Download Unit 5 – Test Study Guide

Honors Chemistry
Study Guide – Unit 5: Periodic Trends
Test Date:
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Unit 5:
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Ions
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How is an ion different from an atom?
What is a cation? Anion?
How is a cation formed? How is an anion formed?
Are metals more likely to form cations or anions? What about nonmetals?
Know the number of valence electrons in main periodic families(1-8 valence e- possible)
Know the common charge that main group elements form (do not worry about the
transition metals) (ex: What ion would Na become? P? Al?, etc)
How do you name cations? How do you name anions?
Be able to determine the number of electrons in an ion vs. an atom of the same element
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Electron Configurations of Ions
o Be able to write electron configurations for ions such as Ca2+ of N3- etc…
o Remember that for transition metals, always remove the highest energy “s” electrons first,
and then remove the highest energy “d” electrons if you still need to remove more
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Development of the Periodic Table
o Dimitri Mendeleev – how did he organized the elements?
o Henry Moseley – how did he organize the elements?
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Effective Nuclear Charge
o Definition & trend across a period
o What does the effective nuclear charge depend upon?
 Hint: 2 factors that affect attraction between nucleus and electrons in an atom
o Zeff is responsible for all the trends as you move across a period (left to right)
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For example… the reason why atomic radius decreases across a period is because the
effective nuclear charge of the atom increases resulting in a greater attraction between
the nucleus & the electrons. This pulls the electrons in closer to the nucleus resulting in
a smaller atomic radius (This same logic can be manipulated for ALL of the periodic
trends)
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What is responsible for trends as you move down a column?
o Trends down a column are primarily based upon the fact that down a column Zeff does not
change much but a whole additional energy level (and many inner core electrons) has
been added to the atom resulting in greater electron shielding and electron repulsion
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For example: Ionization energy decreases down a column because with the addition of
another energy level and many more inner core electrons the atoms is much bigger.
This means the valence electrons are further away from the nucleus and they are less
attracted to the nucleus due to all the inner core electrons. This makes the removal of
an electron much easier resulting in a lower ionization energy as you move down a
column. (This same logic can be manipulated for ALL of the periodic trends)
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Atomic Radii
o Definition
o Trends (across a period & down a column)
o Ranking elements in order of increasing or decreasing atomic radii size
o Hint elements: Francium (largest) and Helium (smallest)
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Ionic Radii
o Definition
o Trends – if comparing all anions or all cations the trend follows that of atomic radius
o Comparing cations and anions to their neutral parent atoms
o Ranking elements in order of increasing or decreasing ionic radii size
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Ionization Energy
o Definition
o Trends(across a period & down a column)
o Hint Families – Noble Gases (highest) and Alkali Metals (lowest)
o Know about successive ionization energies (1st, 2nd, 3rd, 4th, etc.)
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Isoelectronic
o Know what this word means and be able to write and/or recognize isoelectronic series
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Electron Affinity and Electronegativity
o Definitions – know both terms and the difference between the two
o How does electron affinity relate to ionization energy?
o Trends (across a period & down a column)
o Why are negative energy values for electron affinity favorable and positive EA values are
unfavorable?
o What family has the lowest electron affinity? Why?
o Which family has the highest (most negative) electron affinity? Why?