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2.6 and 2.7 – Molecular and Ionic Compounds. Molecules and Chemical Formulas. Atoms bind to other atoms to form molecules Ionic Bonding : Giving and taking electrons (Metal-nonmetal bond) Covalent Bonding : Sharing electrons (nonmetal-nonmetal bond)
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Molecules and Chemical Formulas • Atoms bind to other atoms to form molecules • Ionic Bonding: Giving and taking electrons (Metal-nonmetal bond) • Covalent Bonding: Sharing electrons (nonmetal-nonmetal bond) • There are gasses that are bound to themselves as elements: Hydrogen = H2 Nitrogen = N2 Oxygen = O2 Fluorine = F2 Chlorine = Cl2 Bromine = Br2 Iodine = I2 You need to memorize these!
Formulas • We can represent molecules with molecular and empiricalformulas. • Molecular Formula = shows actual number of atoms in a molecule. • Empirical Formula = shows ratio of atoms in a molecule.
Class example Determine the empirical formula for the following compounds: 1. C6H12O6 2. N2O
Try it out! • Determine the empirical formula of the following compound: B2H6 • Is this a molecular or empirical formula: N4O6?
Ions and Ionic Compounds • Recall, an ion forms when an atom gains or loses electrons • Elements/compounds will gain or lose electrons in order to achieve a full outer valence shell. • Cation – A positively charged ion that forms when electrons are lost • Anion – A negatively charged ion that forms when electrons are gained. Cl Cl- Gains 1 electron, so it ends with a negative 1 charge Na Na+
Ionic attraction • Just like opposite poles of a magnet attract, oppositely charged ions attract. • Here, our positively charged Sodium Ion and negatively charged Chlorine Ion are attracted. • They remain ions, but stick together in a lattice (3D grid pattern) as other ions join them. Cl- Na+ Cl- Na+ Na+ Cl- Na+ Cl-
Determining Ionic Formulas • To determine the ionic formula that forms between two ions you need to do a few steps before beginning: • Make sure you have both a metal and non-metal. This indicates that an ionic bond will form • If a polyatomic ion is present, then make sure to put parentheses around it before beginning
2- + Na O Na2O
- 2+ K NO3 K(NO3)2
Class example Determine the formula when the following join in an ionic bond: 1. Sodium and oxygen 2. Potassium and phosphate
Try it out! • Lithium and fluorine • Ammonium and sulfate