Transcript Document 7188776

Periodicity
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Question 1
Which element shows chemical behaviour similar
to calcium?
sodium
boron
strontium
chlorine
Wrong Answer!
Strontium and calcium both in group 2
Question 2
The following are three statements concerning the periodic
table.
I. The horizontal rows are periods and the vertical
columns are called groups.
II. Electronegativity decreases down any group and
across a period from left to right.
III. Reactivity increases down all groups.
I only
II and III only
I and II only
I, II and III
Wrong Answer!
Electronegativity increases across a period from left to
right. Reactivity decreases down group 7.
Question 3
Which is the correct trend(left to right) across
period 3 for the oxides?
neutral to acidic
acidic to basic
increasingly basic
basic to acidic
Wrong Answer!
Reactive metals form basic oxides; reactive non-metals
form acidic oxides.
Question 4
What happens when chlorine water is added to an
aqueous solution of potassium iodide?
No reaction occurs
because chlorine is less
reactive than iodine.
Chlorine molecules are
oxidized to chloride ions.
Iodide ions are oxidized
to iodine molecules.
A purple precipitate of
iodine is formed.
Wrong Answer!
Chlorine oxidizes the iodide ions:
Cl2(aq) + 2I-(aq)  2Cl-(aq) + I2 aq)
Chlorine is a more powerful oxidising agent than iodine.
Question 5
In general, atomic radii decrease:
within a period from lower
to higher atomic number.
within a group from lower
to higher atomic number.
with an increase in the
number of isotopes of an
element.
with an increase in the
shielding of the nuclear
charge.
Wrong Answer!
Atomic radii decrease across a period due to the
increase in nuclear charge. Additional electrons enter the
same shell and only a small increase in shielding effect.
Question 6
In general, how do ionisation energies vary as the
periodic table is crossed from left to right?
They remain constant.
They decrease.
They increase to a
maximum and then
decrease.
They increase.
Wrong Answer!
Shielding increases slightly cross the period but this is
more outweighed by the increase in nuclear charge.
Question 7
Which one of the following series represents the
correct size order for the various iodine species?
I < I- < I+
I+ < I < I-
I < I+ < I-
I - < I < I+
Wrong Answer!
The removal of an electron from an iodine atom results in
an increase in the nuclear charge experienced by the
remaining electrons and hence the radius decreases.
The addition of an electron increases the electronelectron repulsion and decreases the nuclear charge
experienced by the electrons.
Question 8
Which of the following has the lowest melting
point?
Si
Al
Na
Mg
Wrong Answer!
Alkali metals are soft metals with low melting point.
Question 9
For which isoelectronic ions do ionic radii
decrease with increasing nuclear charge?
Both positive and
negative ions
Negative ions
Neither positive or
negative ions
Positive ions
Wrong Answer!
Removal of successive electrons increases the nuclear
charge experienced by the remaining electrons.
Additional of successive electrons increases the
electron-electron repulsion and decreases the nuclear
charge experienced by the electrons.
Question 10
Which atom has the smallest atomic radius?
37Rb
31Ga
35Br
20Ca
Wrong Answer!
Atomic radius decreases across the period. Each
subsequent electron enters the same shell, the same
increase in shielding effect is more than outweighed by
the increase in nuclear charge.
Question 11
Which of the following properties of the halogens
increase from F to I?
I. Atomic radius
II. Melting point
III. Electronegativity
I only
I and III only
I and II only
I , II and III
Wrong Answer!
Atomic radii increase down group 7 due to the presence
of additional electron shells, melting point increase down
the group due to an increase in va der Waals’ forces
caused by additional electrons.
Question 12
Which one of the following elements has the
lowest first ionization energy?
Mg
Na
B
Li
Wrong Answer!
Ionization energy decreases down a group and increases
across a period.
Question 13
0.01 mol samples of the following oxides were
added separately to 1 dm3 portions of water.
Which will produce the most acidic solution?
Al2O3(s)
Na2O(s)
SiO2(s)
SO3(g)
Wrong Answer!
Aluminium oxide, Al2O3 and silicon dioxide, SiO2 are
insoluble; sodium oxide, Na2O turns sodium hydroxide
solution (basic); sulfur trioxide, SO3 forms sulfruic acid,
H2SO4 solution.
Question 14
On the periodic table, groups of elements show
similarities in their chemical properties. This can
be best explained by the
differences in the
number of protons in the
nucleus of the atoms.
differences in the number
of neutrons in the
nucleus of the atoms.
similarities in the electronic
structures of the atoms.
similarities in the results of
emission spectrum analysis of
gaseous samples of a group.
Wrong Answer!
Each member has the same number of valence electrons
and hence form ions with the same charge or the same
number of covalent bonds.
Question 15
Which properties are typical of of most non-metals in period
3 (Na to Ar)?
I. They form ions by gaining one or more electrons.
II. They are poor conductor of heat and electricity.
III. They have high melting points.
I and II only
II and III only
I and III only
I, II and III
Wrong Answer!
Most non-metals have low melting points because they
are simple molecular substances.
Congratulations!