Combining Atoms Through Chemical Bonding Section 1 Electrons and Chemical Bonding Chapter 13 Combining Atoms Through Chemical Bonding Chemical bonding is the joining of atoms to form new substances. An interaction that holds two atoms together is called a chemical bond. When chemical bonds form, electrons are shared, gained, or lost.

Combining Atoms Through Chemical Bonding, continued Section 1 Electrons and Chemical Bonding Chapter 13 Combining Atoms Through Chemical Bonding, continued Discussing Bonding Using Theories and Models We cannot see atoms and chemical bonds with the unaided eye. So, the use of models helps people discuss the theory of how and why atoms form bonds.

Electron Number and Organization Section 1 Electrons and Chemical Bonding Chapter 13 Electron Number and Organization The number of electrons in an atom can be determined from the atomic number of the element. Electrons in an atom are organized in energy levels. The next slide shows a model of the arrangement of electron in an atom. This model and models like it are useful for counting electrons, but do not show the true structure of an atom.

Section 1 Electrons and Chemical Bonding Chapter 13

Electron Number and Organization, continued Section 1 Electrons and Chemical Bonding Chapter 13 Electron Number and Organization, continued Outer-Level Electrons and Bonding Most atoms form bond using only its valence electrons, the electrons in an atom’s outermost energy level.

Electron Number and Organization, continued Section 1 Electrons and Chemical Bonding Chapter 13 Electron Number and Organization, continued Valence Electrons and the Periodic Table You can use the periodic table to determine the number of valence electrons for atoms of some elements, as shown on the next slide.

Section 1 Electrons and Chemical Bonding Chapter 13

Chapter 13 To Bond or Not to Bond Section 1 Electrons and Chemical Bonding Chapter 13 To Bond or Not to Bond The number of electrons in the outermost energy level of an atom determine whether an atom will form bonds. Atoms that have 8 electrons in their outermost energy level do not usually form bonds. The outermost energy level is considered to be full if it contains 8 electrons.

To Bond or Not to Bond, continued Section 1 Electrons and Chemical Bonding Chapter 13 To Bond or Not to Bond, continued Filling the Outermost Level An atom that has fewer than 8 valence electrons is more likely to form bonds than at atom that has 8 valence electrons is. Atoms bond by gaining, losing, or sharing electrons to have a filled outermost energy level.

To Bond or Not to Bond, continued Section 1 Electrons and Chemical Bonding Chapter 13 To Bond or Not to Bond, continued Is Two Electrons a Full Set? Not all atoms need 8 valence electrons to have a filled outermost energy level. Helium atoms need only 2 valence electrons because the outermost level is the first energy level. Atoms of hydrogen and lithium form bonds by gaining, losing, or sharing electrons to achieve 2 electrons in the first energy level.

Chapter 13 Forming Ionic Bonds Section 2 Ionic Bonds Forming Ionic Bonds An ionic bond is a bond that forms when electrons are transferred from one atom to another atom. Charged Particles An atom is neutral because the number of electrons in an atom equals the number of protons. So, the charges cancel each other out. But when an atom gains or loses electrons, it becomes a charged particle called an ion.

Chapter 13 Forming Positive Ions Section 2 Ionic Bonds Forming Positive Ions Metal Atoms and the Loss of Electrons Atoms of most metals have few valence electrons and tend to lose these valence electrons and form positive ions. The Energy Needed to Lose Electrons Energy is needed to pull electrons away from atoms. The energy needed comes from the formation of negative ions.

Chapter 13 Forming Negative Ions Section 2 Ionic Bonds Forming Negative Ions Nonmetal Atoms Gain Electrons The outer energy level of nonmetal atoms is almost full. So, nonmetal atoms tend to gain electrons and become negative ions. The Energy of Gaining Electrons Energy is given off when nonmetals gain electrons. An ionic bond will form between a metal and a nonmetal if the nonmetal releases more energy than is needed to take electrons from the metal.

Chapter 13 Section 2 Ionic Bonds

Chapter 13 Ionic Compounds Section 2 Ionic Bonds Ionic Compounds When ionic bonds form, the number of electrons lost by the metal atoms equals the number gained by the nonmetal atoms. The ions that bond are charged, but the compound formed is neutral because the charges of the ions cancel each other.

Ionic Compounds, continued Chapter 13 Section 2 Ionic Bonds Ionic Compounds, continued When ions bond, they form a repeating three-dimensional pattern called a crystal lattice, such as the one shown below. Properties of ionic compounds include brittleness, high melting points, and high boiling points.

Chapter 13 Covalent Bonds Section 3 Covalent and Metallic Bonds Chapter 13 Covalent Bonds A covalent bond forms when atoms share one or more pairs of electrons. Substances that have covalent bonds tend to have low melting and boiling points and are brittle in the solid state. Covalent bonds usually form between atoms of nonmetals, such as the atoms shown on the next slide.

Section 3 Covalent and Metallic Bonds Chapter 13

Covalent Bonds, continued Section 3 Covalent and Metallic Bonds Chapter 13 Covalent Bonds, continued Covalent Bonds and Molecules Substances containing covalent bonds consist of particles called molecules. A molecule usually consists of two or more atoms joined in a definite ratio. The models on the next slide show two ways to represent the covalent bonds in a water molecule.

Section 3 Covalent and Metallic Bonds Chapter 13

Covalent Bonds, continued Section 3 Covalent and Metallic Bonds Chapter 13 Covalent Bonds, continued One way to represent atoms and molecules is to use electron-dot diagrams. An electron-dot diagram shows only the valence electrons in an atom.

Covalent Compounds and Molecules Section 3 Covalent and Metallic Bonds Chapter 13 Covalent Compounds and Molecules A molecule is the smallest particle into which a covalently bonded compound can be divided and still be the same compound. The Simplest Molecules are made up of two bonded atoms. Molecules made up of two atoms of the same element are called diatomic molecules.

Covalent Compounds and Molecules, continued Section 3 Covalent and Metallic Bonds Chapter 13 Covalent Compounds and Molecules, continued More-Complex Molecules Carbon atoms are the basis of many complex molecules. Each carbon atom can form four covalent bonds. These bonds can be with atoms of other elements or with other carbon atoms, as shown at right.

Chapter 13 Metallic Bonds Section 3 Covalent and Metallic Bonds Chapter 13 Metallic Bonds A metallic bond is a bond formed by the attraction between positively charged metal ions and the electrons in the metal. Movement of Electrons Throughout a Metal Bonding in metals is a result of the metal atoms being so close to one another that their outermost energy levels overlap. This overlapping allows valence electrons to move throughout the metal.

Chapter 13 Properties of Metals Section 3 Covalent and Metallic Bonds Chapter 13 Properties of Metals Conducting Electric Current Metallic bonding allows metals to conduct electric current. Electric current is conducted when valence electrons move within a metal. These electrons are free to move because the electrons are not connected to any one atom.

Properties of Metals, continued Section 3 Covalent and Metallic Bonds Chapter 13 Properties of Metals, continued Reshaping Metals Because the electrons swim freely around the metal ions, atoms in metals can be rearranged. The properties of ductility and malleability describe a metal’s ability to be reshaped. Ductility is the ability to be draw in to wires. Malleability is the ability to be hammered into sheets.

Properties of Metals, continued Section 3 Covalent and Metallic Bonds Chapter 13 Properties of Metals, continued Bending Without Breaking When a piece of metal is bent, some of the metal ions are forced closer together. But the metal does not break because the positive metal ions are always surround by and attracted to the electrons in the metal.