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¡ 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
8 valence electrons; full energy level stability (like the noble gases!)
¡ 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 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
¡ Occurs between metals losing electrons to nonmetals
¡ Very strong bond
What is an ion?
¡ 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
IONICDefinition Chemical bonding that results from the electrical
attraction between large numbers of cations and anions
Types of atoms involved Metals & nonmetalsMethod of bond formation Transfer of electronsType of structure Crystal latticePhysical state SolidMelting point HighSolubility in water YesElectrical conductivity YesOther properties --Image
¡ 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
COVALENTDefinition Chemical bonding that results from the sharing of
electron pairs between atomsTypes of atoms involved NonmetalsMethod of bond formation Sharing of electronsType of structure MoleculesPhysical state Liquid or gasMelting point LowSolubility in water Usually notElectrical conductivity NoOther properties OdorousImage
¡ 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 & allow outer electrons to move freely throughout the metal§ Result = electrons become delocalized
▪ Delocalized: valence electrons do not belong to any one atom
¡ Metallic Properties§ High electrical and heat conductivity due to the freedom of
electrons to move in a network of metals§ De-excitation responsible for the shiny appearance of metal
surfaces
What are some properties of metals you can think of?
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
METALLICDefinition Chemical bonding that results from the attraction
between metal atoms and the surrounding sea of electrons
Types of atoms involved MetalsMethod of bond formation Electrons are delocalized among metal atomsType of structure “Sea of electrons”Physical state SolidMelting point Very highSolubility in water YesElectrical conductivity YesOther properties Malleable, ductile, lustrous Image
¡ 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
