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Assignment 07
1- Arrange the following atoms in order of increasing atomic radius: N, K, As, Fr.
a) N < As < K < Fr
b) Fr < K < As < N
c) N < K < As < Fr
d) As < K < N < Fr
(The atomic radius increases toward the bottom left side of the periodic table.)
2- In which choice below are the elements ranked in order of increasing first-ionization energy?
a) Cl, S, Al, Ar, Si
b) Al, Si, S, Cl, Ar
c) Ar, Cl, S, Si, Al
d) Al, S, Si, Cl, Ar
(Ionization energy increases from left to right across a period.)
3- Which of these metals has the most negative electron affinity?
a) cadmium
b) cobalt
c) copper
d) calcium
e) chromium
(Adding one electron to this element completes its s subshell. This increases the stability of the
atom.)
4- Which of the following oxides is (are) ionic?
SO2, MgO, Li2O, N2O
a) SO2 and N2O
b) MgO and N2O
c) MgO and Li2O
d) MgO
e) N2O
(Ionic compounds usually form from the combination of a metal and a nonmetal.)
5- Which of the following is not true about oxygen?
a) Oxygen forms two unstable ions, peroxide and superoxide.
b) Dry air is about 80 percent oxygen.
c) The most stable allotrope is O2.
d) Ozone is toxic, whereas O2 is not.
(Air is about 20 percent oxygen and 80 percent nitrogen.)
6- Metallic character ________ from left to right across a period and ________ down a group of the
periodic table.
a) decreases, decreases
b) decreases, increases
c) increases, increases
d) increases, decreases
(Cesium, the most reactive metal (other than Francium which is not found in nature), is located at
the bottom left of the periodic table.)
7- Which of the following is the least reactive?
a) Ba
b) Sr
c) Ca
d) Mg
(Reactivity of alkaline earth metals increases down a group.)
8- What is the valence-shell electron configuration of the halogens?
a) ns2np6(n+1)s1
b) ns1
c) ns2np5
d) ns2np3
e) ns2
(The halogens have seven electrons in the valence shell.)
9- Which of the following pairs represents the correct order for the effective nuclear charge on the outermost
valence electrons?
a) O > F
b) Fe > Ti
c) Si >Cl
d) K > Mg
(Fe has more protons in the nucleus and there are no more electrons in the core of iron when
compared to titanium.)
10- Which of the following is correctly arranged with respect to the size of the atom/ion?
(i) S < S1− < S2−
(ii) Mg2+ < Na+ < Ne
(iii) Ni < Cu+ < Zn2+
a) i and iii only
b) ii and iii only
c) iii only
d) ii only
e) i and ii only
f) i only
(The more negative the charge on the atom, the larger it is. The radii of isoelectronic species
decrease with atomic number. The more positive charge on the ion/atom for an isoelectronic series,
the smaller is the radius of the ion/atom.)
11- Arrange the following atoms in order of increasing distance of the n = 4 electron shell from the nucleus: Rb,
Ca, As, Ir, and Zr.
a) Ir < Rb < Zr < Ca < As
b) Ca < As < Rb < Zr < Ir
c) Ir < Zr < Rb < Ca < As
d) Ir < Zr < Rb < As < Ca
e) Ir < Rb < Zr < As < Ca
(The distance of the n=4 shell from the nucleus increases as the nuclear charge of the elements
decreases in this series of elements.)
12- Which of the following sets of elements is in the incorrect order of increasing atomic radius (smallest one
first, etc.)?
a) Cl, S, O
b) S, As, Sn
c) Cl, Br, I
d) Se, As, Sb
e) P, Si, Al
(Atomic radius decreases across a period, but increases down a group. Sulfur has a larger radius
than oxygen, making this ordering of atomic radii incorrect.)
13- If successive ionization energies are numbered 1, 2, 3, etc., arrange the following in increasing order (lowest
one first, etc.).
A: I1 for Li
B: I1 for Na
C: I2 for Li
D: I2 for Be
a) B < C < A < D
b) A < B < C < D
c) B < A < C < D
d) A < B < D < C
e) B < A < D < C
(First-ionization energies decrease down a group. The second ionization energy for Li would
involve removing an electron from a stable inert gas-like electron configuration. This would be
much larger than the second ionization energy for Be, where the second-ionization step results in
the formation of an inert gas like electron configuration.)
14- For each of the following pairs, which element will have the greater metallic character: Li, Be and Li, Na?
a) Li, Li
b) Be, Na
c) Be, Li
d) Li, Na
(Metallic character increases toward the bottom left side of the periodic table.)
15- Which of the following is not a property of an alkali metal?
a) Alkali metals are highly reactive towards oxygen and water.
b) Alkali metals can be cut with a dull knife.
c) Alkali metals have relatively low melting points.
d) Alkali metals are good conductors of electricity.
e) Alkali metals are harder than alkaline earth elements.
(Alkali metals are actually softer than alkaline earth elements. Magnesium is sufficiently hard that
some engine parts are made of alloys containing magnesium.)
16- Which two noble gases can form stable compounds with fluorine?
a) Ar, Xe
b) Ne, Ar
c) Ne, He
d) Ar, Kr
e) Kr, Xe
(Both of these can engage in the formation of chemical compounds, typically by reacting with
fluorine or chlorine.)
17- Which of the following is balanced correctly?
a) 2Ca(s) + 2 H2O(l)  2Ca(OH)2(aq)
b) 2Ca(s) + Cl2(g)  2 CaCl(s)
c) Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g)
d) Ca(s) + Cl2(g)  CaCl2(s)
e) 2 Ca(s) + Cl2(g)  2CaCl2(s)
(The charge on calcium is 2+, while the charge on chlorine is 1−.)
18- Which of the following oxides is most acidic?
a) CaO
b) Li2O
c) Al2O3
d) CO2
(Most nonmetal oxides are acidic.)
19- Which of the following has the largest first-ionization energy?
K, Ca, Fe, Cu, Ge, S
a) S
b) Ge
c) Cu
d) Fe
e) K
f) Ca
(The ionization energy increases across a period and up a group. Sulfur is a nonmetal. Nonmetals
tend to gain electrons rather than lose electrons in chemical reactions.)
20- Which of the following has the highest ionization energy? Na, Na+, K+, Mg2+?
a) Na+
b) Mg2+
c) K+
d) Na
(This magnesium ion has the largest positive charge of the list of atoms and ions, and has an inertgas-like electron configuration.)
21- Which of the following are metalloids?
a) O, S, Se
b) As, N, P
c) As, Si, Ge
d) F, Cl, Br
e) Si, C, Ga
(The metalloids are the elements between the metals and the nonmetals on the periodic table.)
22- Write a balanced chemical equation for the reaction that occurs when sulfur reacts with potassium. Sulfur is
found in elemental form as S8.
a) 16K(s) + S8 (s)  8K2S(s)
b) K(s) + S8(s)  no reaction
c) K(s) + S8 (s)  KS(s)
d) K(s) + S2(s)  KS2(s)
(Potassium forms a 1+ cation, while sulfur forms a 2- cation.)
23- Selecting from the choices offered, what is the most likely identity of "X2" in the reaction
4Ga + 3X2  2Ga2X3?
a) F2
b) Cl2
c) O2
d) Br2
e) N2
(Ga forms a 3+ cation; oxygen forms a 2− anion, which balances the charge in the formula.)
24- Compare the elements rubidium and strontium with respect to the following properties: most common ionic
charge and first-ionization energy (I1 ). Which of the following choices is correct?
a) Rb+, Sr2+, I (Sr) < I (Rb)
b) Rb+, Sr2+, I (Rb) < I (Sr)
c) Rb+, Sr+, I (Rb) < I (Sr)
d) Rb2+, Sr2+, I (Rb) < I (Sr)
e) Rb+, Sr+, I (Sr) < I (Rb)
(The charge on each metal is equal to their group number. Ionization energy increases across a
period of the periodic table from left to right.)