Chapter 2: Atoms and Bonding Chemical Interactions Chapter 2: Atoms and Bonding

Inside the Atom Describe the structure of an atom and define protons, neutrons, and electrons. Explain the role of valence electrons in forming chemical bonds. Terms: nucleus, protons, neutrons, electrons, valence electrons, electron dot diagram

Inside the Atom Structure of an Atom Atom made of nucleus surrounded by one or more electrons Proton—positively charged Neutron—neutral/no charge Electron—negatively charged

Inside the Atom Structure of an Atom

Inside the Atom Electrons in Atoms Electrons are in an electron cloud around the nucleus Little Particles, Big Spaces Protons and neutrons make up most of the mass of an atom Electrons make up most of the volume of the atom Valence Electrons Outer most electrons Determines properties and bonding of an atom

Inside the Atom Models Dalton—solid ball Thomson—plum pudding model Rutherford—electrons orbit around the nucleus Bohr—electrons are in shells around the nucleus Current model—nucleus surrounded by electron clouds

Inside the Atom Lewis-dot Diagram Dots represent valence electrons

Inside the Atom Why Atoms form Bonds Atoms are more chemically stable with 8 valence electrons Atoms gain or lose electrons in order to become chemically stable Electrons can be given, accepted, or shared When atoms interact new substance are formed

Atoms in the Periodic Table Periodic Table: organized elements by increasing atomic number Atomic Number: number of protons Group/Family: vertical column on table Have similar characteristics Have same valence electrons Period: horizontal row on table

Atoms in the Periodic Table Periodic Table: organized elements by increasing atomic number Atomic Number: number of protons Group/Family: vertical column on table Have similar characteristics Have same valence electrons Period: horizontal row on table

Atoms in the Periodic Table Noble Gases Group 18—inactive atoms Reactive Nonmetals Group 17-Halogens Very reactive—need 1 electron Reactive Metals Group 1-Alkali Metals Most reactive metals—give up 1 electron

Atoms in the Periodic Table

Atoms in the Periodic Table

Ionic Bonding Electron Transfer Elements gain or lose electrons as they strive to have eight valence electrons When an atom loses an electron—it becomes positive When an atom gains an electron—it becomes negative Ion: atom with a charge

Ionic Bonding Forming an Ionic Bond Ionic Bond: attraction between two oppositely charged ions

Ionic Bonding Polyatomic Ions Naming Ionic Compounds Ions made of more than one atom Naming Ionic Compounds Name of positive ion then name of negative ion End of name –ide For example: Sodium Chloride

Ionic Bonding Properties of Ionic Compounds All have crystal shape, high melting points, and can conduct electricity Formed between metals and nonmetals Crystal Shape 3-D arrangements of ions called crystals Ions are attracted to opposite charges and line up in rows High Melting Points Ionic bonds are strong and takes high energy/heat to break Solid at room temperatures Electrical Conductivity Ions break up when dissolved in a liquid Moving particles conduct electricity

Covalent Bonds Electron Sharing Formed when two atoms share electrons Form between two or more nonmetals Both atoms attract the two shared electrons at the same time

Covalent Bonds How Many Bonds? Properties of Molecular Compounds Double Bond: form when two pairs of electrons are shared Properties of Molecular Compounds Created with covalent bonds Lower melting points than ionic bonds Most poor conductors of electricity