Ionic and Covalent Bonding

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Bonding• Atoms with unfilled valence shells are

considered unstable.

• Atoms will try to fill their outer shells by bonding with other atoms.

• The number of valence electrons will determine how many bonds the atom can form.

• Two types of bonds we will discuss:– Ionic bonds– Covalent bonds 2

Ions Review• Ions are charged atoms (positive or negative).

• Ions are formed when atoms gain or lose electrons.

• Positive ions are called cations.– Formed when the atom loses electrons.

• Negative ions are call anions.– Formed when the atom gains electrons.

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Ionic Bonds

• Ionic bonds are formed between metals and non-metals.

• Ionic bonds are formed between oppositely charged atoms (ions).

• Ionic bonds are formed by the transfer of electrons.– One atom donates electrons to the other.

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Ionic Bonds (continued)• In an ionic bond one atom will lose its electron(s)

and the other will gain them.– Depends on the number of valence electrons.

• The transfer of electrons creates a positive ion and a negative ion.

• The opposite charges attract one another, causing a bond to form.

Bonding Animation 5

Drawing Ionic Bonds• We can illustrate ionic bonding using

Lewis structures.

• 1 – Draw the Lewis structure for each element.– Ex: Na Cl

• 2 – Draw arrows to show the gain/loss of electrons

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Drawing Ionic Bonds (continued)

• 3 – Draw ion Lewis diagrams showing the new charge for each ion.– Ex:

• The chemical formula for the compound formed represents the ratio of negative ions to positive ions.– Ex: NaCl – for every 1 sodium ion, there is

also 1 chlorine ion.

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Practice Drawing Ionic Bonds

Elements Lewis Ion Lewis Formula

Diagram Diagram

Calcium

Sulfur

Magnesium

Bromine

Aluminum

Oxygen8

Covalent Bonds

• Covalent bonds form between two non-metals.

• Covalent bonds are formed when atoms share electrons.– Both atoms need to gain electrons, so they

share the electrons they have.

• Atoms can share more than one pair of electrons to create double and triple bonds.

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Covalent Bonds (continued)• Atoms can share their electrons equally or unequally.

• When atoms share electrons equally it is called a non-polar bond.– Non-polar covalent bonds form between atoms of the same type. Ex:

H2

• When atoms share electrons unequally it is called a polar covalent bond.– One atom pulls the electrons closer to itself.– The atom that pulls the electrons more gets a slightly negative

charge.– The other atom gets a slightly positive charge.

• Ex: Water molecule

Bonding Animation 10

Drawing Covalent Bonds• We can illustrate covalent bonding using

Lewis structures.• 1 – Draw a Lewis structure for each element.

– Ex: C H

• 2 – Draw circles around the shared pair(s) of electrons.– Ex:

• 3 - Continue adding atoms until all atoms have a full valence shell.– Ex:

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Practice Drawing Covalent Bonds

Elements LewisFormula

Diagram

Hydrogen

Hydrogen

Carbon

Oxygen13

Ionic Vs. Covalent Bonds

Ionic Bonds• Form when electrons

are exchanged between atoms.

• Form between a metal and a non-metal.

Covalent Bonds• Form when electrons

are shared between atoms.

• Form between two non-metals.

Both types of bonds result in all atoms having a full outer energy level.

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