A) seven periods: three short and four long
B) nine periods: six short and three long
C) eighteen periods: ten short and eight long
D) nine periods from zero to VIII
Correct Answer: A
Solution :
The long form of periodic table consists of seven periods. The number of elements in a period and the type of orbitals being filled up is given in the table.| Period | No. of the energy level being filled | Orbitals being filled | No. of electrons or elements in the period |
| 1. | \[n=1\] | \[1s\] | 2 (very short period) |
| 2. | \[n=2\] | \[2s,\,\,2p\] | 8 (short period) |
| 3. | \[n=3\] | \[3s,\,\,3p\] | 8 (short period) |
| 4. | \[n=4\] | \[4s,\,\,3d,\,\,4p\] | 18 (long period) |
| 5. | \[n=5\] | \[5s,\,\,4d,\,\,5p\] | 18 (long period) |
| 6. | \[n=6\] | \[6s,\,\,4f,\,\,5d,\,\,6p\] | 32 (very long period) |
| 7. | \[n=7\] | \[7s,\,\,5f,\,\,6d,\,\,7p\] | 29 (incomplete period) |
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