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CEM 141 Chapter 3 Test Questions And Answers Rated A+ New Update Assured Satisfaction
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CEM 141 Chapter 3 Test# of atomic orbitals in= # of hybrid orbitals out - ANS-Hybrid Orbitals
1. ability of an element to attract electrons to itself in a bond
a. atom with high effective nuclear charge attracts its own valence electrons strongly and it
attracts electrons from other atoms in bonds
2. Depends on effective nuclear charge
3. trend is same as effective nuclear charge (except for noble gases)
a. dec. down a group because atom gets bigger
b. increases across a row because valence electrons are closer to nucleus -
ANS-Electronegativity
1. Absorption of a photon will promote an electron to a higher energy level
2. It immediately falls back down-emitting a photon-the metal shines
3. the metal interacts with light of many wavelengths, so the metal appears white or colorless
(silvery)
a. metals are shiny because photons of many wavelengths are absorbed and then emitted -
ANS-Why are metals shiny? (properties of metals)
1. all made up of carbon entirely but connectivity of atoms is different for each
a. diamond
b. graphite - ANS-Allotropes of Carbon
1. all of these molecules are polar and can participate in H-bonding, and all have LDFs but H2O
is a liquid at room temp while NH3 and HF are gases, so H2O has highest BP (100°C) -
ANS-Which would you predict to have the highest BP: NH3, H2O, HF?
1. atomic orbitals "hybridize" (mix up) to form bonding orbitals that then combine with orbitals
from other atoms to form a bond
2. to form 4 bonds- carbon hybridizes the 4 orbitals that are used for bonding
3. since one s and three p orbitals combine, we call them sp^3 orbitals
4. they naturally assume a tetrahedral shape
5. when hybrid orbitals combine there is a large gap between the bonding and anti bonding
molecular orbitals - ANS-Bonding in Diamond (Valence Bond Model)
1. atomic orbitals can combine constructively to form a molecular orbital of lower energy (in
phase)
2. atomic orbitals can combine destructively to form a molecular orbital of higher energy (out of
phase)
3. combine n atomic orbitals--> n molecular orbitals
4. Bonding and Anti-bonding orbitals
, a. both are in the same place of space, just at different energies - ANS-Molecular Orbital Theory
1. atomic orbitals combine to form an equal number of molecular orbitals
2. each orbital can contain up to 2 electrons
3. electrons in bonding orbitals stabilize the system
4. electrons in anti bonding orbital make it less stable
5. electrons are delocalized - ANS-Bonding in Molecular Orbitals
1. atomic orbitals overlap to form a bond
2. the greater the overlap, the stronger the bond
3. each bond is made up of 2 electrons
4. electrons are localized in the bond - ANS-Valence Bonds
1. atomic orbitals overlap to form bonds
2. bonds are often shown as sticks (H-H)
a. consider bonds to be localized between 2 bonded atoms (not like in MO theory) -
ANS-Valence Bond Theory
1. bonding in Fe is a like a network
a. valence electrons are delocalized and hold the core electrons together
b. to break this you would need a lot of energy, which explains the high MP - ANS-Explain how
bonding leads to high MP in iron (Fe)
1. both caused by forces of attraction
2. both require energy to overcome - ANS-Similarities between Covalent Bonds and Molecular
Interactions
1. C is sp hybridized
2. Triple bonds consists of:
a. one sigma bond (sp-sp overlap)
b. two pi bonds (sideways p-p overlap) - ANS-Triple Bonds
1. calculate total number of valence electrons
a. use group number for each element
b. for cations: remove n electrons
c. for anions: add n electrons
2. write skeleton structure (look at way formula is written)
a. use the valence (valence= 8- # of valence electrons)
3. make 2 electrons for each bond
4. make sure each atom (except H and B) has 8 electrons by adding lone pairs
5. if there are not enough electrons form multiple bonds - ANS-Rules for drawing Lewis
Structure
1. carbon forms four bonds
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