Green chemistry methods, which use nontoxic chemicals, are replacing elemental c

Question

Green chemistry methods, which use nontoxic
chemicals, are replacing elemental chlorine for the
bleaching of paper pulp. Chlorine causes problems
because it is a strong oxidizing agent that reacts with organic
compounds to form toxic by-products such as furan and dioxins.
(a) Write the electron configuration of a chlorine atom in its
ground state. How many unpaired electrons are present in the
atom? Write the electron configuration you expect a chloride ion
to have. The electron configuration of the chloride ion is identical
to that of a neutral atom of what other element?
(b) When a chlorine atom is excited by heat or light, one of its
valence electrons may be promoted to a higher energy level. Predict
the most likely electron configuration for the lowest possible
excited state for an excited chlorine atom.
(c) Estimate the wavelength (in nm) of the energy that needs to be
absorbed for the electron to reach the excited state in part (b). To
make this estimate, use Eq
      En=-Z^2hR/n^2
and take the effective nuclear charge as 6
(d) What is the value of the energy required in part (c) in kilojoules
per mole and electronvolts?
(e) The proportion of 37Cl in a typical sample is 75.77%, with the
remainder being 35Cl. What would the molar mass of a sample of
chlorine atoms be if the proportion of 37Cl were reduced to half
its current value? The mass of an atom of 35Cl is (5.807 × 10^-23) g
and that of an atom of 37Cl is
(6.139 × 10^-23) g.

Explanation / Answer

a)   Atomic number of Chlorine = 17

Electron configuration of chlorine atom in its ground state = 1s2 2s2 2p6 3s2 3p5

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No of unpaired electrons are present in the Chlorine atom = 1

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Electron configuration of a chloride ion Cl- = 1s2 2s2 2p6 3s2 3p6

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Electron configuration of chloride ion is identical to Argon.

Atomic no of Argon = 18

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