Chapter 6.3
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Transcript of Chapter 6.3
Chapter 6:The Periodic Table
Section 3:Periodic Trends
Describe trends among elements for shielding of nuclear charge;
Describe trends among elements for atomic size;
Explain how ions form; Define ionization energy; Describe trends among elements for ionization
energy and ionic radius; Define electronegativity; and Describe trends among elements for
electronegativity
Students will be able to…
Electrons (e-) are attracted to protons (p+) Trends relate to how those added protons
and electrons interact As you add 2nd p+ and e-, not much between
them Adding e- to 2nd energy level, have inner e-
shielding charge of added p+
As you move across the table, added e-
experience same level of shielding
The trend behind the trends...
Nuclear charge and shielding
Nuclear Charge
Shielding
Increases (adding protons)
Constant ( e- get same view of nucleus)
Incre
ase
s (ad
din
g p
roto
ns
Incre
ase
s (more
le
vels)
Atomic radius: half of distance between nuclei of two atoms of the same element when the atoms are joined
General trend: Increases down a group Decreases across a period
Trends in Atomic Size
Trends in Atomic Size
Atomic Radius From Shielding
Atomic Radius
Decreases (shielding constant, so p+suck in e-)
Incre
ase
s (levels w
in)
Ion: atom or group of atoms that has a charge
Cation: Ion with a positive charge
You’ll get a charge out of this...
Ion: atom or group of atoms that has a charge
Cation: Ion with a positive charge Anion: ion with a negative charge
You’ll get a charge out of this...
Cations always smaller than neutral atom◦ Lose one e-◦ More protons, suck in remaining
electrons Anions always bigger than
neutral atom◦ One extra e-
◦ Not as much positive charge to go around
How big is that ion?
Ionization energy: energy required to remove an electron from an atom in its gaseous state
Generally increases across periods ◦ Shielding constant ◦ Increased nuclear charge holds onto electrons ◦ As get closer to nonmetals, rather gain than lose
Generally decreases down groups ◦ Valence electrons further from nucleus ◦ Easier to pull off
Don’t even think about taking my e-
Don’t even think about taking my e-
Ionization Energy
Ionization Energy
Increases (shielding constant, p+hold onto e-)
Decre
ases (fu
rther
aw
ay, e
asie
r to
lose)
Electronegativity: ability of an atom to attract electrons when in a compound
Cs least electronegative element◦ Lowest ionization energy◦ Loses electrons easily, doesn’t attract them
•F most electronegative element
The flipside of ionization energy
Electronegativity
Electro-negativit
y
Increases (extra protons pull on electrons)
Decre
ases
(Sh
ield
ing
blo
cks
pu
ll)
Summary of trendsElectronegativity
Ionization Energy
Increases
Increases
Decrease
Increases
Constant
Decre
ases
Decre
ases
incre
ases
Incre
ases
Incre
ases
Atomic Radius
Nuclear Charge
Shielding
Describe trends among elements for shielding of nuclear charge?
Describe trends among elements for atomic size;
Explain how ions form? Define ionization energy? Describe trends among elements for ionization
energy and ionic radius? Define electronegativity? Describe trends among elements for
electronegativity?
Can you…?