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Ionic, Covalent, and Metallic Bonds Visit For 100 ’ s of free powerpoints
Bond Formation The positive sodium ion and the negative chloride ion are strongly attracted to each other. How Elements Bond 2 2 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. How Elements Bond 2 2 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? How Elements Bond 2 2 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. How Elements Bond 2 2 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. How Elements Bond 2 2 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. MQQhttp://www.youtube.com/watch?v=1wpDicW_ MQQ How Elements Bond 2 2
The Convalent Bond Shared electrons are attracted to the nuclei of both atoms. How Elements Bond 2 2 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 How Elements Bond 2 2
The Convalent Bond How Elements Bond 2 2 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 chloride MgCl 2 : 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: H 2 O dihydrogen monoxide CO carbon monoxide CO 2 carbon dioxide
Prefixes to Use Mon (o) 1Oct (a)8 Di 2 Tri 3 Tetra 4 Pent(a) 5 Hex (a)6 Hept (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 O CH 3 COOH: H-C-C-O-H H CH 4 :H-C-H H
4 Molecules of Life Lipids Carbohydrates Protein Nucleic Acids
Carbohydrates Can be simple (sugar) or complex (starch) Used for energy
Protein Found everywhere in everything Made 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 nature An emperical formula is the lowest whole number formula for a molecule For the emperical formula CH C 2 H 2 acetylene C 6 H 6 benzene