Na Al Si Mg S Cl P Ar 4 K Ca Br Kr