Transcript Chapter Two Atoms & The Periodic Table

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Main group elements (1,2,13-17)
Transition Metals (3-12)
Noble Gases (18)
Lanthanides and Actinides
Elements in same GROUP exhibit similar
chemical properties (due to their same
number of valence electrons)
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Nuclear Charge (Z) is # of protons in the
nucleus of an atom (atomic #)
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Effective Nuclear Charge (Zeff) is the actual
magnitude of positive charge “experienced”
by an electron
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A simultaneous phenomenon in which
electrons are attracted to the positive nucleus
while also repelled by other electrons
 Electrons “shield” other electrons from the
positive nucleus
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Increases steadily as you move across a
period
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Increases as you move down a group (but not
as significant as when you move across a
period)
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1)
2)
3)
For each pairing below, state which atom
would have the larger atomic radius
Na or K
F or O
Xe or Kr
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Minimum energy required to remove an
electron from an element in the gas phase
Creation of a cation (positive ion)
 First Ionization Energy (Easiest)
 Second Ionization Energy (Hardest)
 Etc
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Energy RELEASED when an atom in the gas
phase ACCEPTS an electron
Creation of an anion (negative ion)
Same general trend as ionization energy
 Increases across a period (due to higher Zeff)
 Decreases down a group (due to shielding)
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Increases from top to bottom and increases
from right to left
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Elements want to be just like Noble Gases
(very stable elements)
 Full outer shells (8 v.e. or 2. v.e. w/ Helium)
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They will lose or gain electrons to do this
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Let’s look at Na and Cl
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Write the electron configurations for the
following ions:
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Cr2+
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Ti3+
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Fe3+
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Write the electron configuration for the
following ion:
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Ag+
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S2-
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When atoms lose electrons (become cations),
radius decreases because of reduction in
electron repulsions (and shielding)
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When atoms gain electrons (become anions),
radius increases because of the increased
electron repulsion (spreads out)
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Elements that are in an isoelectronic series all
have the same electron configuration, but
NOT the same size
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Ex: Ca2+, K+, Ar, Cl-, S2-,P3-
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Name 2 elements you would expect to have
similar properties to Sr
Arrange Ca, Sr, and Ba in order of increasing
Ionization Energy
For each of the following pairs of elements,
indicate which will have the greater electron
affinity: Rb or Sr, C or N, O or F?
Identify the largest and smallest ion from the
following: Mg2+, N3-, O2-, Na+, C4-