Transcript THE Periodic Chart

The Period chart and Its Patterns
may seem like a
mystery…
CASE OF THE PERIODIC TRENDS!
You find a small scroll of paper…
Using your
keen intellect,
what do you
observe?
pm= picometer 10-12: it’s a trillionth of a meter!
2) What do you notice about elements in
the same group?
Why?
3 levels
Na
4 Levels
K
3) As you move down a group, the number
of energy levels increase = larger radii
4) What is the trend
within a period?
This time, they both
have 3 Energy levels
5) As you move across a
period, the elements
have more protons. More
protons mean a greater
nuclear pull and pull the
electrons closer to the
nucleus = smaller atoms!!
P
Cl
• On the back of the note….
• There’s a small picture!
It appears to be the sizes of ions Within a period?
Within a group? What do you notice?
What do you notice?
Mg
Al
+3
Al
P
Why?
Mg+2
Ca
Ca+2
Why?
Predict
the size
of the
Cl-1 ion!
P-3
Why?
Cl
?
-1
Cl
Dear gang..hopes this helps!
1) More energy levels means wider/bigger
atoms/ions!
2)Within a period, the more protons, the
greater the pull from the nucleus = smaller
atoms!
3) If an ion loses electrons, it will become
Covertly,
smaller
Mr. S.
4) If an ion gains electrons, it will become
larger.
SAMPLE PROBLEM
Atomic Radii
Ranking Elements by Atomic
Size from largest to smallest
(a) Ca, Mg, Sr
(c) C-2, C+2, C
1 2 3 (b) K, Ga, Ca
1 2 3
1 2 3
SOLUTION:
(a) Sr > Ca > Mg
These elements are in Group 2A(2).
(b) K > Ca > Ga
These elements are in Period 4.
(c) C-2 > C > C+2
The carbon ion gaining electrons is
the largest, the normal atom, and
then the ion losing electrons.
Hey gang, You need to know these words to proceed
any further! I’ve used disappearing ink… -Mr. S.
• 1st ionization Energy- how much
energy is needed to remove the first
valence electron.
• Electronegativity- how strongly an
atom pulls another atom’s valence
e- to itself to form bonds.
Consider any electron in the second energy level…
electron
nucleus
1st
2nd
3rd
4th
Shielding
Recap:
Electron in 2nd
energy level
1st energy
level (shielding
nucleus)
Nucleus (with
+ protons)
The electrons create a “shield” that limits the outer electrons from
the positive nuclear pull.
Note that the 1st energy level is between these electrons and the nucleus
By definition, the
first ionization
energy of an
element is the
energy needed to
remove the
outermost, or
highest energy,
(valence) electron
from an atom.
9) What happens to
st
1
Ionization Energy in a group?
10) The more energy levels, the
more shielded the electrons are
and it require less energy to
F
remove an electron.
1681.0
Cl
1251.1
Br
1139.9
11) What is the trend in I.E. as you move across a period?
12) Why? More
protons =
stronger nuclear
pull! The greater
the pull from the
nucleus, the
more energy is
required to
remove the
electron.
O
8
1313.9
F
9
1681.0
10
Ne
2080.6
SAMPLE PROBLEM
Ionization
Energy
(a) Sb, Te, Sn
1 2 3
Ranking Elements by their
Ionization Energies, highest to
lowest:
(b) S, O, Te
1 2 3
SOLUTION:
(a) Te > Sb > Sn
Period 5 elements - IE increases
across a period.
(b) O > S > Te
These elements are in group 15
and energy decreases as you move
down a group.
Electronegativity is the ability
of an atom to attract electrons
to form a chemical bond.
Electronegativity
14) What happens to Electronegativity in a group?
15) More energy levels shield the electrons and
the attractive forces get smaller.
Electronegativity
16) What happens to E.neg across a period?
17) More protons = a greater nuclear pull
which pulls the electrons with a greater force!
Summary
Moving Top to Bottom
• Atomic Radius Increases
• Ionization Energy Decreases
• Electronegativity Decreases
• The effects can be explained by
additional energy levels, and the
shielding of the nucleus reducing the
attractive forces from the nucleus.
Summary of Periodic Trends
Moving Left to Right
•
•
•
•
Atomic Radius Decreases
Ionization Energy Increases
Electronegativity Increases
The effects can all be explained
by increasing protons and nuclear
pull from the nucleus and pulling
the electrons closer.
Excellent Job Gang!!!
THE END
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