Chapter 19 Chemical Bonding

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Chapter 19Chemical Bonding

• Types of Chemical Bonds

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Three Types of Chemical Bonds

• Ionic Bonds
• Covalent Bonds
• Metallic Bonds

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Lets Review!

• Chemical Bonding

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What is Chemical Bonding

• Chemical bonding is the joining of atoms to form
  new substances. Therefore, a chemical bond is a
  force of attraction that holds two atoms together.

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Remember

• Atoms are made of protons, neutrons, and
  electrons.
• Protons have a positive charge.
• Neutrons have no charge.
• Electrons have a negative charge.

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Atoms Have Energy Levels

• The center of the atoms where the protons and
  neutrons are located is called the nucleus.
• The electrons are located in energy levels around
  the nucleus.

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Energy Levels

• The first energy level, closest to the nucleus,
  can hold up to 2 electrons.
• All other energy levels can hold up to 8
  electrons.
• The outer most energy level holds the atoms
  valence electrons.

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Back to Bonding!
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Ionic Bonds

• An ionic bond is the force of attraction between
  oppositely charged ions.
• Ions are charged particles that form during
  chemical changes when one or more valence
  electrons transfer from one atom to another.

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Positive Ions

• Atoms that lose an electron become positively
  charged because they have more protons than
  electrons.
• Atoms that become positively charged are atoms
  that have few valence electrons.
• Positive ions tend to be formed by metals.

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Negative Ions

• Negative ions are formed when an atom gains an
  electron.
• Atoms that gain electrons to fill their outer
  level already have many electrons in the outer
  level.
• Negative ions tend to be nonmetals.

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Charged Ions Form Neutral Compounds

• When a metal reacts with a nonmetal, the same
  number of electrons is lost by the metal atom as
  is gained by the nonmetal atom. Because the
  atoms have opposite charges, the compound formed
  is neutral. This is an example of electrostatic
  attraction in which opposite electric charges
  stick together. (static cling)

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Ions Bond to Form a Crystal Lattice

• The ions that make up an ionic compound are
  bonded in a repeating three-dimensional pattern
  called a crystal lattice. The ions are arranged
  as alternating positives and negatives.

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Properties of Ionic Compounds

• High melting point
• High boiling point
• Brittle at room temperature
• Usually break apart when hit with a hammer

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Covalent Bonds

• Covalent bonds are formed between two atoms that
  are both nonmetals.
• In a covalent bond, the two atoms share electrons
  instead of gaining or losing electrons like in
  ionic bonding.
• A covalent bond is the force of attraction
  between the nuclei of atoms and the electrons
  shared by the atoms.

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Covalently Bonded Atoms Form Molecules

• Covalent compounds consist of individual
  particles called molecules.
• A molecule is a neutral group of atoms held
  together by covalent bonds.

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Diatomic Molecules

• A diatomic molecule is a molecule that consists
  of two atoms covalently bonded.
• Some elements are called diatomic because they
  occur in nature as diatomic molecules composed of
  two atoms of the element. These include
  hydrogen, oxygen, nitrogen, fluorine, chlorine,
  bromine, and iodine.

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Metallic Bonds

• A metallic bond is the force of attraction
  between a positively charged metal ion and the
  electrons in the metal.
• The metal atoms get so close together that their
  outermost energy levels overlap, allowing
  electrons to move from one atom to another.

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Dont Forget

• Metal are good conductors of electric current.
• Metals are malleable.
• Metals are ductile.
• Metals can bend without breaking.