6.1 Review

436 kJ of energy must be supplied to break the bonds in _____

1 mol of H2 molecules

In order for a substance to be able to conduct a current or heat, the substance needs two things:

1. Movable particles 2. Charged particles

When two bonded hydrogen atoms are at their lowest potential energy, what is their distance

75 pm

Why can metals conduct electricity?

Because they have valence electrons that move freely around in their molecular orbitals

How can we estimate the attraction each atom will have and predict the type of bond?

By using electro negativity values

Difference in Electronegativity values will ______.

Determine Bond Type

Explain the role and location of electrons in a covalent bond?

Electrons are lost gained or shared in a covalent bond. These electrons are located on each atom in this bond called a molecular orbital.

When an ionic bond forms, what happens to the electrons?

Electrons are lost or gained in an ionic bond

Non-Polar Covalent

Equal Sharing

How will electrons be shared in a covalent bond

Equally or unequal

Example of δ+ and δ-

Hδ+Fδ-

Physical properties for covalent compounds

Melting Point= Low to high Solubility in Water= variable Conductivity as a Solid= does not Hardness=Medium Brittleness=Brittle

Physical Properties for metallic

Melting Point= Low to high Solubility in Water=Insoluble Conductivity as a Solid=does well Hardness=soft-hard Brittleness=nonbrittle

Physical properties for Ionic compounds

Melting Point=High Solubility in Water=Soluble Conductivity as a Solid=Does Not Hardness=Hard Brittleness=Brittle

Key

Nature prefers to be at its lowest energy possible

•Distinguish between nonpolar and polar covalent bonds based on electronegativity differences.

Non-Polar--> covalent bond in which the bonding electrons are equally attracted to both bonded atoms. Polar---> a covalent bond in which a shared pair of electrons is held more closely by one of the atoms.

Compare the physical properties of substances that have different bond types, and relate bond types to electronegativity differences.

Non-Polar--> even electron distribution- even electron clouds Polar--> uneven electron distribution- uneven electron clouds Ionic--> electron clouds are separated - uneven clouds far apart

Predicting Bond Character

Nonpolar covalent--> even electron distribution Polar covalent--> uneven electron distribution Ionic--> separate electron clouds

Ionic bond

Not sharing, stealing

Formation of Covalent Bond

Nuclei and electron clouds repel each other (repulsion) nucleus of each atoms attracts both electron clouds (attraction) molecular orbital region of high probability that is occupied by an electron as it travels through the space around to the two or more nuclei--> covalent

In electronegativity and covalent bonding of a covalent bond between two different atoms,what can be determined

The atoms are both going to have an attractions for the electrons forming the bond

Dipole

The ends of polar molecules have partial charges

Bond Energy

The energy required to break a bond between two atoms

Human Chain Demo

The energy required to break a bond between two atoms is the bond energy. The bonds that has the higher bond energy is the stronger the bond, which also have the shorter bond length.

What happens to the shared electrons in a polar covalent bond

They aren't transferred completely. Instead, it is more likely to be found near the more electronegative atom.

Usually each atom will have a different degree of attraction, what can be determined

They have different electronegativity value

Describe the change in energy and stability that takes place as a covalent bond forms.

They have low stability and become more stable when they are in a compound. Bonding causes a decrease in energy, energy is released into the surroundings.

Polar Covalent

Unequal sharing

Covalent Bond

a bond formed when atoms share one or more pairs of electrons

δ- shows _____

a partial negative charge charge

Bond Length

is the distance between two bonded atoms at their minimum potential energy

Electronegativity difference for polar covalent bond

occurs when the electronegativity values of the two atoms are not very close, if the difference is between 0.5 and 2.1, in this example, the atoms are sharing the electrons unequally, so it is a polar bond, one is holding the electrons closer to one side.

The electronegativity difference in a NONPOLAR COVALENT BOND

occurs when the electronegativity values of the two atoms are very close, less than 0.5., Thus it is assumed that the atoms are fairly equally sharing the electrons in the molecular orbital

δ+ shows a ______

partial positive charge

The symbol used to mean partial

δ

General Guidelines

•A covalent bond forms between two nonmetals. •An ionic bond forms between a nonmetal and a metal. •The type of bond that forms (metallic, ionic, or covalent) determines the properties of the substance