Ionic and Covalent Compounds

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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.

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• Ionic 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.

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• Ionic 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.

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• Ionic 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.

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• Ionic 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.

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• 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.

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• 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.
• 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.

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

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

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

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• 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.

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

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

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

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• 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.

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• 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.

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• 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.

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• 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.

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• Nucleic 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.

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

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

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

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• 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.