Warm Up 9/21/17 In your folder, on paper, draw the Lewis Dot structures for the following elements: Potassium Silicon Fluorine Boron Chlorine Argon Phosphorus

Forces

What holds our world together? FORCES What is a chemical bond? The force that holds two atoms together

Review Why do atoms form chemical bonds? How? What does it mean when an atom is chemically unstable? What does the octet rule state? What subatomic particle is involved in forming chemical bonds? What is a molecule? How can the periodic table be used to determine the # of valence electrons? How can the periodic table be used to determine the # of energy levels? Most matter is electrically neutral, why? To become more stable by losing, gaining, or sharing electrons It does not have a full octet of electrons The outermost energy level has 8 valence electrons (full shell) Valence electrons Two or more elements chemically combined together Look at the group number Look at the period number The # of protons cancels out the # of electrons

[METALS ]+ [NON-METALS ]- IONic bonding Always formed between metals and non-metals [METALS ]+ [NON-METALS ]- Lost e- Gained e-

Formation of an Ionic Bond Ionic Bond (strongest) – b/w a metal and nonmetal that involves a gain or loss of electrons When an atom loses a valence electron to another atom, it becomes a (+) ion – CATION When an atom accepts a valence electron from another atom, it becomes a (-) ion – ANION

Na Cl EXAMPLE Metal Non-metal 1 valence e- 7 valence e- Cation – Na +1 Anion – Cl -1

They are now attracted to one another because one is positive and The other negative (opposite charges attract). A bond forms.

Na Cl EXAMPLE Metal Non-metal 1 valence e- 7 valence e- Cation – Na +1 Sodium chloride Na Cl 1 valence e- 7 valence e- Cation – Na +1 Anion – Cl -1

Na Cl EXAMPLE Metal Non-metal 1 valence e- 7 valence e- Cation – Li +1 Anion – F -1

Potassium Bromide Magnesium chloride

EXAMPLE Metal Non-metal Na Cl Calcium chloride

Lewis Dot Structure 2+ 1- DROP AND SWITCH THE CHARGES Shows the # of valence elecrons the atom has 2+ 1- What is the charge on Ca? What is the charge on F? How many atoms of Ca and F are needed? DROP AND SWITCH THE CHARGES

Drop and Switch Ca 2+ F- Drop Ca2 F1 Switch CaF2

Naming Ionic Bonds-Nomenclature *Cation is always written first, as it appears on the period table Then write the Anion changing the suffix (ending) of the anion to -ide

Properties of Ionic Compounds SALTS Crystals hard solid @ 22oC high melting point temperatures nonconductors of electricity in solid phase good conductors in liquid phase or dissolved in water (aq) Break apart/dissolve easily in water

Metallic Bonds Valence e- are mobile (move freely among all metal atoms) Metal to metal bonding

9/26/17 Notes- Covalent Bonds

2 Types of Forces Intramolecular Force (stronger)bonds between atoms holds elements together to make compounds, ex.)Ionic and Covalent Intermolecular Force (weaker) holds molecules together to form solids, liquids, and gases, ex.)Hydrogen bond.

COVALENT BOND bond formed by the sharing of electrons between nonmetals.

Properties of Molecular Substances Covalent bonding Low m.p. temp and b.p. temps relatively soft solids as compared to ionic compounds nonconductors of electricity in any phase

2 Types of Covalent Bonds Polar Covalent Bond – electrons are unevenly shared Nonpolar Covalent Bond – electrons are evenly shared (diatomics)

Non PolarCovalent Bonds Equal Sharing of electrons H-H

Non Polar Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

O O N N DOUBLE bond TRIPLE bond atoms that share two e- pairs (4 e-) atoms that share three e- pairs (6 e-) N N

when electrons are shared but shared unequally POLAR COVALENT BONDS when electrons are shared but shared unequally H2O

Oxygen has the ve- more of the time so it is slightly – Hydrogen has the ve- less often and is slightly + - water is a polar molecule because electrons are pulled closer to oxygen.

Water is a bent molecule H H

Intermolecular Forces:holds molecules together, weaker force EX.)Hydrogen Bond – when H bonds to N, O, or F Important in DNA (genetic material), proteins, and water molecules

Hydrogen “Bonding” Strong polar attraction Like magnets Occurs ONLY between H of one molecule and N, O, F of another H “bond”

Intermolecular Force – between different molecules Example: an interstate highway runs between different states

Intramolecular Force Intermolecular Force very weak Hydrogen bond Very strong Covalent bond Intermolecular Force very weak Hydrogen bond

Water Intramolecular force Intermolecular force

Nomenclature-naming covalent Compounds