Covalent bonds Pg 165-169. Covalent Bonds G Nonmetals with high ionization energies do not tend to form ionic bonds (transfer of electrons) G Instead

Covalent bondsCovalent bonds

Pg 165-169Pg 165-169

Covalent BondsCovalent Bonds

Nonmetals with high ionization energies do not tend to form ionic bonds (transfer of electrons)

Instead of transferring electrons they share them

Nonmetals with high ionization energies do not tend to form ionic bonds (transfer of electrons)

Instead of transferring electrons they share them

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Sharing ElectronsSharing ElectronsTwo atoms of hydrogen can share their electrons to achieve a stable electron configuration.

Covalent Bond - a chemical bond in which two atoms share a pair of valence electrons

Two atoms of hydrogen can share their electrons to achieve a stable electron configuration.

Covalent Bond - a chemical bond in which two atoms share a pair of valence electrons



Molecular ModelsMolecular Models

The electron cloud model and space-filling model show that orbitals of atoms overlap when a covalent bond forms

The electron cloud model and space-filling model show that orbitals of atoms overlap when a covalent bond forms





Molecules of elementsMolecules of elementsMolecule - a neutral group of atoms that are joined together by one or more covalent bonds

They are neutral because the number of protons and electrons are balanced in the shared molecule

The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond

Molecule - a neutral group of atoms that are joined together by one or more covalent bonds

They are neutral because the number of protons and electrons are balanced in the shared molecule

The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond





Molecules of elementsMolecules of elements

Many nonmetal elements exist as diatomic molecules

Diatomic means “two atoms”

Many nonmetal elements exist as diatomic molecules

Diatomic means “two atoms”





Multiple Covalent Bonds

Multiple Covalent BondsA Nitrogen molecule (N2) shares three pairs

of electrons, each atom then has eight valence electrons

Each pair of shared electrons is represented by a long dash in the structural formula

When two atoms share three pairs of electrons it is called a triple bond

When two atoms share two pairs of electrons it is called a double bond

A Nitrogen molecule (N2) shares three pairs of electrons, each atom then has eight valence electrons

Each pair of shared electrons is represented by a long dash in the structural formula

When two atoms share three pairs of electrons it is called a triple bond

When two atoms share two pairs of electrons it is called a double bond



Unequal Sharing of Electrons

Unequal Sharing of Electrons

In general, elements on the right of the periodic table have a greater attraction for electrons than elements on the left (except noble gases)

And elements at the top of a group have a greater attraction for electrons than elements at the bottom of a group

In general, elements on the right of the periodic table have a greater attraction for electrons than elements on the left (except noble gases)

And elements at the top of a group have a greater attraction for electrons than elements at the bottom of a group



Polar Covalent BondsPolar Covalent BondsWhen hydrogen and chlorine form a covalent bond the chlorine atom has a greater attraction for the electrons than the hydrogen atom

In the hydrogen chloride molecule, the shared electrons spend more time near the chlorine atom than near the hydrogen atom

Polar covalent bond- a covalent bond in which electrons are not shared equally

When atoms form a polar covalent bond, the atom with the greater attraction for electrons has a partial negative charge. The other atom has a partial positive charge

When hydrogen and chlorine form a covalent bond the chlorine atom has a greater attraction for the electrons than the hydrogen atom

In the hydrogen chloride molecule, the shared electrons spend more time near the chlorine atom than near the hydrogen atom

Polar covalent bond- a covalent bond in which electrons are not shared equally

When atoms form a polar covalent bond, the atom with the greater attraction for electrons has a partial negative charge. The other atom has a partial positive charge

Hydrogen chlorideHydrogen chloride





Polar and Nonpolar Molecules

Polar and Nonpolar MoleculesIf a molecule with a polar covalent bond

contains only two atoms, it will be polar

But when molecules have more than two atoms, the answer is not as obvious

The type of atoms in a molecule and its shape are factors that determine whether a molecule is polar or nonpolar

If a molecule with a polar covalent bond contains only two atoms, it will be polar

But when molecules have more than two atoms, the answer is not as obvious

The type of atoms in a molecule and its shape are factors that determine whether a molecule is polar or nonpolar



PolarPolar

NonpolarNonpolar

Carbon dioxide (CO2)Carbon dioxide (CO2)

Each double bond in carbon dioxide is polar because oxygen has a grater attraction for electrons than the carbon atom

Because the molecule is linear (all three atoms line up in a row) the pull of the charges cancel out and the molecule as a whole is nonpolar

Each double bond in carbon dioxide is polar because oxygen has a grater attraction for electrons than the carbon atom

Because the molecule is linear (all three atoms line up in a row) the pull of the charges cancel out and the molecule as a whole is nonpolar





Water (H20)Water (H20)Water molecule has two single bonds which are polar because oxygen has a greater attraction for electrons that hydrogen

The water molecule has a bent shape so the polar bonds do not cancel out

The two hydrogen atoms are located on the same side of the molecule opposite the oxygen atom

The oxygen side has a partial negative charge and the hydrogen side has a partial positive charge

Water molecule has two single bonds which are polar because oxygen has a greater attraction for electrons that hydrogen

The water molecule has a bent shape so the polar bonds do not cancel out

The two hydrogen atoms are located on the same side of the molecule opposite the oxygen atom

The oxygen side has a partial negative charge and the hydrogen side has a partial positive charge


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Attraction Between Molecules

Attraction Between Molecules

Attractions between polar molecules are stronger than attractions between nonpolar molecules

Water boils at 1000C and Methane boils at -161.50C even if they are very similar in mass

Because water molecules are polar, the attractions between the molecules are stronger than the attractions between the nonpolar methane molecules

Attractions between nonpolar molecules exist but they are just weaker

Attractions among nonpolar molecules explain why nitrogen can be stored as a liquid at low temperatures and high pressures.

Attractions between polar molecules are stronger than attractions between nonpolar molecules

Water boils at 1000C and Methane boils at -161.50C even if they are very similar in mass

Because water molecules are polar, the attractions between the molecules are stronger than the attractions between the nonpolar methane molecules

Attractions between nonpolar molecules exist but they are just weaker

Attractions among nonpolar molecules explain why nitrogen can be stored as a liquid at low temperatures and high pressures.

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Covalent bonds Pg 165-169. Covalent Bonds G Nonmetals with high ionization energies do not tend to form ionic bonds (transfer of electrons) G Instead