Unit1%Test - kippchemhart.weebly.com€¦ · b) C and H ! !d) F and C! Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference

Unit 1 Test

•  Class average: 76% •  Class goal: 80% •  SHOUT OUTS!

– Nelson – Elvin – Sapphire – Noel – Daouda

(Period 3)

Welcome to Chemistry Regents Prep… SILENTLY… 1.  Complete the Do Now (ON YOUR SHEET) 2. Write down tonight’s homework:

•  HW 2.3

IMPORTANT DATES: Bonding test on FRIDAY Sept 19

AIMs: How do non-‐metals distribute shared electrons among non-‐metals?

AGENDA: •  Do now [8] •  Quiz [8] •  Notes – ElectronegaCvity and Polarity [10] •  Regents QuesCon Think Aloud [10] •  Homework [25]

•  ElectronegaSvity: The tendency of an atom to aVract electrons toward itself.

ElectronegaSvity •  Across a period: ElectronegaSvity Increases

– As the number of protons increases, electrons are more strongly aVracted and hence…

– They will have more pull on other atoms electrons

Objective: SWBAT explain trends in electronegativity

ElectronegaSvity Down a group: ElectronegaSvity Decreases

– There are more energy levels. – ProspecSve electrons from other atoms will be shielded from the aVracSon forces of the addiSonal protons by other energy levels of electrons


Down a Period

3 P+ 11 P+

Li Na


Tug of War

vs.

Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference of the atoms, identify a molecule as polar or nonpolar based on it’s bond polarity and symmetry

Electron Tug of War

Diagram 1 Diagram 2

H H H F


Polarity**: property of molecules with poles (or uneven charges)

Electronegativity Difference �

EN Difference � Bond Character �

> 2.0!

1.0-2.0!

0.4-1.0!

0-0.4!Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference of the atoms, identify a molecule as polar or nonpolar based on it’s bond polarity and symmetry

IONIC BONDS (difference in EN >2.0 = METAL and

NONMETAL) ex. NaCl

Electrons fully transferred (caCon and anion formed)


Nonpolar Covalent (difference in EN = 0-‐0.4)

ex. N2 or O2

Electrons shared equally (li`le or no charge difference between atoms)


Polar Covalent (difference in EN >0.4, < 2 )

ex. NO, HO, HF

Electron shared unequally (charge difference between atoms)


In an ionic bond, what happens to the valence electrons?

In a covalent bond, what happens to the valence electrons?


In a nonpolar covalent bond, what happens to the valence electrons?

In a polar covalent bond, what happens to the valence electrons?


Polar Bonds �

Which atom aVracts electrons more? How do you know?

Is HCl polar or non-‐polar? Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference of the atoms, identify a molecule as polar or nonpolar based on it’s bond polarity and symmetry

The electrons in a bond between two iodine atoms (I2) are shared….

equally, and the resulSng bond is ….

non-‐polar covalent


The electrons in a bond between hydrogen and oxygen atoms are shared….

unequally, and the resulSng bond is ….

very polar covalent

EN difference = Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference of the atoms, identify a molecule as polar or nonpolar based on it’s bond polarity and symmetry

Practice �•  Which elements will form a bond with

the most ionic character?!a)  H and F ! !c) C and O!b)  C and H ! !d) F and C!


•  Nonpolar Covalent –  Electrons are shared equally – Ex: bond between 2 idenScal nonmetals

•  Polar Covalent –  Electrons are not shared equally –  One atom is more electronegaCve

•  Ionic –  Electrons are transferred –  One atom is much more electronegaCve


PracSce Polar Bonds

•  a) Draw the Lewis dot structure, b) Label each bond as polar (P) or non-‐polar (NP) c) For polar covalent bonds, draw a δ-‐ or δ+ on the atom for each bond. d) Label the shape that the molecule will have (use your notes from 5.10).


Polarity of Bonds vs. Molecules �

• Molecules can be non-polar even if bonds are polar!– Molecules need to be symmetrical for

this to occur!• Ex: CCl4!


Symmetrical Compounds Chlorine is more electronegative

Pulling evenly in all four directions!!


Non-‐Symmetrical Compounds

Pulls electrons away from the hydrogen and carbon

Chlorine is more electronegative than Carbon

Carbon is more electronegative than Hydrogen

δ+ δ-


Dipole** is a molecule with two poles.

δ+ δ- Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference of the atoms, identify a molecule as polar or nonpolar based on it’s bond polarity and symmetry


Which is more electronegative Cl or F?

δ- δ+


•  What geometry did CO2 and H2O have?

C O O


Water vs. Carbon Dioxide •  Linear molecules can be symmetrical if they have the same atom on either side

•  Bent molecules are never symmetrical! – More NegaSve Near Oxygen

C O O

δ-

δ+


Which can be symmetrical? •  Linear

– SomeCmes •  Bent

– Never •  Trigonal Planar

– SomeCmes •  Tetrahedral

– SomeCmes •  Trigonal Pyramidal

– Never


Trigonal Pyramidal Shape

NH3


AddiSonal QuesSons?

Unit1%Test - kippchemhart.weebly.com€¦ · b) C and H ! !d) F and C! Objective: SWBAT determine whether a bond is polar, nonpolar or ionic based on the electronegativity difference

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