Periodicity

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Periodicity

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Question 1

• Which element shows chemical behaviour similar to
  calcium?

strontium
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Wrong Answer!
Strontium and calcium both in group 2
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Question 2

• The following are three statements concerning the
  periodic table.
• The horizontal rows are periods and the vertical
  columns are called groups.
• Electronegativity decreases down any group and
  across a period from left to right.
• Reactivity increases down all groups.

I only
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Wrong Answer!
Electronegativity increases across a period from
left to right. Reactivity decreases down group 7.
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Question 3

• Which is the correct trend(left to right) across
  period 3 for the oxides?

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Wrong Answer!
Reactive metals form basic oxides reactive
non-metals form acidic oxides.
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Question 4

• What happens when chlorine water is added to an
  aqueous solution of potassium iodide?

Iodide ions are oxidized to iodine molecules.
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Wrong Answer!
Chlorine oxidizes the iodide ions Cl2(aq)
2I-(aq) ? 2Cl-(aq) I2(aq) Chlorine is a more
powerful oxidising agent than iodine.
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Question 5

• In general, atomic radii decrease

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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.
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Question 6

• In general, how do ionisation energies vary as
  the periodic table is crossed from left to right?

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Wrong Answer!
Shielding increases slightly cross the period but
this is more outweighed by the increase in
nuclear charge.
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Question 7

• Which one of the following series represents the
  correct size order for the various iodine species?

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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 electron-electron repulsion and
decreases the nuclear charge experienced by the
electrons.
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Question 8

• Which of the following has the lowest melting
  point?

Si
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Wrong Answer!
Alkali metals are soft metals with low melting
point.
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Question 9

• For which isoelectronic ions do ionic radii
  decrease with increasing nuclear charge?

Positive ions
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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.
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Question 10

• Which atom has the smallest atomic radius?

35Br
37Rb
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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.
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Question 11

• Which of the following properties of the halogens
  increase from F to I?
• Atomic radius
• Melting point
• Electronegativity

I and II only
I , II and III
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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.
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Question 12

• Which one of the following elements has the
  lowest first ionization energy?

B
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Wrong Answer!
Ionization energy decreases down a group and
increases across a period.
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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?

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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.
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Question 14

• On the periodic table, groups of elements show
  similarities in their chemical properties. This
  can be best explained by the

similarities in the electronic structures of the
atoms.
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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.
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Question 15

• Which properties are typical of of most
  non-metals in period 3 (Na to Ar)?
• They form ions by gaining one or more electrons.
• They are poor conductor of heat and electricity.
• They have high melting points.

I and II only
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Wrong Answer!
Most non-metals have low melting points because
they are simple molecular substances.
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Congratulations!