nuclear charge increases electron shielding increases electron shielding remains constant

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PERIODIC TRENDS Coulomb’s Law Nuclear Charge • Electron Shielding Atomic Size 1st Ionization Energy • Electronegativit y • Reactivity

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PERIODIC TRENDS

• Coulomb’s Law• Nuclear Charge• Electron Shielding• Atomic Size• 1st Ionization Energy• Electronegativity• Reactivity

TRENDS

Nuclear Charge Increases

Nuc

lear

Cha

rge

Incr

ease

sEl

ectr

on S

hiel

ding

Incr

ease

s

Electron Shielding Remains Constant

1

HHydrogen

1

3

LiLithium

7

11

NaSodium

23

1s22s22p63s1

1s22s1

1s1

ATOMIC SIZE?

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

Atomic Size

Atomic Size

TRENDS

Nuclear Charge Increases

Nuc

lear

Cha

rge

Incr

ease

s

Atom

ic S

ize

Incr

ease

Elec

tron

Shi

eldi

ng In

crea

ses

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.

TRENDS

Nuclear Charge Increases

Nuc

lear

Cha

rge

Incr

ease

s

Atom

ic S

ize

Incr

ease

Elec

tron

Shi

eldi

ng In

crea

ses

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

Incr

ease

Elec

tron

Shi

eldi

ng In

crea

ses

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

Incr

ease

Elec

tron

Shi

eldi

ng In

crea

ses

Electron 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

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.

ESSAY QUIZ GRADE: Explain periodic trends in first ionization energy, electronegativity, atomic size and reactivity in terms of Coulomb's

law, nuclear charge and electron shielding. BE THOROUGH!