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…?