Ionic, Covalent, and Metallic Bonds

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Bond Formation

• The positive sodium ion and the negative chloride ion are strongly attracted to each other.

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• This attraction, which holds the ions close together, is a type of chemical bond called an ionic bond.

• The compound formed this way is called a salt

Bond Formation• The compound sodium chloride, or table

salt, is formed.

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• A compound is a pure substance containing two or more elements that are chemically bonded.

More Gains and Losses• Can elements lose

or gain more than one electron?

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• The element magnesium, Mg, in Group 2 has two electrons in its outer energy level. • Magnesium can lose these two electrons and achieve a completed energy level.

More Gains and Losses

• Some atoms, such as oxygen, need to gain two electrons to achieve stability.

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• The two electrons released by one magnesium atom could be gained by a single atom of oxygen.

• When this happens, magnesium oxide (MgO) is formed.

Convalent Bonds—Sharing

• Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult.

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• The alternative is sharing electrons.

The Convalent Bond• The chemical bond that forms between

nonmetal atoms when they share electrons is called a covalent bond.

• http://www.youtube.com/watch?v=1wpDicW_MQQ

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The Convalent Bond

• Shared electrons are attracted to the nuclei of both atoms.

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• They move back and forth between the outer energy levels of each atom in the covalent bond.

• So, each atom has a stable outer energy level some of the time.

The Convalent Bond• The neutral particle is formed when atoms

share electrons is called a molecule

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The Convalent Bond

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• A molecule is the basic unit of a molecular compound.

Naming Covalent Compounds

Remember that ionic compounds are named by saying the name of the first element and then the second element with the ending changed to “ide”:NaCl: sodium chlorideMgCl2: magnesium chloride

Naming Covalent Compounds

Covalent Compounds are also named by stating the name of the first element and then the second changed to “ide”.However, as the elements share electrons and are not charged, we must use prefixes to tell the number of each element in the compound.Ex: H2O dihydrogen monoxideCO carbon monoxideCO2 carbon dioxide

Prefixes to Use

Mon (o) 1 Oct (a) 8Di 2Tri 3Tetra 4Pent(a) 5Hex (a) 6Hept (a) 7

Hydrocarbons

Hydrocarbons are covalently bonded molecules with the elements C and H.

Hydrocarbons are organic molecules because they have chains of carbons

Petroleum compounds are hydrocarbons. Wait, so petroleum and plastics are organic? Yes, by the chemical definition they are.

Carbon Forms Chains

Each carbon has 4 valence electrons and so can form 4 bonds

H OCH3COOH: H-C-C-O-H

H H

CH4: H-C-HH

4 Molecules of Life

LipidsCarbohydratesProteinNucleic Acids

Lipid

FAT!!

Carbohydrates

Can be simple (sugar) or complex (starch)Used for energy

Protein

Found everywhere in everythingMade by the DNA/RNA of cell

Nucleic Acid

Found in DNA and RNA

Molelcular vs Emperical Formulas

A molecular formula is the formula as we find it in natureAn emperical formula is the lowest whole number formula for a moleculeFor the emperical formula CHC2H2 acetylene

C6H6 benzene