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Questions and Answers
In the second period of the periodic table, it is possible to exceed 8 electrons in the valence shell, but an atom may not have less than 8.
In the second period of the periodic table, it is possible to exceed 8 electrons in the valence shell, but an atom may not have less than 8.
False (B)
Any molecule with an odd number of valence electrons cannot give a full octet to each of its component atoms.
Any molecule with an odd number of valence electrons cannot give a full octet to each of its component atoms.
True (A)
An atom X is neutral and has 3 valence electrons. Which of the following atoms could X be?
An atom X is neutral and has 3 valence electrons. Which of the following atoms could X be?
- P
- Ge
- Sr
- Ga (correct)
How many valence electrons does Silicon have?
How many valence electrons does Silicon have?
How many valence electrons does Fluorine have?
How many valence electrons does Fluorine have?
How many total valence electrons does SiF4 have?
How many total valence electrons does SiF4 have?
Which should be the central atom for SiF4 and why?
Which should be the central atom for SiF4 and why?
How do you assign formal charges to atoms in a molecule?
How do you assign formal charges to atoms in a molecule?
In a hypothetical molecule, a Nitrogen has two sets of lone pair electrons and two covalent bonds. What would its formal charge be?
In a hypothetical molecule, a Nitrogen has two sets of lone pair electrons and two covalent bonds. What would its formal charge be?
In calculating formal charges, a double bond is treated exactly the same as a single bond when doing calculations.
In calculating formal charges, a double bond is treated exactly the same as a single bond when doing calculations.
Nitrate has several resonance structures. What does this mean?
Nitrate has several resonance structures. What does this mean?
Which of the following is NOT one of the main tenets of VSEPR theory?
Which of the following is NOT one of the main tenets of VSEPR theory?
What is the name of the number of atoms that will bond to the central atoms, and is often used when describing lattices?
What is the name of the number of atoms that will bond to the central atoms, and is often used when describing lattices?
What is the purpose of VSEPR?
What is the purpose of VSEPR?
In VSEPR theory, a double bond is treated exactly the same as a single bond when determining electron and molecular shapes.
In VSEPR theory, a double bond is treated exactly the same as a single bond when determining electron and molecular shapes.
What is the difference between electron geometry and molecular geometry?
What is the difference between electron geometry and molecular geometry?
How many 'electron clouds' are surrounding the central atom of BeCl2?
How many 'electron clouds' are surrounding the central atom of BeCl2?
What is the electron geometry of BeCl2? Molecular geometry?
What is the electron geometry of BeCl2? Molecular geometry?
Why doesn't Chlorine share its lone pair of electrons with Beryllium in BeCl2?
Why doesn't Chlorine share its lone pair of electrons with Beryllium in BeCl2?
What is the electron geometry of BF3? Molecular geometry?
What is the electron geometry of BF3? Molecular geometry?
What is the electron geometry of CH4? Molecular geometry?
What is the electron geometry of CH4? Molecular geometry?
For a tetrahedral compound, which of the following is the ideal bond angle (in degrees)?
For a tetrahedral compound, which of the following is the ideal bond angle (in degrees)?
What is the electron geometry of H2O? Molecular geometry?
What is the electron geometry of H2O? Molecular geometry?
What is the electron geometry of NH3? Molecular geometry?
What is the electron geometry of NH3? Molecular geometry?
What is the electron geometry of CO2? Molecular geometry?
What is the electron geometry of CO2? Molecular geometry?
What is the electron geometry of O3? Molecular geometry?
What is the electron geometry of O3? Molecular geometry?
What is the electron geometry of Carbonate? Molecular geometry?
What is the electron geometry of Carbonate? Molecular geometry?
What is the electron geometry of Sulfate? Molecular geometry?
What is the electron geometry of Sulfate? Molecular geometry?
Study Notes
Octet Rule and Valence Electrons
- In the second period, atoms can have fewer than 8 valence electrons but not more than 8, following the octet rule.
- Odd number of valence electrons in a molecule prevents giving a full octet to each atom.
Identifying Atoms and Valence Electrons
- Gallium (Ga) is a neutral atom with 3 valence electrons, being part of group 3A.
- Silicon possesses 4 valence electrons, while Fluorine has 7 valence electrons.
Calculating Total Valence Electrons
- For SiF4, total valence electrons calculated as (7x4) + 4 = 32.
Central Atoms and Dot Structures
- In SiF4, Silicon is the central atom as it is less electronegative than Fluorine.
- Carbon typically forms double bonds to satisfy the octet rule when required.
Formal Charges and Stability
- Formal charge is calculated as: Valence electrons - (Lone pair electrons + 1/2 shared electrons).
- Resonance structures indicate that extra electrons are shared among bonds concurrently.
VSEPR Theory Fundamentals
- VSEPR theory predicts molecular shapes based on electron pair repulsion.
- Electron clouds around a central atom determine the geometry; lone pairs exert greater repulsion than bonding pairs.
Electron and Molecular Geometry
- Electron geometry refers to the arrangement of electron clouds; molecular geometry describes the arrangement of bonded atoms.
- Common geometries include linear, trigonal planar, tetrahedral, bent/angular, and trigonal pyramidal.
Bond Angles and Electron Clouds
- Ideal bond angles: tetrahedral (109.5 degrees), trigonal planar (120 degrees), with each geometry having distinctive arrangements.
- BeCl2 has linear electron and molecular geometries, while NH3 is tetrahedral in electron geometry but trigonal pyramidal in molecular geometry due to lone pairs.
Resonance Structures
- Nitrate exhibits resonance, representing multiple possible structures while actually sharing electrons throughout.
Key Differentiations
- Coordination number describes how many atoms bond to a central atom, critical in lattice illustrations.
- Not all molecules adhere strictly to ideal bond angles due to varying repulsion from lone pairs.
Summary of Molecular Geometries
- Carbonate and sulfate both exhibit trigonal planar and tetrahedral geometries, respectively.
- Understanding these shapes and the underlying principles is crucial for predicting molecular behavior and reactivity.
Studying That Suits You
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Description
Test your knowledge on dot structures and the VSEPR theory in this flashcard quiz. Learn about the concepts of the octet rule and electron configurations in the periodic table. This lesson covers essential foundational topics in chemistry for better understanding.
