Unit 4: The Periodic Tableand Periodic Trends

(Periodicity)

Chemistry

atomic number

Background on the Periodic Table

Dmitri Mendeleev: given creditfor Periodic Table (~1870)

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organized Table byincreasing atomic mass left spaces and predictedproperties of undiscoveredelements

• put elements inorder of increasing______________.

Mendeleev

Regions of the Tablemetals: left side of Table(1-3 valence e-); form cations

properties:

•lustrous(shiny)

•ductile(can pullinto wire)

•malleable(can hammerinto shape)

•good conductors(heat and electricity)•hard

nonmetals: right side of Table(5-7 valence e-; form anions by gaining electrons

properties: good insulators, poor conductorsgases or brittle solidsdull

Regions of the Table (cont.)

Br2I2S8Nebromineiodinesulfurneon

computer chips

metalloids (semimetals): “stair” between metalsand nonmetals

properties: (intermediate)in-between those of metalsand nonmetals; “semiconductors”

Regions of the Table (cont.)

(B, Si, Ge, As, Sb, Te, At)

Si and Ge

computer chips

metals

nonmetals

Periodicity

there are trends in properties of elements

-- left-right AND up-down trends

atomic radius: the size of a neutral atom

add a new energylevel each time

WHY?…increases as we go

…decreases as we go WHY?

Increase in nuclear charge

it has to do with…

Atomic Radii

Li

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

Be FONCB1.52 1.11

1.86 1.60

2.31 1.97

2.44 2.15

2.62 2.17

0.88 0.77 0.70 0.66 0.64

1.43 1.17 1.10 1.04 0.99

1.22 1.22 1.21 1.17 1.14

1.62 1.40 1.41 1.37 1.33

1.71 1.75 1.46

IA IIA IIIA IVA VA VIA VIIA

= 1 Angstrom

ionic radius:

cations anions

Ca atom Ca2+ ion Cl atom Cl1– ion

the size of an ion

20 p+ 20 e–

20 p+ 18 e–

17 p+ 17 e–

17 p+ 18 e–

Ca Ca2+ Cl Cl1–

cations lose electrons-smaller

Anions gain electronslarger

IA IIA IIIA IVA VA VIA VIIA

0.60 0.31

0.95 0.65

1.33 0.99

1.48 1.13

1.69 1.35

1.71 1.40 1.36

0.50 1.84 1.81

0.62 1.98 1.85

0.81 2.21 2.16

0.95

Li1+ Be2+

Na1+ Mg2+

Cl1-

N3- O2- F1-

S2-

Se2- Br1-

Te2- I1-

Al3+

Ga3+

In3+

Tl3+

Ca2+K1+

Sr2+Rb1+

Cs1+ Ba2+

Li

Na

K

Rb

Cs

ClSPSiAl

BrSeAsGeGa

ITeSbSnIn

Tl Pb Bi

Mg

Ca

Sr

Ba

1.52 1.11

1.86 1.60

2.31 1.97

2.44 2.15

2.62 2.17

0.88 0.77 0.70 0.66 0.64

1.43 1.17 1.10 1.04 0.99

1.22 1.22 1.21 1.17 1.14

1.62 1.40 1.41 1.37 1.33

1.71 1.75 1.46

Be B C N O F

= 1 Angstrom

AtomicRadii

IonicRadii

Cations: smaller than parent atoms

Anions: LARGERthan parent atoms

ionization energy: the energy required to remove an e– from an atom

As we go , 1st I.E….

As we go , 1st I.E….

•Nonmetals tend to gain therefore having a high first ionization energy.•Metals tend to lose-low first ionization energy

decreases.

increases.

(due to the shielding effect-increase in the number of energy levels)

Each successive ionization requiresmore energy than the previous one.

electronegativity: the tendency fora bonded atom toattract e– to itself

As we go , electronegativity…

As we go , electronegativity…

decreases.

increases.

electronegativity increases

•Nonmetals tend to gain therefore having a high electronegativity.•Metals tend to lose-low electronegativity

Reactivity of Metals

• Increases down a column – Reasons: Size (value of n), low ionization energy, and the shielding

effect• Decreases left to right across a period

– Reasons: Stronger nuclear charge and Increase in ionization energy

Reactivity of Nonmetals

• Increases left to right across a period– Why?

• Smaller in size• Stronger nuclear charge• Increased ionization energy

• Decreases down a column– Why?

• Decreased electronegativity• Larger in size

Reactivity Overview

• Fr-most reactive metal• F-most reactive nonmetal• Exception: Elements with half-

filled sublevels are more stable than those with empty orbitals