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Ionic and Covalent Compounds Ions and molecules can combine to form compounds. Because there are millions of compounds, scientists organize them into groups. One way compounds are grouped is by the kind of chemical bond they have. A chemical bond is the combining of atoms to form molecules or compounds.

Ionic and Covalent CompoundsIonic and Covalent Compounds Bonding can occur between the valence electrons of different atoms. The behavior of valence electrons determines if an ionic compound or a covalent compound is formed.Bonding can occur between the valence electrons of different atoms. The behavior of valence electrons determines if an ionic compound or a covalent compound is formed.

Ionic Compounds and Their PropertiesIonic Compounds and Their Properties The properties of ionic compounds are a result of strong attractive forces called ionic bonds. An ionic bond is an attraction between oppositely charged ions. The compounds that contain ionic bonds are called ionic compounds.The properties of ionic compounds are a result of strong attractive forces called ionic bonds. An ionic bond is an attraction between oppositely charged ions. The compounds that contain ionic bonds are called ionic compounds.

Ionic Compounds and Their PropertiesIonic Compounds and Their Properties Ionic compounds can be formed by the reaction of a metal with a nonmetal. Metal atoms become positively charged ions and the nonmetal atoms become negatively charged ion when the electron is transferred. Sodium chloride, table salt, is an ionic compound.Ionic compounds can be formed by the reaction of a metal with a nonmetal. Metal atoms become positively charged ions and the nonmetal atoms become negatively charged ion when the electron is transferred. Sodium chloride, table salt, is an ionic compound.

Ionic Compounds PropertiesIonic Compounds Properties Brittleness - Ionic compounds tend to be brittle solids at room temperature, so they usually break apart when hit. High Melting Points - Strong ionic bonds have high melting points. This is why most ionic compounds are solids at room temperature. Solubility and Electrical Conductivity - Many ionic compounds are highly soluble and dissolve easily in water. The solution that forms when an ionic compound dissolves in water can conduct an electric current because the ions are charged and are able to move freely past each other.Brittleness - Ionic compounds tend to be brittle solids at room temperature, so they usually break apart when hit. High Melting Points - Strong ionic bonds have high melting points. This is why most ionic compounds are solids at room temperature. Solubility and Electrical Conductivity - Many ionic compounds are highly soluble and dissolve easily in water. The solution that forms when an ionic compound dissolves in water can conduct an electric current because the ions are charged and are able to move freely past each other.

Covalent Compounds and Their Properties Most compounds are covalent compounds. Covalent compounds are compounds that form when a group of atoms shares electrons. The group of atoms that make up a covalent compound is called a molecule.Most compounds are covalent compounds. Covalent compounds are compounds that form when a group of atoms shares electrons. The group of atoms that make up a covalent compound is called a molecule.

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

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

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

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

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

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

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

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

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

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

Proteins are biochemicals composed of “ building blocks ” called amino acids. Amino acids are small molecules made up of carbon, hydrogen, oxygen, and nitrogen atoms, and sometimes sulfur atoms.Proteins are biochemicals composed of “ building blocks ” called amino acids. Amino acids are small molecules made up of carbon, hydrogen, oxygen, and nitrogen atoms, and sometimes sulfur atoms.

Most of the biochemicals found in living things are proteins. Proteins function in the body to regulate chemical activities, transport and store materials, build and repair body structures, and regulate processes.Most of the biochemicals found in living things are proteins. Proteins function in the body to regulate chemical activities, transport and store materials, build and repair body structures, and regulate processes.

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

There are only five kinds of nucleotides, but nucleic acids may have millions of nucleotides bonded together.There are only five kinds of nucleotides, but nucleic acids may have millions of nucleotides bonded together.

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

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