Day 1 Quiz Today ! Pick up papers on the lab table. Put all your books and papers under your desk. Take out a pen/pencil & vocabulary cards! Be in your seat when the bell rings. The quiz will start right away! Day 1

Reading Quiz 8-2 1. When atoms in a molecule equally share electrons, the bond formed is ____________. 2. Unequally shared electrons are found in __________ bonds. 3. The bond type can be found by subtracting the two atom’s _____________ numbers. 4. In a polar molecule, one end of the molecule is slightly __________ and the other end is slightly __________. 5. A molecule that has two poles is called a _____.

Warm-ups 1-3 Warm-up 1-3 Draw the structural formulas for: 1 - CH2Br2 2 - H2O2 - Watch out: there are 2 central atoms! 3 - CH3NH2 - Watch out: there are 2 central atoms! Warm-up 1-3

N S O H H H Warm-up 4 Warm-up 4 (A) (B) 1 - What is the molecular shape of each molecule? 2 - What is the bond angle of each? 3 - Why are the bond angles different? Warm-up 4

Molecular bond-shape around the carbon central atom is tetrahedral. Warm-up 1 Br Molecular bond-shape around the carbon central atom is tetrahedral. 109.5o C H H Br Draw the structural formula for CH2Br2. Warm-up 1

H O O H Warm-up 2 Warm-up 2 Draw the structural formula for H2O2. Molecular bond-shape around the oxygen central atom is bent. H 105o O O 105o H Draw the structural formula for H2O2. 180o Warm-up 2

Molecular bond-shape around carbon central atom is tetrahedral. Warm-up 3 H Molecular bond-shape around carbon central atom is tetrahedral. 109.5o C N H Molecular bond-shape around the nitrogen central atom is trigonal pyramidal. 107o H H H Draw the structural formula for CH3NH2. 180o Warm-up 3

N S O H H H Warm-up 4 Warm-up 4 (A) (B) 1 - What is the molecular bond-shape of each molecule? 2 - What is the bond angle of each? 3 - Why are the bond angles different? Warm-up 4

Lecture 8C – Bond Polarity

There are 3 types of bonds. Bond Polarity Bonding pairs of electrons may or may not be shared equally in a molecule. 1 - The greater the electronegativity value, the greater the ability for an atom to attract the bonding e- to itself. 2 – Bond type is found by subtracting two bonded atoms’ electronegativity values. Electronegativities is based on a unitless scale from 0-4 There are 3 types of bonds. Bond Polarity

Electronegativity Difference Bond Types Electronegativity Difference Electron Sharing Covalent Nonpolar Covalent Polar Ionic 0.00 0.01 – 1.9 2.0+ Electronegativities is based on a unitless scale from 0-4 shared equally shared unequally not shared at all!

What does “unequal sharing” look like? The bonding electrons are displaced more towards the atom with the greater electronegativity, leaving partial charges on the molecule.

Na+ Cl- = NaCl = K2O K+ O2- Transferred Example – Ionic Bonding 0.9 3.0 = 2.1 The electrons are not shared between the two atoms but they are: Transferred Therefore: partial charges are not drawn because the e- are NOT shared. = K2O K+ O2- 0.8 3.5 = 2.7

C H C F Example – Covalent Polar Bonding 2.5 2.1 = 0.4 4.0 = 1.5 2.5 The atom that is more electronegative (stronger attraction of e-) acquires a partially-negative charge & the less electronegative acquires a partially-positive charge. A delta symbol is used to show the attraction. The more electronegative atom will have the stronger electron attraction & acquire a slightly negative charge. A small partial positive charge on hydrogen & a small positive charge on carbon. C F 4.0 = 1.5 2.5

H H C C Example – Covalent Non-Polar Bonding 2.1 2.1 = 0.0 2.5 = 0.0 The electrons in the covalent bond are equally shared. There are no partial charges. The more electronegative atom will have the stronger electron attraction & acquire a slightly negative charge. A small partial positive charge on hydrogen & a small positive charge on carbon. C C 2.5 = 0.0 2.5

Molecular Polarity Molecular Polarity Definition: Dipole - A molecule that has two poles, one end is partially (+) and the other end is partially (-). Must know: 1 - bond polarity & 2 - molecular shape (VSEPR) to predict molecule polarity! Molecular Polarity

Molecular Polarity ex: CH3Cl ex: bent & t-pyramidal Definition - Polar Molecule 1. Must have at least 1 polar bond. This is required! 2. Most molecules with lone pairs on the central atom are polar! ex: bent & t-pyramidal 3. Tetrahedral shape must be unsymmetrical 105o ex: CH3Cl Different atoms bonded to the central atom.

Molecular Polarity Definition - Nonpolar Molecule 1. Might have polar bonds. 2. Molecules with no lone pairs on the central atom are often nonpolar. ex: trigonal planar & linear 3. Tetrahedral shape must be symmetrical! ex: CH4, CF4 (all atoms bonded to the central atom are the same)

Polar or Nonpolar Molecule Example 1 Electronegativity difference O-H: 3.5 - 2.1 = 1.4 Bond very polar or nonpolar? O 3.5 H H 2.1 2.1 Draw the structural formula for H2O Polar or Nonpolar Molecule Why??

Draw the structural formula for CO2 Example 2 2.5 3.5 3.5 C O O Electronegativity difference O-C: 3.5-2.5 = 1.0 Bond very polar or nonpolar? Draw the structural formula for CO2 Polar or Nonpolar Molecule Why??

Draw the structural formula for CH3Cl Polar or Nonpolar Molecule Example 3 Electronegativity difference Cl-C: 3.0-2.5 = 0.5 3.0 Cl Bond polar or nonpolar? 2.5 Bond polar or nonpolar? C H H 2.1 2.1 H Electronegativity difference C-H: 2.5-2.1 = 0.4 2.1 Draw the structural formula for CH3Cl Polar or Nonpolar Molecule Why??

Polar or Nonpolar Molecule Example 4 2.1 H Electronegativity difference C-H: 2.5 - 2.1 = 0.4 2.5 C Bond polar or nonpolar? H H H Why?? Draw the structural formula for CH4 Polar or Nonpolar Molecule

Draw the structural formula for PH3 Example 5 Electronegativity difference P-H: 2.1-2.1 = 0 2.1 Bond polar or nonpolar? P H H H 2.1 Draw the structural formula for PH3 Polar or Nonpolar Molecule Why??

Polar or Nonpolar Molecule Worksheet C Molecular bond-shape around the oxygen central atom is bent. 105o H 3.5 O O H Why? 2.1 Show the electronegativity values & bond polarity for H2O2. Polar or Nonpolar Molecule Worksheet C

Polar or Nonpolar Molecule Worksheet C 3.5 O Bond is very polar C Bond is slightly polar 2.5 H H 2.1 2.1 Show the electronegativity values & bond polarity for CH2O. Polar or Nonpolar Molecule Why?? Worksheet C