Ch. 6 Bonding

Section 4: Metallic Bonding

Bonding of Metals

• the highest energy level for most metal atoms only contains s electrons.

• usually have empty p and d blocks • these vacant overlapping orbitals

allow outer electrons to roam freely around the entire outer electron cloud

• the electrons are delocalized – are not with one specific atom

Bonding of Metals

• these roaming electrons form a sea of electrons around the metal atoms

• metal nuclei are packed in a crystal lattice (like ionic compounds)

• metallic bonding – bonding that results from the attraction between metal nuclei and sea of electrons

Properties of Metals

• conductive (heat, electricity, sound)– caused by the freedom of electrons to move

around the atoms (electrons can carry the message)

• luster (shininess)– contain many orbitals with only small

differences in energy– remember the photoelectric effect? – Because of the tons of orbitals at similar

energy levels, many different frequencies of light are capable of making metal shine

Properties of Metals• malleable and ductile–moveable electrons enable metal nuclei

to slide past each other if hit or pulled (like ball bearings)

Bond Strength

• depends on the nuclear charge (how many protons)

• depends on the number of electrons in the “sea”

• More protons &/or electrons = stronger bond

• Measured using the heat of sublimination – amount of heat required to turn solid, bonded metal atoms into gaseous individual atoms

Comparison of Bond Types• All bonds are considered to be “strong”– metallic bonds are strong and flexible making

them useful in the real world– ionic bonds connect ALL ions together tightly,

so there is no flexiility. Ionic compounds are most useful in solutions (more on that MUCH later)

– molecules (covalent bonds) are more easily pulled apart because the attraction btwn molecules (intermolecular force) is weak. The attraction within molecules (intramolecular force) is very strong.

Comparison of Bond Types Ionic Compounds:

higher melting and boiling pointsall are solid at room temperature hard: Because of the strong connecting bonds, it is

difficult for one layer of ions to move past anotherbrittle: if one layer is moved, the layers come

apart completely

Comparison of Bond TypesMetallic Compounds:

high melting and boiling pointsall but Hg are solid at room temperature hard: Because of the strong attractions btwn

nuclei & sea of electrons, metals are very toughflexible: if one layer is moved, the other layers can

slide over the sea of electrons and the whole sample can change shape.

Comparison of Bond Types

Metallic Compounds: great conductors in solid & liquid states because of the mobile

electrons. Ionic Compounds:

good conductors in liquid state because ions are free to move and carry charge

poor conductor in solid statebecause ions are fixed in place

good conductors when in solution b/c ions can move around in water Molecular compounds:

poor conductors in any state because there are no ions