Introduction to Chemical Bonding

Miss Elaine MacalinaoChemistry

Using p.161-193 of the Modern Chemistry book, complete (as much as you can) the Chemical Bonding Chart given to you

If you are done, hold on to it as we will go over it afterwards

Chemical bond: a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atom together

Why form chemical bonds? Decrease potential energy Increase stability All atoms trying to achieve a stable octet

Types of chemical bonding When atoms bond, their valence electrons are

moved around in ways that make the atoms more stable

The way their valence electrons move around determine the type of bond that happens 3 major types of chemical bonds:▪ Ionic▪ Covalent▪ Metallic

Ionic Bonding

Ionic bond: chemical bonding that results from the electrical attraction between large numbers of cations and anions

Electrons are either gained or lost by an atom In doing so, both atoms

often achieve the electron configuration of the nearest noble gas

Occurs between metals losing electrons to nonmetals

Very strong bond

Ionic compound: composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal Most ionic compounds exist as

crystalline solids▪ 3D network of positive and negative

ions mutually attracted to one another▪ Ex: rocks, minerals

Ionic compounds are not composed of independent, neutral units that can be isolated and examined

IONIC

Definition Chemical bonding that results from the electrical attraction between large numbers of cations and anions

Types of atoms involved

Metals & nonmetals

Method of bond formation

Transfer of electrons

Type of structure Crystal lattice

Physical state Solid

Melting point High

Solubility in water Yes

Electrical conductivity Yes

Other properties --

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Covalent Bonding

Covalent bond: chemical bonding that results from the sharing of electron pairs between two atoms

Neither atom has an electrical charge Forces between atoms are weak Bonding between atoms of the same elements is

completely covalent

Molecule: a neutral group of atoms that are held together by covalent bonds

Molecular compound: a chemical compound whose simplest units are molecules

Diatomic molecule: a molecule containing only two atoms

COVALENT

Definition Chemical bonding that results from the sharing of electron pairs between atoms

Types of atoms involved

Nonmetals

Method of bond formation

Sharing of electrons

Type of structure Molecules

Physical state Liquid or gas

Melting point Low

Solubility in water Usually not

Electrical conductivity No

Other properties Odorous

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Metallic Bonding

Metallic bonding: the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons

Within metals, vacant orbitals allow the atoms’ outer energy levels to overlap Result = electrons become delocalized▪ Delocalized: not belonging to any one atom, but

freely move about the metal’s network of empty atomic orbitals

Metallic Properties Freedom of electrons to move in a

network of metal atoms account for the high electrical and thermal conductivity characteristic of metals

Metals can absorb a wide range of frequencies due to the many orbitals separated by extremely small energy differences they contain▪ Absorption of light results in the

excitation of metal atoms’ electrons to higher energy levels

▪ De-excitation responsible for the shiny appearance of metal surfaces

Two important properties related to characteristics of metals: Malleability: the ability of a

substance to be hammered or beaten into thin sheets

Ductility: ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire

Characteristics possible because metallic bonding is the same in all directions throughout the solid▪ One plane of atoms in a metal can slide

past another without encountering any resistance or breaking any bonds

METALLIC

Definition Chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons

Types of atoms involved

Metals

Method of bond formation

Electrons are delocalized among metal atoms

Type of structure “Sea of electrons”

Physical state Solid

Melting point Very high

Solubility in water Yes

Electrical conductivity Yes

Other properties Malleable, ductile, lustrous

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Bond Polarity

Most bonds are a blend of ionic and covalent characteristics

Difference in electronegativity determines the bond type A large difference in

electronegativity in a bond will result in ionic bonding

A small difference between two atoms will results in covalent bonding

Non-polar covalent bond: a covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge

Polar-covalent bond: a covalent bond in which the bonded atoms have an unequal attraction for shared electrons

Electronegativity

Difference

Bonding type How it looks like

0.0 – 0.3Non-polar covalent

0.4 – 1.9Polar covalent

2.0 – 3.3Ionic

Chemical Bonding Video

Essay Time!

Essay – write a 5-paragraph essay comparing and contrasting each bonding type. The

essay should incorporate the major properties from the Bonding Chart.