SPARKS CH301 ELECTRONS and COMPOUNDS UNIT 2 Day 7 What are we - - PowerPoint PPT Presentation

SPARKS CH301 ELECTRONS and COMPOUNDS UNIT 2 Day 7

What are we going to learn today? Electron Configuration and Bonding

• Master using Lewis structures to predict

bonding in compounds

INDIVIDUAL QUIZ: CLICKER QUESTION

Referring to the position of Sr and P on the periodic table, would you predict these elements would come together to: A) Form a metallic compound B) Form a covalent compound C) Form an ionic compound

Relate electron configuration to periodic table

IONIC BONDING: SUMMARY

Electrons transferred from one element to another Forms lattice of anions (negative ions) and cations (positive ions) held together by a (strong) electrostatic attraction

Consider bonding of identical non-metal atoms: H2

• No incentive for either to gain or lose electrons

COVALENT bonding

Atoms share valence electrons with other atoms to try to attain noble gas configurations.

• The two nuclei REPEL
• The electrons REPEL
• BUT...the electrons are ATTRACTED to both

nuclei!

Covalent Compounds

Characterize the bond…. Bond Length Bond Strength Electron Pair Shared Equally? YES – PURE COVALENT NO – POLAR COVALENT

Electronegativity: electron pulling power of an atom when it is part of a molecule

• When one atom is more electronegative than

another in a bond, a polar covalent bond is formed.

• Degree of polarity is dependent on difference in

electronegativities.

Ionic vs Covalent Bonds

All bonds can be viewed as hybrids between purely ionic and purely covalent

(a) X and Y have identical ENs.

(b) X and Y have dissimilar ENs. (c) X and Y have very different ENs.

Continuum of bonding types

*For your reading later*

• All bonds can be viewed as hybrids between purely ionic and

purely covalent

• When two identical atoms are bound, it is purely covalent.
• When two different atoms are bound, one may have a greater

attraction for electrons, and have a partial negative charge.

• Polar covalent bond – degree is measured as dipole moment
• When one atom has a much stronger attraction to the

electrons than the other, an electron may be donated yielding an ionic bond.

Which of the following bonds would you expect to be classified as polar covalent? KF CO O2

• A. KF, with the F end having a partial negative charge.
• B. KF, with the K end having a partial negative charge.
• C. CO, with the O end having a partial negative charge.
• D. CO, with the C end having a partial negative charge.
• E. O2, with neither end having a partial negative charge.

POLLING QUESTION

Covalent Compounds - Naming

Covalent Compounds What is attached to what?

Valence electrons – Lewis symbols – Lewis Structure – Satisfy the Octet

H2 CH4

Determine total number of valence electrons Predict total number of Bonds : S = N – A rule Draw Skeletal Structure Place nonbonding electrons Fix the number of bonds

LEWIS STRUCTURE RULES

Demonstrate using the rules to show how to put together Lewis structures.

C2H6

CH4

Examples from Activity

C2H2 C2H4

Take a little moment….

Bond Strength Bond Length

Single Double Triple

Examples 4, 5 and 6 from Activity

CH3OCH3 C2H5OH C2H6O

Hints for Lewis Dot structures

1. C almost always has 4 bonds and NO lone pairs

• 2. H always forms ____ bond
• 3. Halogens tend to form ____ bond.
• 4. How many bonds do you think C, N, and O
• ften have?

What have we learned?

ATOMS BEHAVE IN CERTAIN PREDICTABLE WAYS WHICH CAN BE CORRELATED TO THE ELECTRON CONFIGURATIONS SATISFYING THE OCTET RULE IS A SOLID PREDICTOR OF BONDING IN IONIC AND COVALENT COMPOUNDS

Learning Outcomes

Draw the Lewis structures for molecular compounds and ions. Use Lewis structures to predict and explain the relative bond Strength and lengths in compounds. Recognize and apply exceptions to the octet rules.

Important Information

HW due Monday. Want more help? Non-graded LM: Laude LM Lecture 8