qotd How many valence electrons do Cl, and Na have? How is an ion made? What do you think of when you think of the word “bond”?

Chemical Bond

attraction of nuclei for electrons Chemical Bond attraction of nuclei for electrons All atoms try to get a stable octet p+ in one nucleus are attracted to e- of another atom

What did the atom of chlorine say to the atom of sodium? You complete me.

Two Major Types of Bonding Covalent Bonding forms molecules sharing e- forms ionic compounds transfer of e- Ionic Bonding Two Major Types of Bonding

One minor type of bonding Metallic bonding like atoms of a metal in the free state Valence e- are mobile Positive ions in a sea of electrons

It’s the mobile electrons that enable me-tals to conduct electricity!!!!!!

electrons are transferred between valence shells of atoms IONic Bonding NOT MOLECULES electrons are transferred between valence shells of atoms ionic compounds are made of ions ionic compounds are called Salts or Crystals

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

NaCl CaCl2 IONic Bonding Electronegativity difference > 2.0 Look up e-neg of the atoms in the bond and subtract NaCl CaCl2 Compounds with polyatomic ions NaNO3

qotd What kind of elements make ionic bonds? What kind of elements make covalent bonds? How do you make an ion with a +2 charge? What kind of bonds make up you? Why

Properties of Ionic Compounds hard solid @ 22oC high mp temperatures nonconductors of electricity in solid phase good conductors in liquid phase or dissolved in water SALTS Crystals

Pairs of e- are shared between non-metal atoms Covalent Bonding molecules Pairs of e- are shared between non-metal atoms electronegativity difference forms polyatomic ions

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

Chemical Bond

Covalent, Ionic, metallic bonding? NH4+ Aluminum phosphate KH KCl HF CO Co NO2 sodium hydride Hg H2S sulfate Also study your characteristics!

Drawing ionic compounds using Lewis Dot Structures Symbol represents the KERNEL of the atom (nucleus and inner e-) dots represent valence e-

[Na]+ [ Cl ]- NaCl How did we get here? This is the finished Lewis Dot Structure [Na]+ [ Cl ]- How did we get here?

Step 1 after checking that it is IONIC Determine which atom will be the +ion Determine which atom will be the - ion Step 1 after checking that it is IONIC Write the symbol for the + ion first. NO DOTS Draw the e- dot diagram for the – ion COMPLETE outer shell Step 2 Enclose both in brackets and show each charge Step 3

Draw the Lewis Diagrams LiF MgO CaCl2 K2S

Drawing molecules using Lewis Dot Structures Symbol represents the KERNEL of the atom (nucleus and inner e-) dots represent valence e-

Always remember atoms are trying to complete their outer shell! The number of electrons the atoms needs is the total number of bonds they can make. Ex. … H? O? F? N? Cl? C? one two one three one four

Methane CH4 How did we get here? This is the finished Lewis dot structure How did we get here?

IF the central atom has 8 valence e- surrounding it . . YOU’RE DONE! count total valence e- involved Step 1 connect the central atom (usually the first in the formula) to the others with single bonds Step 2 complete valence shells of outer atoms Step 3 add any extra e- to central atom Step 4 IF the central atom has 8 valence e- surrounding it . . YOU’RE DONE!

Sometimes . . . You only have two atoms, so there is no central atom, but follow the same rules. Check & Share to make sure all the atoms are “happy”. Cl2 Br2 H2 O2 N2 HCl

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

Draw Lewis Dot Structures You may represent valence electrons from different atoms with the following symbols x, , CO2 NH3

Draw the Lewis Dot Diagram for polyatomic ions Count all valence e- needed for covalent bonding Add or subtract other electrons based on the charge REMEMBER! A positive charge means it LOST electrons!!!!!

Draw Polyatomics Ammonium Sulfate

Types of Covalent Bonds NON-Polar bonds Electrons shared evenly in the bond E-neg difference is zero Between identical atoms Diatomic molecules

Types of Covalent Bonds Polar bond Electrons unevenly shared E-neg difference greater than zero but less than 2.0 closer to 2.0 more polar more “ionic character”

non-polar MOLECULES Sometimes the bonds within a molecule are polar and yet the molecule is non-polar because its shape is symmetrical. H C Draw Lewis dot first and see if equal on all sides

Polar molecules (a.k.a. Dipoles) Not equal on all sides Polar bond between 2 atoms makes a polar molecule asymmetrical shape of molecule

H Cl + -

Water is asymmetrical + + H O -

Water is a bent molecule H H

Making sense of the polar non-polar thing BONDS Non-polar Polar Identical Different MOLECULES Non-polar Polar Symmetrical Asymmetrical

IONIC bonds …. Ionic bonds are so polar that the electrons are not shared but transferred between atoms forming ions!!!!!!

VSEPR Theory Valence Shell Electron Pair Repulsion Theory Electron pairs orient themselves in order to minimize repulsive forces. C. Johannesson

Lone pairs repel more strongly than bonding pairs!!! VSEPR Theory Types of e- Pairs Bonding pairs - form bonds Lone pairs - nonbonding e- Lone pairs repel more strongly than bonding pairs!!! C. Johannesson

4 Shapes of molecules

1. Linear (straight line) Ball and stick model Space filling model

2. Bent Ball and stick model Space filling model

3.Trigonal pyramid Ball and stick model Space filling model

4.Tetrahedral Ball and stick model Space filling model

Intermolecular attractions Attractions between molecules van der Waals forces Weak attractive forces between non-polar molecules Hydrogen “bonding” Strong attraction between special polar molecules

van der Waals Non-polar molecules can exist in liquid and solid phases because van der Waals forces keep the molecules attracted to each other Exist between CO2, CH4, CCl4, CF4, diatomics and monoatomics

van der Waals periodicity increase with molecular mass. increase with closer distance between molecules Decreases when particles are farther away

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

H is shared between 2 atoms of OXYGEN or 2 atoms of NITROGEN or 2 atoms of FLUORINE Of 2 different molecules

Why does H “bonding” occur? Nitrogen, Oxygen and Fluorine small atoms with strong nuclear charges powerful atoms very high electronegativities

Intermolecular forces dictate chemical properties Strong intermolecular forces cause high b.p., m.p. and slow evaporation (low vapor pressure) of a substance.

Which substance has the highest boiling point? HF NH3 H2O WHY? Fluorine has the highest e-neg, SO HF will experience the strongest H bonding and  needs the most energy to weaken the i.m.f. and boil