Electrostatic Force Opposites Attract Like Charges Repel.
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PERIODIC TRENDS
• Nuclear Charge• Electron Shielding• Atomic Size• 1st Ionization Energy• Electronegativity• Reactivity
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F = Kq1q2r2
Coulomb’s Law
Coulomb’s Law
• Coulomb's inverse-square law, is a law of physics describing the electrostatic interaction between electrically charged particles.
Electrostatic ForceOpposites AttractLike Charges Repel
Inverse Square Law
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F = Kq1q2r2
Q1 Q2Q1 Q2
More Force Less Force
Q = Charge r = distance K = constant
The greater the charge the greater the force.The closer the charged particles are, the
stronger the electrostatic force.
Inverse Square Law
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F = Kq1q2r2
e-1 p+1r=1
e-1 p+1r=2
e-1 p+1r=3
Inverse Square Law
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F = Kq1q2r2
e-1 p+1r=1
e-1 p+1r=2
e-1 p+1r=3
If you double the charge you double the force. If you triple the charge you triple the force.
If you double the distance you reduce the force by 4 times as much. If you triple the distance you reduce the force by 9x as much.
Inverse Square Law
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F = Kq1q2r2 Electrostatic Force
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F = Gm1m2
r2 Gravitational Force
Magnetic Force
Sound Intensity Light Intensity
Field Strength
Inverse Square Law
Assignment
1. Opposite Charges ________________. Like charges ________________. If charge increases then force ____________. If distance increases then force _________.
2. Explain the inverse square law and its importance.
3. If the value of the charge on an object quadruples, what happens to the value of the electrostatic force?
4. If two charges separated by 1 nanometer are moved twice as far apart, what happens to the value of the electrostatic force between them?
5. If the distance between two charges is cut in half, what happens to the value of the force?
6. If you double both the total charge of an object and the distance between those two objects, what happens to the value of the electrostatic force?
7. Considering the actual charge of a proton is 1.602176565(35)×10−19 C and an electron is -1.602176565(35)×10−19 C what would be the electrostatic force between them at a distance of 1 nanometer (1.0 × 10-9 meters). Assume K = ke = 8.9875517873681764×109 N·m2/C2.
Nuclear Charge
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Total electric charge in a nucleus. It is equal to the number of protons.
The Nucleus is what attracts electrons.
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s1
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s22s1
1s1
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s22s22p63s1
1s22s1
1s1
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s22s22p63s1
1s22s1
1s1
As you go down a group or column in the periodic table the number of energy levels increases.
Pattern?
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s22s22p63s1
1s22s1
1s1
As you go down a group or column in the periodic table the number of energy levels increases.
SPDF Blocks
1
HHydrogen
1
3
LiLithium
7
11
NaSodium
23
1s22s22p63s1
1s22s1
1s1
ATOMIC SIZE?
TRENDS
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
se
Atomic Size
5
BBoron
1
3
LiLithium
7
4
BeBeryllium
23
5
BBoron
1
3
LiLithium
7
4
BeBeryllium
23
5
BBoron
1
3
LiLithium
7
4
BeBeryllium
23
5
BBoron
1
3
LiLithium
7
4
BeBeryllium
23
5
BBoron
11
3
LiLithium
7
4
BeBeryllium
9
As you go across a period the number of energy levels remains constant.
Pattern?
Electron Shielding
--
-- -
-
-
-
-
- -+11Electrons in an atom can shield each other from the pull of the nucleus.
As you go across a period electron
shielding is constant.
As you go down a group electron
shielding increases.
TRENDS
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
seEl
ectr
on S
hiel
ding
Incr
ease
s
Electron Shielding Remains ConstantAtomic Size does what????
5
BBoron
11
3
LiLithium
7
4
BeBeryllium
9
As you go across a period atomic size decreases because the pull of the nucleus (nuclear charge) increases but electron shielding remains constant. The nucleus is able to pull the electrons closer (Coulomb’s law).
Atomic Size
TRENDS
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
seEl
ectr
on S
hiel
ding
Incr
ease
s
Electron Shielding Remains ConstantAtomic Size Decreases
1st Ionization Energy
--
-- -
-
-
-
-
- -+11The energy required to remove the outermost electron from an atom.
As you go across a period 1st ionization
energy increases.
As you go down a group 1st ionization energy decreases.
Additional Electron shielding and increased distance from the nucleus makes removing the outermost electron much easier.
Increasing nuclear charge without any additional shielding makes removing the outermost electron more difficult.
Why does the high 1st ionization energy of the Noble gasses indicate?
TRENDS
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
seEl
ectr
on S
hiel
ding
Incr
ease
s
Electron Shielding Remains ConstantAtomic Size Decreases1st Ionization Energy Increases
1st Io
niza
tion
Ener
gy D
ecre
ases
Electronegativity
--
-- -
-
-
-
-
- -+11A measure of an atom or group of atom’s tendency to attract electrons
As you go across a period Electronegativity increases.
As you go down a group Electronegativity
decreases.
Additional Electron shielding and increased distance from the nucleus makes adding a new electron more difficult
Increasing nuclear charge (pull) without any additional shielding makes makes adding an electron easier.
Fluorine is the most electronegative element.
What about the Noble gasses?
TRENDS
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
seEl
ectr
on S
hiel
ding
Incr
ease
s
Electron Shielding Remains ConstantAtomic Size Decreases1st Ionization Energy Increases
1st Io
niza
tion
Ener
gy D
ecre
ases
Electronegativity Increases
Elec
tron
egati
vity
dec
reas
e
Reactivity
For now we can think of an atom’s
tendency to lose or gain electrons as its
reactivity.
So atoms that lose electrons very easily or
have a strong affinity for electrons are considered
the most reactive.
Nuclear Charge Increases
Nuc
lear
Cha
rge
Incr
ease
s
Atom
ic S
ize In
crea
seEl
ectr
on S
hiel
ding
Incr
ease
sElectron Shielding Remains ConstantAtomic Size Decreases1st Ionization Energy Increases
1st Io
niza
tion
Ener
gy D
ecre
ases
Electronegativity IncreasesEl
ectr
oneg
ativi
ty d
ecre
ases
Metals: Reactivity decreasesM
etal
s: R
eacti
vity
Incr
ease
Non
met
als:
Rea
ctivi
ty d
ecre
ases
Nonmetals: Reactivity Increases
€
F = Kq1q2r2
Assignment
---
- --
-
-
-
- -+11
1st Ionization energy is the amount of energy needed to remove the outermost electron in an atom.
2nd Ionization Energy level is the energy required to remove the next electron.
QUESTION: Will sodium have a higher or lower 2nd Ionization energy compared to its first Ionization energy? Explain this in terms of the inverse square law, Coulomb’s law and electron shielding.
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