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Ionic and Covalent CompoundsIonic and Covalent Compounds

Ions and molecules can combine to form Ions and molecules can combine to form compounds. Because there are millions compounds. Because there are millions of compounds, scientists organize them of compounds, scientists organize them into groups. into groups. One way compounds are One way compounds are

grouped is by the kind of chemical bond grouped is by the kind of chemical bond they have.they have. A A chemicalchemical bondbond is the is the

combining of atoms to form molecules combining of atoms to form molecules or compounds.or compounds.

• Ionic and Covalent Ionic and Covalent CompoundsCompounds

• Bonding can occur between the Bonding can occur between the valencevalence electrons of different electrons of different atoms.atoms. The behavior of valence The behavior of valence electrons determines if an electrons determines if an ionicionic compound or a compound or a covalentcovalent compound is formed.compound is formed.

• Ionic Compounds and Their Ionic Compounds and Their PropertiesProperties

• The properties of ionic compounds The properties of ionic compounds are a result of are a result of strongstrong attractive attractive forces called ionic bonds. An forces called ionic bonds. An ionic ionic bondbond is an attraction between is an attraction between oppositelyoppositely charged ions. charged ions. The The compounds that contain ionic compounds that contain ionic bonds are called bonds are called ionic compounds.ionic compounds.

• Ionic Compounds and Their Ionic Compounds and Their PropertiesProperties

• Ionic compounds can be formed by Ionic compounds can be formed by the reaction of a the reaction of a metalmetal with a with a nonmetalnonmetal. Metal atoms become . Metal atoms become positively charged ions and the positively charged ions and the nonmetal atoms become negatively nonmetal atoms become negatively charged ion when the electron is charged ion when the electron is transferredtransferred. Sodium chloride, . Sodium chloride, table salt,table salt, is an ionic compound. is an ionic compound.

• Ionic Compounds PropertiesIonic Compounds Properties• BrittlenessBrittleness - Ionic compounds tend to be - Ionic compounds tend to be

brittle solids at room temperature, so they brittle solids at room temperature, so they usually break apart when hit. usually break apart when hit. HighHigh Melting Melting PointsPoints - Strong ionic bonds have high - Strong ionic bonds have high melting points. This is why most ionic melting points. This is why most ionic compounds are solids at room temperature. compounds are solids at room temperature. SolubilitySolubility andand Electrical Electrical ConductivityConductivity - - Many ionic compounds are highly soluble Many ionic compounds are highly soluble and dissolve easily in water. The solution and dissolve easily in water. The solution that forms when an ionic compound that forms when an ionic compound dissolves in water can conduct an electric dissolves in water can conduct an electric current because the ions are charged and are current because the ions are charged and are able to move freely past each other.able to move freely past each other.

• Covalent Compounds and Their Properties

• Most compounds are covalent Most compounds are covalent compounds. compounds. Covalent compoundsCovalent compounds are are compounds that form when a group of compounds that form when a group of atoms atoms sharesshares electrons. electrons. The group of The group of atoms that make up a covalent atoms that make up a covalent compound is called a molecule.compound is called a molecule.

• Covalent Compounds Properties• LowLow Solubility Solubility Most covalent compounds are not Most covalent compounds are not

soluble in water. soluble in water. LowLow Melting Points Melting Points The forces of The forces of attraction between molecules of covalent compounds attraction between molecules of covalent compounds are much weaker than the bonds holding ionic solids are much weaker than the bonds holding ionic solids together, so less heat is needed to separate the together, so less heat is needed to separate the molecules of covalent compounds. molecules of covalent compounds. Low Low ElectricalElectrical ConductivityConductivity Although most covalent compounds do Although most covalent compounds do not dissolve in water, some do.not dissolve in water, some do. Most of the covalent Most of the covalent compounds that dissolve in water form solutions that compounds that dissolve in water form solutions that have uncharged molecules. Some covalent compounds have uncharged molecules. Some covalent compounds do form ions when they dissolve in water. do form ions when they dissolve in water. Many acids, Many acids, for example, form ions in water and these solutions do for example, form ions in water and these solutions do conduct electricity.conduct electricity.

•Organic compounds Organic compounds are covalent are covalent compounds composed compounds composed of carbon-based of carbon-based moleculesmolecules. More than . More than 90%90% of all compounds of all compounds belong to this group.belong to this group.

•All organic compounds All organic compounds contain carbon.contain carbon. Each Each carbon atom has carbon atom has fourfour valence electrons so valence electrons so each carbon atom can each carbon atom can make four make four bondsbonds with with four other atoms.four other atoms.

•Organic compounds Organic compounds may also contain may also contain hydrogen,hydrogen, oxygen, oxygen, sulfursulfur, nitrogen, and , nitrogen, and phosphorus.phosphorus.

•Carbon atoms bond Carbon atoms bond together to form a together to form a structure called a structure called a backbone.backbone. It makes It makes the molecule very the molecule very strong. strong. There are There are threethree types of structures for types of structures for organic compounds.organic compounds.

• Many organic compounds Many organic compounds contain several kinds of atoms, contain several kinds of atoms, but some contain only but some contain only twotwo. . Organic compounds that Organic compounds that contain only carbon and contain only carbon and hydrogen are called hydrogen are called hydrocarbons.hydrocarbons.

•Organic compounds Organic compounds made by living things made by living things are called are called biochemicalsbiochemicals. . Biochemicals are Biochemicals are divided into four divided into four categories: categories: carbohydrates, lipids, carbohydrates, lipids, proteins, and nucleic proteins, and nucleic acids.acids.

•CarbohydratesCarbohydrates are are biochemicals composed biochemicals composed of one or more simple of one or more simple sugar molecules bonded sugar molecules bonded together. together. Carbohydrates are used Carbohydrates are used as a source of energy.as a source of energy.

•LipidsLipids are are biochemicals that do biochemicals that do not dissolve in water. not dissolve in water. Fats, oils, and waxes Fats, oils, and waxes are kinds of lipids. are kinds of lipids. Lipids are also used to Lipids are also used to store some vitamins.store some vitamins.

•Lipids store excess Lipids store excess energyenergy in the body. in the body. When an organism has When an organism has used up most of its used up most of its carbohydrates, it can carbohydrates, it can obtain energy by obtain energy by breaking down lipids.breaking down lipids.

•ProteinsProteins are are biochemicals composed biochemicals composed of “building blocks” of “building blocks” called called aminoamino acids. acids. Amino acids are Amino acids are smallsmall molecules made up of molecules made up of carbon, hydrogen, carbon, hydrogen, oxygen, and nitrogen oxygen, and nitrogen atoms, and sometimes atoms, and sometimes sulfur atoms.sulfur atoms.

•Most of the biochemicals Most of the biochemicals found in living things are found in living things are proteins.proteins. ProteinsProteins function in the body to function in the body to regulate chemical regulate chemical activities, activities, transporttransport and and storestore materials, build materials, build and repair body and repair body structures, and regulate structures, and regulate processes.processes.

•NucleicNucleic Acids Acids •The largest molecules The largest molecules

made by living organisms made by living organisms are nucleic acids.are nucleic acids. Nucleic Nucleic acids are bio-chemicals acids are bio-chemicals made up of made up of nucleotidesnucleotides. . Nucleotides are molecules Nucleotides are molecules made of carbon, hydrogen, made of carbon, hydrogen, oxygen, nitrogen, and oxygen, nitrogen, and phosphorus atoms.phosphorus atoms.

•There are only There are only fivefive kinds of nucleotides, kinds of nucleotides, but nucleic acids may but nucleic acids may have have millionsmillions of of nucleotides bonded nucleotides bonded together.together.

•Nucleic acids have Nucleic acids have several functions. One several functions. One function is to store function is to store geneticgenetic information. information. They also help build They also help build proteins and other proteins and other nucleic acids.nucleic acids.

•Nucleic acids are Nucleic acids are sometimes called the sometimes called the blueprintsblueprints of life, of life, because they contain because they contain all the information all the information needed for a cell to needed for a cell to make all its proteins.make all its proteins.

• DNA and RNA There are two kinds of nucleic acids: DNA and RNA.

• DNA (deoxyribonucleic acid) is the genetic material of the cell. DNA molecules can store a huge amount of information -- DNA molecules in a single human cell have a length of about 2 m.