GENERAL CHEMISTRY
YUFIDANI
L2C009018
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1. The radii of the sodium and potassium ions are 102 pm and 138 pm, respectively.
Which compound has stronger ionic attractions, sodium chloride or potassium
chloride?
Answer : The energy of attraction (or repulsion) between two particles is directly
to the product of the charge and inversely proportional to the distance
between them.
ch arg e1 ch arg e2
We have equation Energy
dis tan ce
Smaller ion attracts each other ion more strongly than larger ions,
because their charges are closer together.
Sodium is smaller than potassium, so sodium chloride(NaCl) has
stronger ionic attraction than potassium chloride(KCl).
2. Does potassium nitrate (KNO3) incorporate ionic bonding, covalent bonding, or
both? Explain
Answer : KNO 3
K + NO 3
The anion NO 3 (nitrate) is polyatomic ion, which consist of four
covalently bonded atoms. NO 3 incorporate covalent bonding because
the elements of nitrate share electrons.
And then ionic bonding occurred between K (as cation) and NO 3 (as
anion). Potassium atom losses 1 electron and forms a potassium cation
(K ), and nitrate gains an electron and becomes a nitrate anion (NO 3 ).
So KNO 3 incorporate both ( ionic bonding and covalent bonding).
3. An X-ray has a wavelength of 1,3
of this radiation?
Answer : E = nhv
, calculate the energy (in joule) of one photon
= nh c
(3 108 m )
s
= (1) ( 6,626 x 10 J.s)
10
(1,3 10 m)
-15
= 1,529 x 10 joule
-34
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4. The following quantum number combinations are not allowed, assuming the n and
ml values are correct. Chance the l value to create an allowable combination
a. n = 3 l = 0 ml = -1
b. n = 3 l = 3 ml = +1
c. n = 7 l = 2 ml = +3
d. n = 4 l = 1 ml = -2
Answer : The orbital filling order
1s
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
7s
7p
a. n = 3
l=0
ml = -1
-1 0 +1
If the l value is 0, it’s false, because l=0 has configuration 3s, as we
know that s just has one orbital, in fact ml=-1 minimal has three
orbitals(3p), so we can create l value is 1 (l = 1).
b. n = 3
l=3
ml = +2
-2 -1 0 +1+2
If the l value is 3, it’s mean that the electron 3f, and it’s false, because
in electron filling order 3f is nothing. If ml = +2, the electron must be
3p. So we can create l value is 2 (l = 2).
c. n = 7
2
l=2
ml = +3
-3 -2 -1 0 +1 +2 +3
If the l value is 2, it’s mean that the electron 7d, and it’s false, because
nothing 7d. And the biggest possibility is 7p, but the ml value also
must be changed becomes ml = +1. So we can create l value is 1 (l =
1).
d. n = 4
l=1
ml= -2
-2 -1 0 +1 +2
If the l value is 1, it’s false, because l=1 has configuration 4p, as we
know that p has three orbitals, in fact ml=-2 has five orbitals, so we
can create l value is 2 (l = 2)
5. Write a full set of quantum number for the following:
a. outermost electron in an Rb atom
b. the electron gained when an S- ion becomes an S2- ion
c. the electron lost when an Ag atom iones
d. the electron gained when an F- ion forms from an F atom
_
Answer : a.
37
e = 37
Rb
[Kr] 5s 1
n=5
b.
2
16 S
l=0
m=0
s=+
1
2
s=-
1
2
s=-
1
2
_
e = 18
[Ne] 3s 2 3p 6
n=3
l=1
m=1
_
c. Ag
Ag + e
_
47 Ag
e = 46
[Kr] 5s 2 4d 8
n=4
l=2
m=0
3
_
d. F + e
F
_
9
e = 10
F
1s 2 2s 2 2p 6
n=2
l=1
m=1
s=-
1
2
6. Palladium (Pd, Z=46) is diamagnetic. Draw partial orbital diagram to show which
of the following electron configurations is consistent with this fact:
a. [Kr] 5s2 4d8
b. [Kr] 4d10
c. [Kr] 5s1 4d9
Answer : a. [Kr] 5s2 4d8
5s
4d
b. [Kr] 4d10
5s
4d
c. [Kr] 5s1 4d9
5s
4d
Palladium is diamagnetic. Diamagnetic is a species with all electrons
paired. So the electron configuration that consistent with this fact is
[Kr] 4d10.
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7. Both nitrogen and bismuth are members of group 5A. Which is more metallic?
Explain your answer in term of atomic properties
Answer :
INCREASES
METALLIC BEHAVIOR
N
Bi
Metallic behavior decreases left to right and increases top to bottom in
the periodic table. Metals tend to lose electrons during chemical
reactions because they have low ionizations energies.
As we move across a period, it becomes more difficult to lose an
electron because of ionization energies (IE) increases and easier to
gain electron (electron affinities/EA becomes more negative).
So, it’s means that Bismuth more metallic than Nitrogen.
8. When liquid benzene (C6H6) boils, does the gas consist of molecules, ions, or
separates atoms? Explain scientifically
Answer : Benzene consist of six atoms of carbon and six atoms of hydrogen that
bonded circle pattern (sickles). Benzene including aromatic compounds.
Benzene has molecule structure like this
Symmetries structure shows six atoms of carbon on benzene, and circle in
the center shows crowd of aromatic on benzene molecule.
Crowd of aromatic is contained by six electrons from p orbital. This
process is electron delocalization.
Crowd of electron is the main character of aromatic compound and makes
benzene molecule more stabile.
So, when liquid benzene boils, the gas consists of molecules.
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