Unit 4 Chem

Define Metallic Bonding

• Electrons are delocalized / mobile (they are free to move throughout the solid)

• results from the electrostatic attraction between positive metal  ions and the surrounding mobile valence electrons.

Properties of Metallic Bonding

• Malleable - can be hammered into thin sheets

• Ductile - can be pulled into wires

• Solid (except for Hg - Mercury)

• Luster / Shiny (light reflects or bounces off the outer electrons)

• Good conductors of heat/electricity

  • electrons are able to slide into new positions without breaking the bonds
    

Define Electronegativity

How much an atom attracts shared electrons in a chemical bond

Define Alloy

• mixtures of 2 or more elements and at least one is a metal

Why would we use alloys like Brass, Pewter, Carbon Steel, or Bronze instead of pure metals?

Properties are often superior to those of their component elements.

Define Dipole

Occurs when there is a separation of electrical charge within a bond or a molecule—meaning one part is slightly positive and another part is slightly negative

A nonpolar covalent bond involves ______ of electrons.

equal sharing

A polar covalent bond involves ______ of electrons.

unequal sharing

An ionic bond involves ______ of electrons.

transfer

Define Percent Ionic Character

the degree to which a chemical bond between 2 atoms exhibits ionic character

What is the relationship between the percent ionic character of single bonds and the electronegativity difference?

As the electronegativity difference increases, the percent ionic character increases 

Define ionic bonding

In ionic bonding, electrons are transferred between a metal and nonmetal to achieve 8 valence electrons.

Properties of Ionic Compounds:

• Hard but brittle

• Good conductors when dissolved or molten  

• Soluble in water

• High melting/boiling points

• Crystalline solids (ions arrange in a repeating 3-D pattern)

When do Ions form?

Ions form when neutral atoms loses (+ charged Cation) or gains (- charged Anion) electrons

Dot Diagram for Lithium fluoride

Oppositely charged particles ____ one another; particles with the same charge ___ one another.

Oppositely charged particles attract one another; particles with the same charge repel one another.

What is an ionic compound?

neutral compound consisting of positive and negative ions. 

The electrostatic attraction that holds ions together in an ionic compound is

ionic bond

What can be used to illustrate electron transfer and the formation of ions?

Dot diagrams

What can be used to illustrate electron sharing?

Lewis Structures

Define Covalent Bonding

In covalent bonding, electrons are shared between nonmetal elements.  

When 2 electrons are shared, it is a ____covalent bond

When 4 electrons are shared, it is a ____ covalent bond

When 6electrons are shared, it is a ____ covalent bond  

When 2 electrons are shared, it is a single covalent bond

When 4 electrons are shared, it is a double covalent bond

When 6 electrons are shared, it is a triple covalent bond  

Covalent Bond properties

• Poor conductors of heat/electricity

• Lower melting and boiling points

• Most nonmetal elements are gases, some solids, and one is a liquid (Br)

Covalent Nomenclature

Only add prefix to first element if there is more than 1 atom and ALWAYS add prefix to second element

ex:
N₂O₅ = Dinitrogen pentoxide
NH₃ = Nitrogen trihydride (ammonia)

Complete Lewis Structure of:

Ch₄

Complete Lewis Structure of:

H_²0

Complete Lewis Structure of:

O_²

double bond

Complete Lewis Structure of and what kind of covalent bond it is:

N_²

triple bond

Complete Lewis Structure of and what kind of covalent bond it is:

CO_²

double bond

When metallic elements become ions they:

become positively charged and lose electrons (Cation)

What is the VSEPR theory used to predict?

Molecular Shape

According to VSEPR, molecules adjust their shapes to keep which of the following as far away as possible?

Pairs of valence electrons

VSEPR stands for ________ theory.

Valence Shell Electron Pair Repulsion

Name this molecular shape

Bent

Name this molecular shape

Tetrahedral

Name this molecular shape

Trigonal Planar

Name this molecular shape

Linear

Name this molecular shape

Trigonal Pyramidal

Name this molecular shape

Tetrahedral

Name this molecular shape

Linear

Name this molecular shape

Trigonal Pyramidal

Name this molecular shape

Trigonal Planar

Name this molecular shape

Linear

Define Bond polarity

- based on electronegativity difference
- distribution of charge within a bond  

Define Molecular polarity

- distribution of charge within a molecule
- based on bond polarities and shape

Molecular Polarity

Polar:
- Has lone pairs OR no lone pairs and asymmetrical

Nonpolar:

- No lone pairs and symmetrical

Determine Bond polarity and Molecular Polarity of:

Hydrogen Cyanide or HCN

Bond polarity

H = 2.1     C = 2.5      N = 3.0

  C—H bond  2.5 - 2.1 = 0.4

  C—N bond  3.0 - 2.5 = 0.5

Polar Bonds


Molecular Polarity

VSEPR shape = Linear
no lone pairs
asymmetrical

Polar Molecule

VSEPR