Chapter 10 - Chemical Bonding
What is the Lewis Dot structure of C?
* * C* *
What is the Lewis Dot structure of B?
* *B*
What is the Lewis Dot structure of N?
* *N** *
What is the Lewis Dot structure of F?
** **F** *
What is the Lewis Dot structure of Ne?
** **Ne** **
What is the Lewis Dot structure of O?
** *O** *
What is the Lewis Dot structure of Be?
*Be*
What is a tetrahedral molecule shape?
The molecular geometrical shape of a molecule containing four electron groups (four bonding groups and no lone pairs)
What is the trigonal pyramidal molecule shape?
The molecular geometrical shape of a molecule containing four electron groups, three bonding groups and one lone pair.
What is in ionic compound?
An ionic compound the chemical bonding of a cation and an anion. A cation is formed when a metal loses an electron. A anion is formed when a nonmetal gains an electron.
How do you determine if a molecule is polar?
Determine if the molecule contains polar bonds. Determine whether the polar bonds add together to form a net dipole.
Is NH3 polar?
Draw the Lewis Dot Structure H I H--N--H ** The geometry of NH3 is trigonal pyramidal. NH3 is polar.
What is a molecular compound?
A molecular compound are created when a nonmetal bonds with another nonmetal. Molecular compounds contain covalent bonds in which electrons are shared between atoms rather than transferred.
What is a nonpolar molecule?
A molecule that does not have a dipole moment.
What is a polar molecule?
A molecule with polar bonds that add together to create a net dipole moment. A molecule with polar bonds that add together - they do not cancel each other - to form a dipole moment.
Write the Lewis Dot structure of the compound MgO.
Mg has 2 valence electrons. O has 6 valence electrons Mg loses two electrons (cation) and O gains two electrons (anion) ** Mg^2+[**O**]^2- **
What is molecular geometry?
Molecular geometry is the geometrical arrangement of the atoms.
Which two species have the same number of lone electron pairs in their Lewis structure? a) H2O and H3O+ b) NH3 and H3O+ c) NH3 and CH4 d) NH3 and NH4+
B) NH3 and H3O+ - Both have one lone pair of electrons.
Use the Lewis model to predict the formula of the compound that forms between calcium and chlorine.
Ca has 2 valence electrons. Cl has 7 valence electrons. ** *Ca* **Cl** * CaCl ** ** [**Cl**]-Ca^2+[**Cl**]- ** ** Therefore the formula is CaCl2
Write the Lewis structure for ClO- ion.
Cl O Valence Electrons: Cl = 7 valence electrons O = 6 valence electrons * Add one electron for negative ion 7 + 6 + 1 = 14 valence electrons ** ** [**Cl---O**]- (6 loan pairs around both Cl & O) ** **
Is the bond formed between N and Cl pure covalent, polar covalent or ionic?
N Electronegativity = 3.0 Cl Electronegativity = 3.0 Difference = 0 = Pure Covalent Bond
What is the Lewis structure of phosphorus (P).
P has 5 valence electrons * *K** *
What is the Lewis Model?
The Lewis Model was named after G. N. Lewis. In this model electrons are represented as dots and draw dot structures or Lewis structures to represent molecules.
What are exceptions to the Octet Rule?
It is impossible to write good Lewis structures for molecules with odd numbers of electrons, yet some of these molecules exist in nature. Another significant exception to the octet rule is boron which tends to form compounds with only 6 electrons around B, rather than 8. Molecules such as SF6 and PCl5 have more than 8 electrons around a central atoms in their Lewis structures. These are referred to as expanded octets.
What is the Lewis Dot structure of KCl?
K has 1 valence electron. Cl has 7 valence electrons K loses it electron (cation) and Cl gains an electron (anion) ** K+[**Cl**]- **
How is the Lewis structure for Polyatomic Ions written?
Lewis structures for polyatomic ions are written by following the same procedure, but we pay special attention to the charge of the ion when calculating the number of electrons for the Lewis structure. Add one electron for each negative charge. Subtract on electron for each positive charge.
What is the Lewis Dot structure of Li?
Li*
Write the Lewis structure of Mg?
Mg has 2 valence electrons. * Mg *
Is the bond formed between N and O pure covalent, polar covalent or ionic?
N Electronegativity = 3.0 O Electronegativity = 3.5 Difference = 0.5 = Polar Covalent Bond
Write the Lewis Dot structure of the compound NaBr.
Na has one valence electron. Br has 7 valence electrons Na loses an electron (cation) and Br gains and electron (anion) ** Na+[**Br**]- **
Can Lewis structures be written for an odd number of valence electrons?
No, it is impossible to write good Lewis structures for molecules with odd numbers of electrons, yet some of these molecules exist in nature.
Write the Lewis structure for H2CO
O H C H Valence Electrons: O = 6 valence electrons H = 1 valence electron C = 4 valence electron 6+ 2*1 + 4 = 12 valence electrons ** O ** II H-C-H (two lone pairs around the O)
Write the Lewis structure for NO3-. Include resonance structures.
O O N O Valence Electrons: O = 6*3 = 18 valence electrons N = 5 Valence electrons Add a valence electron for the negative ion NO3- = 18 + 5 + 1 = 24 valence electrons
What is the total number of electrons in the Lewis structure of OH-? a) 6 b) 7 c) 8 d) 9
O = 6 valence electrons H = 1 valence electron Add one for the negative charge = Total = 8 valence c) 8
Which two elements have the most similar Lewis Structures? a) C and Si b) O and P c) Li and F d) S and Br
a) C and Si - They have the same number of valence electrons. (4 valence electrons)
Is the bond formed between each pair of atoms pure covalent, polar covalent, or ionic? a) I and I b) Cs and Br c) P and O
a) I and I - Pure Covalent b) Cs and Br - Ionic c) P and O - Polar Covalent
Write the Lewis Dot structure for each ionic compound. a) NaF b) CaO c) SrBr2 d) K2O
a) NaF Na has 1 valence electron. F has 7 valence electrons. ** Na+[**F**]- ** b) CaO Ca has 2 valence electrons. O has 6 valence electrons. ** Ca^2+[**O**]-2 ** c) SrBr2 Sr has 2 valence electrons. Br has 7 valence electrons. ** ** [**Br**]-Sr^2+ [**Br**]- ** ** d) K2O K has 1 valence electron. O has 6 valence electrons. ** K+[**O**]^2-K+ **
What the electronegativity difference for a pure covalent bond?
0-0.4 (zero) Example Cl2
What the electronegativity difference for a polar covalent bond?
0.4 - 2.0 (intermediate) Example HF
What are the steps to write the Lewis structure for covalent compounds?
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 electrons among the atoms, giving octets (or duets for hydrogen) to as many as possible. 4) If any atoms lack an octet, form double or triple bonds as necessary to give them octets.
What the electronegativity difference for a ionic bond?
2.0+ (Large) Example NaCl
What is a bonding pair of electrons?
A bonding pair of electrons are electrons that are shared between atoms. Bonding pair electrons are often represented by dashes to emphasize that they are a chemical bond. H-O-H (two lone pairs one above the O and one below the O)
What is a bonding theory?
A bonding theory are models that predict how atoms bond together to form molecules.
What is a chemical bond?
A chemical bond involves sharing or transfer of electrons to attain stable electron configurations for the bonding atoms. In chemical bonding, atoms transfer or share electrons to obtain outer shells with 8 electrons.
What is a covalent bond?
A chemical bond where electrons are shared.
What is an ionic bond?
A chemical bond where electrons are transferred.
What is a triple bond?
A chemical bond where three electron pairs are shared between two atoms. In general, triple bonds are shorter and stronger than double bonds.
What is a double bond?
A chemical bond where two electrons are shared between two atoms. In general, double bonds are shorter and stronger than single bonds. In the Lewis model, atoms can share more than one electron pair to attain and octet.
What is a polar covalent bond?
A covalent bond between atoms of different electronegativities. Polar covalent bonds have a dipole moment. Covalent bonds that have a dipole moment.
What is lone pair of electrons?
A lone pair of electrons are electrons that are only on one atom. They are also referred to as non-bonding electrons.
What is a dipole moment?
A measure of the separation of charge in a bond or in a molecule.
What is a stable configuration?
A stable configuration usually consists of 8 electrons in the outermost valence shell. This observation leads to the octet rule.
What is the Valence Shell Electron Pair Repulsion (VSEPR) Theory?
A theory that allows prediction of the shapes of molecules based on the idea that electrons - either as lone pairs or as bonding pairs - repel one another.
What is a terminal atom?
An atom that is located at the end of a molecule or chain. Hydrogen atoms are always terminal. Many molecules tend to be symmetrical.
Write the Lewis structure for CN-
C N Valence Electrons: C = 4 valence electrons N = 5 valence electrons 5 + 4 = 9 valence electrons * add one valence electron for the negative charge = 10 [**C (triple bond) N**]- (a lone pair on the C and N
Write the Lewis structure for CO
C O Valence electrons C = 4 valence electrons O = 6 valence electrons 4 + 6 = 10 valence electrons C(triple bond) O (two lone pairs on the C & O) **C(triple bond)O**
What are the electron groups, bonding groups, lone pairs and angle for the linear shape?
Electron Groups - 2 Bonding Groups - 2 Lone Pairs - 0 Angle Between Electron Groups - 180 degrees Example: O==C==O
What are the electron groups, bonding groups, lone pairs and angle for the trigonal planar shape?
Electron Groups - 3 Bonding Groups - 3 Lone Pairs - 0 Angle Between Electron Groups - 120 degrees O II Example: H--C--H
What are the electron groups, bonding groups, lone pairs and angle for tetrahedral shape?
Electron Groups - 4 Bonding Groups - 4 Lone Pairs - 0 Angle Between Electron Groups - 109.5 degrees H I H--C---H I H
What is electron geometry?
Electron geometry is the geometrical arrangement of the electron groups.
What are electron groups?
Electron groups are lone pairs, single bonds or multiple bonds.
Write the Lewis structure for CCl4.
Following symmetry guidelines Cl Cl C Cl Cl The total number of valence electrons for the Lewis structure. Cl valence electrons = 7 C valence electrons = 4 4*7 + 4 = 32 valence electrons Cl I Cl-C- Cl (there are 3 lone pairs around each of the Cl) I Cl
Write the Lewis structure for CO2.
Following the symmetry guideline write: O C O The total number of electrons for Lewis structure. C valence electrons = 4 O valence electrons = 6 4 + 2*6 = 16 valence electrons. O=C=O (with two lone pairs on each of the Oxygen atoms)
Write the Lewis structure for the NH4+ ion.
H H N H H Valence Electrons: H = 1 = 4*1 = 4 valence electrons N = 5 valence electrons * Subtract one valence electron for positive charge 4 + 5 - 1 = 8 valence electrons H ** H[**N**]+ ** H H I H--N--H I H
How are covalent bonds represented in the Lewis Model?
In the Lewis Model, we represent covalent bonding by allowing neighboring atoms to share some of their valence electrons in order to attain octets (or duets for hydrogen). Molecular compounds contain covalent bonds in which electrons are shared between atoms rather than transferred.
In water, how are electrons shared?
In water, hydrogen and oxygen share their electrons so that each hydrogen atom gets a duet and the oxygen atom gets an octet.
How many bonding electrons are in the Lewis structure of O2? a) 2 b) 4 c) 6
O has 6 valence electrons. b) 4 The Lewis structure of O2 has one double bond that contains 4 electrons (all of them bonding electrons); Therefore the number of bonding electrons is four.
Is the bond formed between Sr adn F pure covalent, polar covalent or ionic?
Sr Electronegativity = 1.0 F Electronegativity = 4.0 Difference = 3.0 = Ionic Bond
What are the notations for bonds?
Straight Line = Bond in plane of paper Hashed Lines = Bond projecting into paper Wedge = Bond projecting out of the paper
What is electronegativity?
The ability of an element to attract electrons within a covalent bond.
What is the trigonal planar molecule shape?
The molecular geometrical shape of a molecule containing three electron pairs (three bonding groups and no lone pairs)
What is a linear molecule shape?
The molecular geometrical shape of a molecule containing two electron groups (two bonding groups and no lone pairs).
What is a duet?
The number of electrons around He with stable Lewis Structures which is 2.
What is an octet?
The number of electrons around atoms with stable Lewis Structures which is 8.
What is the octet rule?
The octet rule: In chemical bonding, atoms transfer or share electrons to obtain outer shells with 8 electrons. The octet rule generally applies to all main-group elements except for hydrogen, lithium, and beryllium. Each of these elements achieves stability when it has two electrons (a duet) in its outermost shell.
How are polyatomic ions written in the Lewis structure?
The structure for a polyatomic ion within brackets and write the charge of the ion in the upper right corner.
Explain the Lewis Structure or Dot Structure.
The valence electrons of main-group elements are represented as dots surrounding they symbol of the element. Each dot represents a valence electron. The Lewis structure allows us to easily see the number of valence electrons in an atom. The exact location of dots is not critical, here we fill in the dots singly first and then pair them.
What is a resonance structure?
Two or more Lewis structures that are necessary to describe the bonding in a molecule or ion. When writing Lewis structures, some molecules can be written in more than one good Lewis structure.
Which nonmetal forms an ionic compound with aluminum that has the formula Al2X3 (X represents the nonmetal)? a) Cl b) S c) N d) C
b) S Aluminum must lose its 3 valence electrons to obtain an octet. Sulfur must gain 2 electrons to obtain an octet. Therefore, two Al atoms are required for every 3 S atoms.
Which nonmetal forms an ionic compound with aluminum that has the formula Al2X3 (where X represents the nonmetal)? a) Cl b) S c) N d) C
b) S - Sulfur. Aluminum must lose its 3 valence electrons to obtain and octect. Sulfur must gain 2 electrons to obtain an octect. Therefore, two Al atoms are required for every 3 S atoms.
Which condition necessarily leads to a molecular geometry that is identical to the electron geometry? a) The presence of a double bond between the central atom and a terminal atom. b) The presence of two or more identical atoms bonded to the central atom. c) The presence of one or more lone pairs on the central atom. d) The absence of any lone pairs on the central atom.
d) The absence of any lone pairs on the central atom. If there are no loan pairs on the central atom, all of its valence electrons are involved in bonds, so the molecular geometry must be the same as the electron geometry.
