The simplest form of matter is an element. The smallest particle of an element is an atom. Some elements like to combine, or bond, to form compounds in fixed proportions. For example NaCl and H 2 O are compounds. Each compound has properties that are different than those of the elements they are composed of. For an element, the tendency to bond or form an ion is determined by the number of electrons in its outermost shell called the valence shell. Bohr diagrams focus on the valence electrons. Compounds, Atoms, and Ions 7.1 VOCABULARY bond valence shell valence electron ion

Atoms tend to acquire the same number of valence electrons as their nearest noble gas. Noble gases have complete valence shells. An atom and an ion of the same element have completely different properties, such as size. For example the Na atom is larger than the Na + ion. Compounds, Atoms, and Ions 7.1 VOCABULARY bond valence shell valence electron ion

Chemical Bonding 7.2 VOCABULARY chemical bonds ionic compounds ionic bonding covalent molecular compounds covalent bonding molecule diatomic molecules phases states A chemical bond is a force that holds atoms together to form compounds. There are two general types of bonds: ionic and covalent. Ionic bonds involve a transfer of electrons between atoms. Ionic bonding forms ionic compounds. For example CaF 2 Covalent bonds involve a sharing of electrons between atoms. The basic unit of a covalently bonded compound is a molecule. Covalent bonds form molecular compounds. For example O 2

Chemical Bonding 7.2 VOCABULARY chemical bonds ionic compounds ionic bonding covalent molecular compounds covalent bonding molecule diatomic molecules phases states Ionic compounds separate into ions when dissolved in water and can conduct electricity, while covalent compounds do not separate into ions, nor do they conduct electricity.

Ionic Compounds: Chemical Formulas and Naming 7.3 VOCABULARY chemical formula ion charge balance multivalent polyatomic ions A chemical formula describes the proportions of the component elements. The chemical formulas for ionic compounds can be predicted by balancing ion charges. The fundamental rule for determining the chemical formula for any ionic compound is that the total ion charge for the compound is zero. The chemical names are derived from the ion names. For example:NaCl = sodium chloride K 2 O = potassium oxide Ionic compounds can be divided into three types: binary ionic compounds ionic compounds with multivalent elements ionic compounds with polyatomic ions

Molecular Compounds: Chemical Formulas and Naming 7.4 Molecular compounds result when atoms of non-metals share electrons to bond. The chemical formulas for molecular compounds are derived from their chemical names (and vice versa) based on a prefix system. Charge balancing is not required for molecular compounds.

Compounds, Ions, and Molecules Compounds result when elements bond together in fixed proportions. Bohr diagrams can illustrate how ions form by focusing on the atom’s electrons. Atoms tend to acquire the same number of valence electrons as their nearest noble gas. 7 CHAPTER

Compounds, Ions, and Molecules A chemical bond (a force that holds atoms together to form compounds) can involve electron transfer or electron sharing. Ionic bonds involve a transfer of electrons between atoms. Ionic bonding forms ionic compounds. Covalent bonds involve a sharing of electrons between atoms. Covalent bonds form molecular compounds. Rules for writing chemical formulas and for naming ionic compounds are based on ion charge balances. Example: The chemical formula for sodium oxide is Na 2 O. 7 CHAPTER

Compounds, Ions, and Molecules Rules for writing chemical formulas and for naming molecular compounds are based on a prefix system. Ionic bonds involve a transfer of electrons between atoms. Ionic bonding forms ionic compounds. Molecular compounds result when atoms of non-metals bond by sharing electrons. 7 CHAPTER

Compounds, Ions, and Molecules Activity In chapter 6, we looked at chemical families (the columns) in the Periodic Table. In pairs, examine columns 1, 2, 16, and 17. Determine how many electrons each element would lose or gain to have the same number of electrons as its nearest noble gas. Do you notice a pattern within the chemical families? What generalizations can you make about the families and the ions they may form? Can you predict the ions group 13 elements will form? Confirm your predictions using the textbook (pages 172–173). 7 CHAPTER

Compounds, Ions, and Molecules 7 Key Ideas Compounds result when elements bond together in fixed proportions. Bohr diagrams can illustrate how ions form. Bonding can involve electron transfer (ionic) or electron sharing (covalent). Rules for writing chemical formulas and for naming ionic compounds are based on ion charge balances. Rules for writing chemical formulas and for naming molecular compounds are based on a prefix system. CHAPTER