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Chemical Processes Answers

1. (c) The ionic bond was first described by with each of three hydrogen atoms; both atoms can
Walther Kossel. According to him, the maximum complete their shell. After sharing electrons with
number of electrons that can be present in each hydrogen, nitrogen now has total eight electrons
shell should be two in the first shell, eight in the (octet) in its outer shell, whereas each hydrogen
second shell, eight or eighteen in the third shell and atom has two electrons.
so on. The molecule that has the full outer shell will
express the greatest stability, e.g. noble gases such 3.(c) The region in space where an electron is likely
as N 2, O 2, Cl 2, etc. to be found is called an orbital. There are different
kinds of orbitals with different sizes and shapes. The
orbital at the lowest energy level is defined as a 1s
orbital. It is a sphere with its center at the nucleus
of the atom. The next higher energy level is called a
2s orbital. It is larger than a 1s orbital. Since it has a
higher energy level, it has lower stability compared
to a 1s orbital. This is because the average distance
between the nucleus and electrons in 2s orbital is
greater than in 1s orbital. The next three orbitals
For example, in the formation of lithium fluoride, a are of equal energy, known as 2p orbitals. They are
lithium atom has only one electron in its outer or dumbbell-shaped. They are further differentiated
valence shell; the loss of one electron will make the by the names 2px, 2py, and 2pz, where the x, y, and
full outer shell of lithium with two electrons. z refer to the corresponding axes.

In the case of fluorine atoms, fluorine has seven 4.(c) The Pauli Exclusion Principle is the most
electrons in its outer shell; therefore if it gains one fundamental rule in organic chemistry. It was first
electron it will make fluorine with a full outer shell proposed by Wolfgang Pauli. According to Pauli,
of eight electrons. only two electrons can occupy any atomic orbital at
any given time, and to do so these two electrons
Lithium fluoride is formed by the transfer of one must have an opposite spins.
electron from lithium to fluorine. Lithium now bears
a positive charge due to the loss of electron 5.(a) The correct electronic configuration for
whereas fluorine bears the negative charge by Nitrogen (N) should be:
gaining the electron. The electrostatic attraction
between the oppositely charged atoms helps 1s 2px 2py
forming the bond. The type of bond where the bond 2s 2pz
forms due to the transfer of electron is defined as
an ionic bond. In organic chemistry, an orbital becomes occupied
only if the orbitals of lower energy are filled (e.g. 2s
2.(b) An NH 3 molecule is an example of a after 1s, 2p after 2s). Also, an orbital is not occupied
covalent bond since bond formation is possible due by a pair of electrons until other orbitals of equal
to the sharing of electrons by two atoms. energy are each occupied by one electron (e.g. 2px,
2py, 2pz). Nitrogen has seven electrons. On this
basis, a 1s orbital will be filled first with a pair of
electrons since this orbital has the lowest energy.
Another pair of electrons then occupies the 2s
In the above example, the outer shell of nitrogen orbital, which has the higher energy level compared
has three single electrons. By sharing one electron to the 1s but lower than the 2p. As previously

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