Chemistry Quiz #4
What are valence shell electron pair repulsion (VSEPR) theories?
(VSEPR) can be used to predict the spaes of molecules. VSEPR theory is based on the idea that electron groups- Lone pairs, single bonds, multiple bonds repel each other.
What is the geometry of CH4?
CH4 has a tetrahedral geometry with bond angles of 109.5°.
Steps on how to write Lewis Structures:
2.) Calculate the total number of electrons for the Lewis Structure by summing the valence electrons of each atom in the molecule.
Writing ions for Lewis Structures:
2.) If you are writing a Lewis Structure for a polyatomic ion, the charge of the ion must be considered when calculating the total number of electrons. Add one electron for each (-) charge and subtract for each (+) charge.
Resonance Structures ex's
2.) We then sum the valence electrons: O = 6(2) =12 e⁻ + S= 6 e⁻ 12 e⁻+ 6e⁻=18e⁻
What are exceptions to the octet rule?
NO which has 11 electrons.
What is an ionic bond?
An ionic bond forms when the electrons are transferred.
What is a chemical bond?
atoms with incomplete orbitals that react with other atoms in such a way that each partner completes its valence shell
H2CO what is its Lewis Structure?
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What are some exceptions to the octet rule?
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What is the Lewis Structure for CO2
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What is the Lewis structure of CH4?
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Write the Lewis Structure for NH4⁺
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Ex's of some resonance sturctures SO2
1.) We begin with the skeletal structure: O S O
Steps on how to write Lewis Structures:
1.) Write the correct skeletal structure for the molecule. Ex. H20 it must be written as H O H. Having oxygen as the central atom and the hydrogen as the terminal atoms.
Steps on how to write Lewis Structures:
3.) Distribute the electrons among the atoms, giving octets (or duets for hydrogen) to as many atoms as possible. Begin by placing two electrons between each pair of the atoms. The bonding electrons.
Resonance structures SO2
3.) We next place our bonding pairs two electrons between each pair of atoms O: S: O (4 of 18 electrons used).
Resonance structures for SO2
4.) Distribute remaining electrons, first to terminal atoms. Then, finally to central atoms.
Steps on how to write Lewis Structures:
4.) If any atoms lack an octet, form double or triple bonds as necessary to give them octets. Do this by moving lone electron pairs from terminal atoms into the bonding region with the central atom.
What is an octet?
8 dots is an octet. These are atoms with 8 valence electrons in an atom and are particularly stable.
What is a chemical bond?
A chemical bond involves the sharing or transfer of electrons to attain stable electron configurations for the bonding atoms.
What is a covalent bond?
A convalent bond is formed when the electrons are shared.
What is a duet?
A duet is two paired dots a (duet). For example He: or 1s^2.
Repulsion theory
The (VSEPR) the repulsion between the negative charges of electron groups on the central atoms determines the geometry of the molecule. For ex. CO2
What is the Lewis structure also referred to?
The Lewis structure is also a dot structure.
What is the Lewis Structure of Oxygen O
The Lewis structure of Oxygen has 6 valence electrons. So, the symbol O is surrounded by two dots on the top, r-side, one on the bottom and one of the l-side of the symbol.
What is the Lewis Theory?
The Lewis theory is named after G.N. Lewis (1875-1946), the American chemist who developed it.
The geometry of CO2 is determined by the repulsion between the two electron groups (the two double bonds) on the central carbon atom.
The geometry for CO2 is linear and it results is 180°.
What is the geometry of this Lewis Structure?
The geometry of H2CO is trigonal planar geometry.
What is the molecular geometry of CH4?
The molecular geometry of CH4 is trigonal pyramidal.
What is the total number of electrons in the Lewis Structure of OH⁻
The total number of electrons for OH⁻ is has 8 electrons; O 6 e⁻ and one from hydrogen, and one from the negative charge. 6+1+1 = 8 e⁻
What is the angle of trigonal planar geometry?
Trigonal planar geometry is 120°.
What are resonance structures?
Two or more non-identical Lewis structures for the same molecule. The molecules are represented with a ↔ between them.
What is the octet rule?
When atoms combine, stability is achieved with 8 valence electrons
What are bonding theories?
valence electron theory (vsepr and lewis structures), valence bond method (hybridization), and molecular orbital theory (molecular bonds)