Final answer:
The noble gas notation for chlorine (Cl) is [Ne]3s²3p⁵ and for yttrium (Y) is [Kr]5s²4d¹. This notation represents the core electrons with the symbol of the nearest preceding noble gas and the valence electron configuration thereafter.
Step-by-step explanation:
Noble Gas Notation for Chlorine (Cl) and Yttrium (Y)
To find the electron configuration of an element in noble-gas notation, you locate the nearest noble gas that comes before the element in the periodic table. You use the noble gas to represent the core electrons and then add the remaining valence electron configuration.
For chlorine (Cl), which has 17 electrons, the nearest noble gas is neon (Ne), which has 10 electrons. Therefore, the noble-gas notation for chlorine is [Ne]3s²3p⁵.
For yttrium (Y), with 39 electrons, the nearest noble gas is krypton (Kr), which has 36 electrons. The remaining 3 electrons go into the 5s and 4d orbitals. Therefore, the noble-gas notation for yttrium is [Kr]5s²4d¹.