chapter 3

compound

a substance made from two or more different types of elements that are chemically joined in a fixed ratio

ionic compounds (form between, structure, electron movement)

• result from bonds forming between positive metal ions and negative non metal ions

• these compounds form a lattice structure

• ionic compounds are often called salts. they swap or exchange electrons

• example: NaCl (sodium chloride)

covalent compound (form between, structure, electron movement)

• result from bonds forming between non-metal atoms

• forms discrete molecules

• form molecules by sharing electrons

• e.g. H²O

types of compounds

• ionic compounds, which result from bonds forming between metals and non-metal or positive ions and negative ions. Ionic compounds form salts and crystalline lattices.

• covalent compounds, which result from bonds forming between non-metal atoms. Covalent compounds form molecules.

• metallic compounds, which result from bonds forming between metal atoms. Metallic compounds form metals or alloys.

naming ionic compounds

• ionic compounds are named with the metal first (or cation for NH +/4) followed by the correctly named non metal ion

• e.g. Na^2O -> sodium (name of metal) oxide (name of metal ion)

ionic bond (def)

a type of chemical bond that occurs between oppositely-charged ions

writing formula of ionic compounds steps

1. find the formula (symbol and charge) for each ion)

   • Na^+ S²-

2. balance the charges to add up to 0 (diagram)

   • Na^+ \\

S²-

Na^+ //

2. balance the charges to add up to 0 (check)

   • + 2 - 2 + 0

3. write the formula and name

   • Na²S SODIUM SULFIDE

   • subscript shows there are two Na^+ ions bonded to one S²- ion

   • do not write charges

covalent bond

• a type of chemical bond that occurs between non-metal atoms

• electrons are shared to achieve full valence shells and molecules are formed

naming rules for covalent compounds

1. write the name of the first element in the formula - usually the furthest to the left on the periodic table

2. write the name of the second element and replace its ending with ‘ide’

3. the number of atoms of each element present in the molecule is indicated by a prefix

   • exception - mono is not used for the first element

   • mono - 1, di - 2, tri - 3, tetra - 4, penta - 5, hexa - 6, hepta - 7, octo - 8, nona - 9, deca - 10

diatomic elements

• elements that form molecules with themselves

• composed of two atoms of the same element

• there are 7 and they make a 7 shape on the periodic table

• Have No Fear Of Ice Cold Beer

• All end in ‘gen’ or ‘ine’ - genuine

• in covalently bonded molecules atoms forms bonds by sharing electrons to achieve full valence shells

• H, N, O, and the Group 17 elements form diatomic elemental gases.

properties of ionic compounds, covalent compounds, metallic compounds

1. Ionic Properties

• Forms a salt

• Forms a crystalline lattice

• Electrons are exchanged

• Occurs between positive and negative ions

• Occurs between metals and non-metals

2. Covalent Properties

• Forms a molecule

• Electrons are shared

• Occurs between non-metal elements

3. Metallic Properties

• Forms a crystalline lattice

• Forms a metal or alloy

• Electrons are shared

• Occurs between metal elements