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Chemistry 0871 / Chemistry 0983
Learning Centre
Atomic Theory & Structure
EXERCISES
A. True or false:
1) An atomic orbital is a region in which we may expect to find an electron.
2) The maximum number of p electrons in the first orbital shell is six.
3) In the ground state, electrons tend to occupy orbitals of the lowest possible
energies.
4) The angular quantum number, ℓ, specifies the shape of the electron cloud around
the nucleus.
5) Dalton’s Atomic Theory states that all atoms are composed of protons, neutrons
and electrons.
6) The electron was discovered by J.J. Thomson.
7) The Pauli Exclusion Principle states that atoms of two different elements can
have no two quantum numbers alike.
8) The third orbital shell can contain a maximum of eight electrons.
9) The principal quantum number, n, indicates the energy levels of the electrons
relative to their distance to the nucleus.
10) In a given atom, electrons in the 3s and 3p orbitals will have the same n and ℓ
quantum numbers.
11) The fourth orbital shell can contain a total of 32 electrons.
12) The energy level of a 3d electron is higher than that of a 4s electron.
13) The larger the value of n, the greater the average distance of the electron from
the nucleus.
14) All the elements in a group possess essentially the same outer-shell electron
structure.
15) The Hund Principle states that electrons occupy the lowest-energy orbitals
available before entering the higher-energy orbitals.
16) The electron structure for a carbon atom is 1s²2s²2px².
17) The third orbital shell can contain nine electron orbitals.
18) The proton was discovered by James Chadwick in 1932.
19) A p orbital is spherically symmetrical around the nucleus.
20) The symbols for the four quantum numbers are n, ℓ, m, and s.
© 2013 Vancouver Community College Learning Centre.
Student review only. May not be reproduced for classes.
Authoredby
byEmily
Gordon
Wong
Simpson
21) An atom of nitrogen has 2 electrons in a 1s orbital, 2 electrons in a 2s orbital, and
1 electron in each of three different 2p orbitals.
22) Dalton’s Atomic Theory states that electrons exist in orbits which have specific
energy and shape.
23) An s orbital is spherically symmetrical about the nucleus.
24) The 2px, 2py and 2pz electron orbitals are in the same energy state.
25) In the ground state, all electrons are in the highest available energy level.
26) All the elements in a group have the same value of n.
27) A half-filled subshell is very unstable.
28) A 2s electron is in a lower energy state than a 2p electron.
29) The kernel is what is left after Roland Moutal had corn on the cob for lunch.
30) The number of orbitals in a d subshell is five.
B. What is the maximum number of electrons that can be in each of the following
orbitals?
1) 2p
3) 6p
5) 4d
7) 3f
2) 4p
4) 3s
6) 4f
C. Write the electron configuration for the Group 13 (or Group IIIA) elements. How are
they similar?
D. Write the (unabbreviated) electron configurations of the following. Identify the
species which are isoelectronic (have the same number of electrons):
1) Ne
4) C
2) K+
5) Cℓ−
3) O2−
6) F−
E. Identify the elements with the following electron configurations:
4) [Ar]4s23d104p3
1) [Ne]3s23p5
2) [Ar]4s23d104p6
5) [Kr]5s24d105p4
3) [Ar]4s23d1
6) [Xe]6s1
F. Derive the electron configurations of the following:
3) 15P
1) 14Si
2)
19K
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Student review only. May not be reproduced for classes.
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G. Derive the electron configurations of the following species:
1) Co
3) Aℓ
2) Co3+
4) Aℓ3+
5) As
6) As3−
H. Derive the electron configurations for the following species, which are classified as
exceptions, since they do not follow the normal filling order, but instead follow the rule
that a half-filled or completely filled orbital is more stable:
1) Cu
3) Ag
2) Cr
4) Au
I. Determine the number of unpaired electrons in the following:
1) C
3) Mg
5) Na
7) Fe2+
2) Be
4) Si
6) F−
8) Mn2+
SOLUTIONS
A. (1) true (2) false [0] (3) true (4) true (5) false (6) true (7) false
(8) false [16 electrons] (9) true (10) false [same value of n, but not ℓ.] (11) true
(12) true (13) true (14) true (15) false [The Hund Principle has to do with halffilled orbitals.] (16) false [1s²2s²2p²] (17) true (18) false [neutron] (19) false [It is
propeller-shaped.] (20) true (21) true (22) false [Dalton’s theory was from before
the discovery of the electron.] (23) true (24) true (25) false [They have the lowest
energy state.] (26) false [Electrons and orbitals have values for n; elements don’t.]
(27) false [Hund’s Principle says that they are more stable than a partially filled one.]
(28) true (29) false [The kernel is the “core” of an atom: the nucleus and the nonvalence electrons.] (30) true
B. (1) 6 (2) 6 (3) 6 (4) 2 (5) 10 (6) 14 (7) There’s no such thing as a 3f orbital.
C. Boron: 1s22s22p1; aluminum: [Ne]3s23p1; gallium: [Ar]4s23d104p1;
indium: [Kr]5s24d105p1; thallium: [Xe]6s25d104f146p1. The highest-energy orbital
occupied has a full s orbital and one electron in the p orbital.
D. (1) 1s22s22p6 (2) 1s22s22p63s23p6 (3) 1s22s22p6 (4) 1s22s22p2
(5) 1s22s22p63s23p6 (6) 1s22s22p6 The neon, oxide and fluoride are isoelectronic;
so are the potassium and chloride.
E. (1) chlorine (2) krypton (3) scandium (4) arsenic (5) tellurium (6) cesium
F. (1) [Ne]3s23p2 (2) [Ar]4s1 (3) [Ne]3s23p3
G. (1) [Ar]4s23d7 (2) [Ar]3d6 (3) [Ne]3s23p1 (4) [Ne] (5) [Ar]4s23d104p3
(6) [Ar]4s23d104p6
H. (1) [Ar]4s13d10 (2) [Ar]4s13d5 (3) [Kr]5s14d10 (4) [Xe]6s14f145d10
I. (1) 2 (2) 0 (3) 0 (4) 2 (5) 1 (6) 0 (7) 4 [Not 6. The configuration is [Ar]3d6.
Electrons in transition metals are taken from the orbitals with the highest value for
n first. Iron does not behave like an exception as in part H.] (8) 5 [Not 3.]
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Student review only. May not be reproduced for classes.
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