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UCR / Chemistry / CHEM 001A / What are tetrahedral sigma bonds?

What are tetrahedral sigma bonds?

What are tetrahedral sigma bonds?

Description

School: University of California Riverside
Department: Chemistry
Course: General Chemistry
Professor: Hill harman
Term: Fall 2018
Tags: General Chemistry
Cost: 25
Name: Chem001A wk.6 notes
Description: Chem001A in-class notes for week 6 covering chapter 5.
Uploaded: 11/12/2018
3 Pages 34 Views 1 Unlocks
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monday november 5, 2018 MOLECULAR SHAPE i chemical L.physical properties related to molecular shape


What is tetrahedral sigma bonds?



- lewis structures

show atoms and bonds, but not spatial Orientations (3-D)

molecular models

Show Orientation and bond angles, helps us understand physical and chemical properties Don't forget about the age old question of What is the real exchange rate?

Com O=C=0

CHy Hot Dc

# H

Н VALENCE SHELL ELECTRON PAIR REPULSION (VSEPR) INSEPR theory


What are the requirements for polar molecules?



- model predicting that the arrangement of valence electrons pairs around a central atom

minimizes repulsion to produce the lowest energy onentation

electron pair geometry VSEPR : ELECTRON PAIR GEOMETRY 1. to determine electron Inc. draw lewis structure

from lewis structure, determine steric number (SN) SN= # of atoms bonded & # of lone pairs bonded


What is the most common sn?



We also discuss several other topics like What is pseudoparticipation?

T to central atom If you want to learn more check out What are the two types of shorelines?

to central atom I determine optimal spatial arrangement of electron pairs (bonding t nonbonding) to minimize repulsion We also discuss several other topics like What is the difference between interference and diffraction?

COLE

M

C

up

IL

F

-do not use on

utrol Ibonds

t

-c

-

H

tetrahedral

de

A going in going out

SN = 4

t

o

atoms bonded

= 42.

lone pairs Don't forget about the age old question of Does neuroscience really bear on the truth of theories of moral motivation?

Clip)

NH3

molecular geometry. trigonal pyramice

(blc one is lone pair)

H HH I SN= 3 bonded t

- atoms

I L.P. = 4

electron

tetrahedral

geometry

- molecular geometry = electron pair

determine steric number (SN):

SN-2

geometry = linear SN=3

geometry = trigonal planar SN=4 o tetrahedral SN = 5 trigonar bipyramidal We also discuss several other topics like Define personality disorders.

SN=6 octahedral Central atom with no lone pairs

1

steric number = electron pair

geometry

осно".

WE

ELL

SN

SN=3

109,50

109,5°

SIN=4

SN=4

Ą SN=2 120d SN=8 90 47 120

GEOMETRIC FORMS

BE

B

-

F

24 VE

no multiple bonds to halogens

PRACTICE : MOLECULAR

GEOMETRY (NO CONE PAIRLS).

- SN=3

trigonal planar

O SN electron pair

geometry * if no lone pairs

electron geometry pair = molecular geometry

-

SN=4

tetrahedral

formula

lewis structure

p steric number

I bonded atoms t lone pairs )

&

no lone pair EPG = molecular

electron pair

geometry

geo.

CENTRAL ATOMS WL LONE PAIRS

molecular geometry 7 electron pair geometry

replace bonding pair (s) with lone pairls) 502 8 VE.

EPG is trigonal planar 30 - Ś - Ö:

on M6 = bent 0 - s = 8 SN=3 #2 atoms & not linear = bent

1 - 0 -+

SN=4

a

osiyor

tetrahedral

M207

I IMOD

.

::07:03

H

I H 109.5°

~12.0°

• bond angles less than predicted - electron pair repulsion

lone pair - lone pair = greatest repulsion lone pair - bunding pair - bonding pair - bonding pair = least repulsion

multiple bonds single bond

(1 big pushing 1095 0 0

Nu down to 120° 2

- 5 * Note: hond angles decrease as # of lone pairs increases

-

H

H

I

i

s.

→ S.N.

-

-> E.P.6.

angles

M.G. lignore l.p.)

H

109.5°

104.50

two lone pairs =

greater repulsion, decreased bond

angle

NUN

november 7, 2018

LE

Wednesday

VESPER

based on ( SN =

steric number (SN) #bonded atoms &

L.P.

H-6-H

н Nitz

н

-

city

SN=4 tetrahedral

SN=u EPG = tetrahedral molecular geometry (MG) = frigonal

pyramidal EPG: (linear), 3 (trigonal planar),

Lo steric number -

- lowest SN is 2

y (tetrahedral ), 5 l trigor ad bipyramidal)

79 109.50

ce coctahedral) - most common SN are 2 -4 - when SN > 4 then it violates octet - SV 2 to SN y have 7 bond angles

SN 5 and SN ce have a bond angles LEPO includes lone pairs but no is just l. if no lore pairs EPG = MG (ex.cty )

atoms

SŅUp

2

0

ili

linear ?cus H CENi only

I atom

bound

SN

trigonal planar bent la 120°

from

cus bent derived trig: planar )

SN

СР

Tetrahedral trigonal planar bent ( 109.50 derired from

tetrahedral)

xty

1

***

VA

!

trigonal pipyramidal

seesan

xt t-shape

linear I SN=5

- p can be in axial or [ 120° equatorial site, preference for

e E since 1200 > 90° Iguels & room) 4

Isimple atoms E, complex can use AS & Note: Lone pairs occupy squatorial positions I SN

octahedral square pyramidal &

square planar Isn=6

Note: - bond angles = 90°

geometries w/ more than)

12 lone pairs possible * doesn't predict transition metals * generally don't talk about SN:7 because [rare and VESPER does not apply

LP

of

the long

PRACTICE : MOLECULAR GEOMETRY

What are the molecular geometries

SCN- and NO2 - ? [Son] -

Cu B

gre SECOND

16V.E. [NO] -a

5 6 18 vie.

:0 = Ñ - ö: 0

A

nonpolar

geometric classes defined by valence electrons * H - H nonpolar H-F polar ------

more EN

t dipole in bond loro polaro = c = 0

tt. blc cancel POLAR BONDS AND POLAR MOLECULES

requirements for Polar molecules: L 1. polar bonds li.e covalent bonds between atoms.

- with AEN) 2. nonuniform distribution of polar bonds

OYUN

sides cancel up & down reinforce

N

t

it

I MEASURING POLARITY

dipole moment (1) a quantitative expression of the polarity of a molecule,

Units a debyes (D)

0-2 between polar

x

in

general resonance will not some times wrong one's can molecular composition

affect polarity

affect

-

-

FRIDAY NOVEMBER 9 2018

CHAPTER OUTLINE molecular Shape valence - shell electron - pair repulsion

theory (VSE PR)

polar bonds and polar molecules valence bond theory and hybrid orbitals

molecules with multiple central atoms 1 chirality and molecular recognition

. molecular orbital theory atomic ORB ITALS_AND BONAS "valence bond theory (Linus pauling)

quantum mechanics-based model

covalent bond = overlap of orbitals

• Sigma (o) bond:

covalent bond having highest electron density between the two atoms

along the bond axis

All D *will look - overlap of 15 orbitals

like sphere

chy

tetrahedral

4 x IS (H)

25 (0) 3 x 2p (6)

A

AY

X

HYBRIDIZATION ; sp3 orbitals

• hybridization : mixing of atomic orbitals to

generate new sets of equivalent orbitals that form covalent bonds with other atoms

.

- 109.50

one to each other * key concept in valence bond theory TETRAHEDRAL SIGMA BONDS

tefraneelral orientation of sp3 hybridized orbitals = tetrahedral molecular geometry t overlap of is with sp3 orbitals

tetrahedral (SN 4) = sp2 o Sn=3 - trigonal planar

~ 1200 HCH

ott

a 3x sp2 o in bond CH 0 0

* -hare extra p orbitur COO---- - double bond

o + Honda Inocle * Orbitals cannot be created on

no nodes contain bond access destroyed sp? HYBRIDIZATION

• pi (IT) bond

electron density is concentrated above / below the bonding axis

& single bonde electron density is where it wants

to be so stronger

e low energy stronger 1200

SN Y

double bond = sp2 a I sp3 SP2 (p) sp (2xp)

2 tetrahedral trig planar linear

O + ∞ = 20

HOC E C -H

LINEAIR: sp

form

hYBRIDIZATION

triple wond Cone 0 and

T bonds)

two

100

-

wrong

& no quadruple bonds no allow more than in

lo and 2 π - deals with hybridization

- C (arguments about it unstable) X TRIGONAL BIPYRAMIDAL: Sp2d hyBRIDIZATION T

sp3 d -> SN5 - trig, bipyramidal - if sp2d2 - SNG octahedrali c transition

metals not

in expanded tuseful to know but wrong in context octet

Bt2 it

"!

trigonal planar a

- B - H

Isen] S=C=NO>;S-CIN:

sp2

sp

sp2 sp

sp

sp

1 OVA

TI

LLLLS

Practice Hybrid Orbitals [NO2] | What is the hybridization

of the centrul atom for the ions: SON- and NO2?

Opel

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