Pre-Lecture Chapter 10
Write the Lewis structure for CO.
(Pa unsa daw tagnaa ) :C[3 kabuok lines]O:
1. What are resonance structures? 2. Why are they necessary?
1. Resonance structures of molecules are the AVERAGE of one or more EQUIVALENT Lewis structures and represent the TRUE structure of the molecule. 2. Resonance structures are needed because the EQUIVALENT Lewis structures ARE NOT an accurate representation of the molecule.
What is the procedure for writing a covalent Lewis structure?
1. Write the correct SKELETAL STRUCTURE for the molecule. 2. Calculate the total NUMBER OF ELECTRONS for the Lewis structure by summing the VALENCE ELECTRONS of each atom in the molecule. 3. Distribute the NUMBER OF ELECTRONS among the atoms, giving octet(s) (or duet(s) for hydrogen) to as many atoms as possible. 4. If an atom lacks a(n) octet(s), form double or triple bonds, as needed.
What is the difference between lone pair and bonding pair electrons?
A pair of electrons shared between two atom(s) is called a bonding pair. A pair of electrons located only on one atom(s) is called a lone pair.
What is a polar covalent bond?
A polar covalent bond is a covalent bond in which electrons are not equally shared between the two atoms.
What is the difference between ionic bonding and covalent bonding?
A(n) IONIC bond is formed as a result of the TRANSFER of electrons from one atom (or GROUP of atoms) to another. The OPPOSITELY charged particles that are formed are then attracted to each other. A(n) COVALENT bond exists when the electrons are SHARED between TWO atoms.
How do you determine the number of electrons that go into the Lewis structure of a molecule?
Add up the VALENCE ELECTRONS from each atom that is forming the molecule.
In the Lewis model, what is an octet? What is a duet? What is a chemical bond?
An octet is an atom that contains 8valence electrons. A duet is a pair of valence electrons . A chemical bond is the sharing or transfer of electrons to form a stable electron configuration.
Which atom has a Lewis structure with an octet?
Ar
What is electronegativity?
Electronegativity is the ability of an atom to attract electrons toward itself in a covalent bond.
Which scientist developed a model that can be used to predict the structure of a molecule?
G.N. Lewis
If a molecule has polar bonds, is the molecule itself polar?
If a molecule has polar bonds, the molecule can be either polar or nonpolar.
What is the difference between electron geometry and molecular geometry in VSEPR theory?
In the VSEPR theory, the electron geometry refers to the shape of the electron pairs. The molecular geometry is concerned only with the shape of the molecule itself, which means that only the placement of atoms as a result of the electron geometry is taken into account.
Which of the following Lewis structures of ozone, O3, is correct?
O=O-O (bente muna beh para ma gets mo)
Which of the following is an exception to the octet rule? Ignore that hydrogen has a duet.
SF6
How do you determine the number of electrons that go into the Lewis structure of a polyatomic ion?
Sum the VALENCE ELECTRONS from each ATOM that is forming the polyatomic ion as you did for molecules, but add 1 electron for every -1 charge and subtract 1 electron for every +1 charge.
Which of the following describes a scenario in which the molecular geometry would have the smallest bond angle(s)?
TWO bonding domains (or bonding pairs) and TWO nonbonding domains (or lone pairs)
How can the Lewis model be used to determine the formula of ionic compounds? You may explain this with an example.
The Lewis structure for potassium has 1 VALENCE ELECTRON, while the Lewis structure for monoatomic chlorine has 7 VALENCE ELECTRON. From these structures we can determine that if potassium gives up the 1 VALENCE ELECTRON to chlorine, K + and C l − ions are formed. Therefore, the formula of the compound must be KCl.
Why does the octet rule have exceptions? List some examples.
The exceptions to the octet rule may refer to compounds that have ODD numbers of valence electrons. For example, BORON compounds tend to form with only 6 valence electrons, and some compounds that have more than 8 valence electrons.
Predict the molecular geometry of ClNO (N is the central atom).
The molecular geometry of ClNO is bent
Why?
The two requirements of a polar molecule are: the molecule must have polar bonds and the polar bonds must be distributed asymmetrically, otherwise they cancel out.
Explain how VSEPR theory predicts the shapes of molecules.
The valence shell ELECTRON PAIR repulsion (VSEPR) theory states that molecular shape is dictated by the fact that ELECTRON PAIRS REPEL each other and try to assume an optimum MAXIMUM distance from each other.
What happens if you try to mix a polar liquid with a nonpolar one?
They will separate to form two distinct regions.
In a Lewis structure, a dash drawn between two atoms represents _______________.
a shared electron pair
Which of the following molecule is polar?
h-o-h (hulaan mo saan hehe)
Which of the following atoms would most likely be terminal in a Lewis structure?
hydrogen
If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for two electron groups?
linear
How many valence electrons does it have?
n=8
Which of the following molecules has a trigonal planar shape?
o h-c-h (penge jowa para masagot mo 😉)
If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for four electron groups?
tetrahedral
What is the electron geometry of PF3?
tetrahedral
If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for three electron groups?
trigonal planar
What is the molecular geometry of SO32−?
trigonal pyramidal
Which of the following description best describes the type of electrons used to write a Lewis structure?
valence
Which of the following symbols are used to illustrate commonalities between two or more resonance structures?
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