Periodic Trends: Electronegativity, Metallic Character

Electronegativity An atom’s ability to pull electrons to itself in a

chemical bond

Cannot be directly measured

Trend: increases

decreases

How does this affect atoms?

Chemical bonding

Ionic BondsFormed between 2 atoms with a HUGE difference in

electronegativity---electron cloud is pulled closer to the more electronegative atom.

Covalent Bonds Atoms equally sharing electrons (nonpolar covalent)Atoms with a difference in electronegativity will exhibit

unequal sharing with the more electronegative atom pulling electrons toward it (polar covalent)

Example 1: Which of the following atoms is the most

electronegative?

A) S

B) As

C) P

D) Se

E) Cl

F) Br

Example 2: Which of these atoms are arranged based on

DECREASING electronegativity?

A) C > Si > P >As > Se

B) O > P > Al > Mg > K

C) Na > Li > B > N > F

D) K > Mg > Be > O > N

E) Li > Be > B > C > N

Metals, Nonmetals, Metalloids

How can you identify a metal?

What are its properties?

What about the less common nonmetals?

What are their properties?

And what the heck is a metalloid?

A Different Type of Grouping

Besides the 4 blocks of the table, there is another way of classifying element:

Metals

Nonmetals

Metalloids or Semi-metals.

The following slide shows where each group is found.

Metals

Metals are shiny, malleable, ductile, and are good conductors of heat and electricity.

They are mostly solids at room temp.

Want to LOSE valence electrons

Form positive ions

s block (not H and He), d/f blocks, some p block elements

Nonmetals

Nonmetals are the opposite.

No color, no shine

They are dull, brittle, nonconductors (insulators).

Gases at room temperature

Want to GAIN electrons

Form negative ions

p block elements, H and He

Transition MetalsMiddle of the periodic table

Forms positive ions, multiple types

Shine, malleable, ductile, good conductors

s/d orbitals—electrons lost from these subshells.

Metalloids/Semi-MetalsMetalloids, aka semi-metals are just

that.

They have characteristics of both metals and nonmetals.

They are shiny (like metals) but brittle.

And they are semiconductors.

“on the fence, middle of the road”

B, Si, As, Te, At, Ge, Sb, Po

Noble Gases Group 18 (He, Ne, Ar,

Kr, Xe, Rn)

Do NOT react with other elements

Atmospheric gases

Naturally in elemental form , single atoms

Not completely unreactive

Metallic CharacterThis is simply a relative measure of how easily

atoms lose or give up electrons.

Tendency to LOSE electrons

Related to atomic radius/ionization energy, how easy to remove electrons

Metallic Character

Decreases

Increases

Atoms with a tendency to GAIN electrons

Nonmetallic Character

Increases

Decreases

Homework

Beer’s Law Lab Report

Read over your lab procedure