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UCR / Biochemistry / CHEM 001 / In chemistry, what defines a trigonal pyramidal?

In chemistry, what defines a trigonal pyramidal?

In chemistry, what defines a trigonal pyramidal?


School: University of California Riverside
Department: Biochemistry
Course: General Chemistry
Professor: David hill
Term: Fall 2018
Tags: Chem, Chemistry, General Chemistry, lewis dot, Lewis Structure, lewis model, covalent bonds, Covalent Bond, ionic bonds, Ionic Bond, octet rules, Octet Rule, octet, octetrule, octets, VSEPR, VSEPR shapes, VSEPR theory, VSEPR models, atom hybridization, hybridization, hybridizations, hybridizationstate, valence bond theory (hybridization, chirality, and Chiral
Cost: 50
Name: General Chemistry Midterm 2 Study Guide--Chapters 4-6
Description: A cumulative study guide based off of notes taken during lecture and discussion as well as with some help from the textbook. Touches on important key subjects that will most likely be on the midterm su
Uploaded: 11/22/2018
12 Pages 36 Views 3 Unlocks

Midterm Study Guide 

In chemistry, what define a trigonal pyramidal ?

• Chapter 4 

o Naming compounds & writing formulas 

▪ Become familiar with polyatomic ions 

o Lewis symbols 

▪ Diagrams that show bonding between atoms of a 

molecule and the lone pairs that may exist in the 


o Resonance—electron movement (generally from an  electronegative atom) 

▪ Way of describing delocalized e’s 

o Elecronegativity, unequal sharing and polar bonds 

▪ Ionic bonding 

What is the function of octet rule?

We also discuss several other topics like How long does it take to conduct down axons?

Usually one, two, or 3 e’s are transferred from one  atom to another

▪ Covalent bonding 

Sharing of electrons

Lewis dot structures diagrams that show, what?

Octet rule: Atoms lose, gain, or share electrons in order to have a  full valence shell of 8 e’s

Formal charge: A formal charge is a comparison of electrons owned by an  atom in a Lewis structure vs. The # of e’s possessed by the same atom in its  unbound, free atomic state.

Lewis dot structures: diagrams that show bonding between atoms of a  molecule and the lone pairs that may exist in the molecule. We also discuss several other topics like Which drugs are used for lethal injection?
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FC=(# of valence e’s)-(# of electrons in a lone pair)+(1/2 of shared e’s)

Formal Charge

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Complete the Lewis Dot Structure for HOCl 

HOCl>all formal charges are zero

NO3—Draw the Lewis Dot Structure 

o Determine v e’s in the molecule 

N 5

Ox(3) 18

V e’s 1 

24 e’s

o Draw skeleton using only single bonds 

18 left

o Start with electronegative atom first If you want to learn more check out Who organized the first convention on women's rights?

o Ask: Are all octets filled? 

If not, fill remaining octets by making multiple bonds. (lone pair  atom electroneg atom into bonding pair)

o Check formal charges 

FC equ: 6-1-6=-1


• Chapter 4 (cont.) 

o Lewis Dot Structures 

o Formal charge of an atom 

Specified FC equ=(# of valence e’s on atom)-(# of e’s in lone pairs[# of  non-bonded e’s])-1/2(# of e’s shared in bonds)

Expanded Octet: 

▪ In general, atoms in the fourth period and beyond, higher  d orbitals can be used to accommodate additional shared  e’s. 

▪ Main group elements that form more bonds than 

predicted by the octet rule are called hypervalent 

compounds, and have what is known as an ‘expanded 

octet,’ meaning????more than 8 e’s around on atom. 

Octet Rule: 

▪ Atoms bond in such a way that each atom acquires 8 e’s  in its outer shell. 

Lewis Dot: 

▪ Shows valence electrons indication the bonding between  atoms.

Draw the Lewis dot structure for the following compounds: BeF2 PBr5 BCl3 SI6 CCl4 BH2^- H2S

▪ Octet rule can be ‘expanded’ by some elements utilizing  the d-orbitals found in the third principal energy level and  beyond. Sulfur, phosphorous, silicon and chlorine are 

common examples of elements that form expanded 


FC—comparison of e’s and ‘owned’ by an atom in a Lewis structure vs. the  number of e’s possessed by the same atom in its unbound, free atomic  state

• Valence Shell electron pair repulsion Theory o E’s neg. charge (-) and they repel each other 

o E’s are arranged about central atom in a way to minimize  those repulsions. 

Molecular geometry—describes the relative positions of atoms in a  molecule.


Valence Theory and Hybrid Orbitals 

???? A chemical bond forms when atomic orbitals of atoms overlap.

Atomic Orbital: an expected region of electron density around an atom  based on a solution to the Schrodinger Wave function.

Hybridization: atomic orbitals produce hybrid orbitals.

The total # of orbitals available for forming  

bonds does not change—a new set is simply  


Linear sp hybrids: the two hybrid orbitals formed by the mixture of  one s-orbital and one p orbital.

Trigonal sp^2 hybrids: the three hybrid orbitals formed by the  mixture of one s and two p orbitals.

Tetrahedral sp^3 hybrids: the four hybrid orbitals formed by the  

mixture of one s orbital three p orbitals.

Hybrid orbitals 

Shortcut to determining hybridization of an atom in a molecule: 

▪ Look @ the atom 

▪ Count the # of atoms connected to the atom in question 

(not bonds: ATOMS). 

▪ Count the # of lone pairs attached to it 

Add these together: 

If it’s 4????sp^3

If it’s 3????sp^2

If it’s 2????sp

Formaldehyde pentane 


Compound bonds lone pairs geometry hybridization 

NH3 3 1 tetrahedral sp^3 4

SO3 3 0 trigonal SP^2 3


CO2 2 0 linear sp 2

• Chapter 5 

sp linear sp^3d Trigonal Bipyramidal sp^2 Trigonal Planar sp^3d^2 octahedral sp^3 Tetrahedral

Trigonal pyramidal

Bent seesaw/distorted tetra T-shaped square pyramid Square Planar

For the following molecules: 

o Determine a Lewis dot diagram 

o Determine the molecular geometry at each central atom o Determine bond angles



SeO2 GaH3 

Trigonal bipyramidal 72O 

Trigonal pyramidal




Trigonal Planar



SiO4-4 TeF6 








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