Ionic, Covalent, and Metallic Bonds
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Questions and Answers

Explain why water molecules are effective at dissolving ionic substances, even though water itself doesn't have ionic bonds.

Water molecules are polar, possessing partially positive and partially negative regions. These regions interact with the positive and negative ions of the ionic substance, effectively pulling them apart and dispersing them in the water.

Describe the role of lone pairs of electrons in determining molecular shape, and why they are considered when predicting geometry.

Lone pairs repel other electron pairs (both bonding and lone pairs) more strongly than bonding pairs do. This repulsion influences the bond angles and overall shape of the molecule. Although lone pairs aren't 'visible' as atoms, their repulsive effect distorts the shape.

How do you determine if a molecule is polar or nonpolar based on its symmetry and charge distribution?

A molecule is polar if its electron distribution is asymmetrical, leading to a net dipole moment. A molecule is nonpolar if it is symmetrical, meaning the bond dipoles cancel each other out, resulting in no net dipole moment.

When determining the geometry of a molecule, what is the difference between 'molecular geometry' and 'electron pair geometry'?

<p>Electron pair geometry considers all electron groups (bonding and lone pairs) around the central atom, while molecular geometry only considers the arrangement of the atoms (bonded pairs).</p> Signup and view all the answers

Predict the molecular shape of a molecule with two bonded pairs of electrons and one lone pair on the central atom. Name the shape and briefly explain why it adopts that specific arrangement.

<p>The molecular shape is bent. The two bonding pairs and one lone pair arrange themselves to minimize repulsion, resulting in a bent arrangement of the atoms.</p> Signup and view all the answers

A substance is composed of only carbon and hydrogen atoms bonded together. Is this substance classified as molecular, atomic, or ionic? Explain.

<p>It's molecular because it consists of only nonmetals (carbon and hydrogen) bonded together.</p> Signup and view all the answers

A solid is formed from repeating units of a single kind of atom. is this substance classified as molecular, atomic, or ionic? Explain.

<p>It's atomic because it consists of only a single element.</p> Signup and view all the answers

A compound is formed from sodium and chlorine atoms. is this substance classified as molecular, atomic, or ionic? Explain.

<p>It's ionic because it consists of a metal (sodium) and a nonmetal (chlorine) together.</p> Signup and view all the answers

Explain how the octet rule contributes to the formation of chemical bonds.

<p>Atoms 'want' a full outer shell to be more stable. The octet rule states that most atoms require eight electrons in their valence shell to achieve this stability. Atoms will form bonds by sharing, donating, or recieving electrons in order to meet the octet rule.</p> Signup and view all the answers

Describe the fundamental difference between ionic and covalent bonds, focusing on electron behavior.

<p>Ionic bonds involve the transfer of electrons from a metal to a nonmetal, creating ions. Alternatively, covalent bonds involve the sharing of electrons between two nonmetals.</p> Signup and view all the answers

How does the 'electron sea' model explain the properties of metallic bonds, such as conductivity?

<p>In metallic bonding, metal atoms release electrons into a 'sea' around positively charged metal ions. These delocalized electrons are free to move throughout the structure, facilitating electrical conductivity.</p> Signup and view all the answers

What is the significance of a 'lone pair' of electrons in VSEPR theory, and how does it affect molecular geometry?

<p>Lone pairs are non-bonding electron pairs that exert more repulsive force than bonding pairs. This repulsion affects the arrangement of atoms in a molecule, influencing its overall shape or geometry.</p> Signup and view all the answers

Explain why resonance structures are necessary to accurately represent the bonding in some molecules.

<p>Resonance structures are needed when a single Lewis structure cannot accurately depict the true electron distribution in a molecule. The actual structure is a hybrid or average of all possible resonance forms.</p> Signup and view all the answers

Outline the general steps for drawing a Lewis structure.

<p>First, determine the total number of valence electrons. Second, arrange the atoms, usually with the most singular atom in the center. Thrid, form bonds by distributing pairs of electrons between atoms. Finally, distribute remaining electrons to give each atom an octet, forming double or triple bonds if needed.</p> Signup and view all the answers

Describe what a polyatomic ion is, and provide an example.

<p>Polyatomic ions are groups of covalently bonded atoms that together have a net electrical charge. An example is the sulfate ion, $SO_4^{-2}$.</p> Signup and view all the answers

Explain the concept of expanded octets and why they occur in some molecules.

<p>Expanded octets occur when a central atom has more than eight electrons in its valence shell. This is possible for elements in period 3 and beyond because they can utilize their <em>d</em> orbitals for bonding.</p> Signup and view all the answers

Using the principles of VSEPR theory, predict the molecular geometry of $BeCl_2$.

<p>Beryllium has two bonding pairs and no lone pairs, which results in a linear molecular geometry based on VSEPR theory. The chlorine atoms are on opposite sides of the Beryllium, 180° apart.</p> Signup and view all the answers

How does electronegativity relate to bond polarity, and what type of bond is formed when there is a large electronegativity difference between two atoms?

<p>Electronegativity is a measure of an atom's ability to attract electrons in a bond. A large electronegativity difference between two atoms results in a polar bond, where electrons are unevenly shared.</p> Signup and view all the answers

Flashcards

Water as a Solvent

Water's polarity dissolves ionic substances despite lacking ionic bonds itself.

Central Atom

The central atom is the atom that forms the most bonds in a dot structure.

Bonded Pairs/Groups

Atoms attached to the central atom.

Lone Pairs/Groups

Lone pairs are valence electrons attached to the central atom but are not bonded to another atom.

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Electron Groups

The total number of bonding pairs and lone pairs around the central atom.

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Symmetrical Molecule

Ability of a molecule to be cut in half and be the same on both sides.

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Polar Molecule

A molecule with uneven charge distribution due to its asymmetrical shape.

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Bent Molecule

Molecular geometry when there is one lone pair and two bonded pairs

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Why do atoms bond?

Atoms bond to achieve a stable, full outer shell of electrons.

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How do atoms achieve stability?

Atoms 'donate', 'receive', or 'share' electrons to achieve stability.

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Octet Rule

The maximum number of electrons in an atom's outer shell is 8.

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What is an ion?

An atom that has gained or lost an electron, resulting in a charge.

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Ionic Bonding

Bonding that occurs when a metal atom donates electrons to a non-metal atom.

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Cation

A positively charged ion.

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Anion

A negatively charged ion.

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Covalent Bonding

Bonding that occurs when atoms share pairs of electrons.

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Polyatomic Ions

Charged entities composed of two or more covalently bonded atoms.

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Resonance Structures

Molecules that cannot be correctly represented by a single Lewis diagram; the actual structure is an average of all possibilities.

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Study Notes

  • Atoms bond to become more stable when they have full outer shells.
  • Donating, receiving, or sharing electrons allows atoms to achieve stability.
  • The Octet Rule dictates a maximum of 8 electrons in the outer shell.

Ions and Ionic Bonding

  • An ion is an atom that has lost or gained an electron.
  • Ionic bonding occurs when a metal atom donates one or more electrons to a non-metal atom.
    • The metal becomes more positive and is called a cation
    • The non-metal becomes more negative and is called an anion
    • The non-metal effectively transfers its electron(s) to the metal.

Covalent and Metallic Bonding

  • Covalent bonding occurs when atoms share pairs of electrons instead of giving and receiving.
    • The shared pair is included in the outer shell of both atoms.
    • Covalent bonding occurs between atoms of nonmetals.
  • Metallic bonds occur when atoms of metals give up electrons, forming a "sea" of electrons.
    • Positively charged atoms are bonded through their attraction to the negatively charged electrons.

Electron Dot Structures and Lewis Diagrams

  • Diagrams show valence electrons as dots.
  • To draw Lewis Diagrams:
    • Find the total number of valence electrons.
    • Arrange atoms, a singular atom is usually in the middle
    • Form bonds between atoms, each bond consisting of 2 electrons.
    • Distribute remaining electrons to give each atom an octet.
    • If there aren't enough electrons, form double or triple bonds.

Polyatomic Ions and Resonance Structures

  • Polyatomic ions are charged entities composed of two or more atoms that are covalently bonded together, collectively carrying a charge.
  • Some molecules can't be correctly represented by a single Lewis diagram and require resonance structures.
    • The actual structure is an average of all possible structures.
    • Possible structures are separated by a double-headed arrow.

Exceptions to the Octet Rule

  • Writing a good Lewis structure for molecules with odd numbers of electrons isn't possible, yet some of these molecules exist.
  • Boron tends to form compounds with only 6 electrons around it, rather than 8, is an exception to the octet rule.
  • Some molecules have more than 8 electrons around a central atom in their Lewis Structure, referred as expanded octets.

VSEPR Theory

  • Valence Shell Electron Pair Repulsion (VSEPR) theory explains how molecules and ions behave.
  • The basic procedure is:
    • Determine the central atom (lowest subscript and/or the atom capable of forming the most bonds).
    • Draw the electron dot structure and bar diagram.
    • Determine the molecular geometry using ALL electron pairs AND atoms around the central atom.
    • Modify the geometry to determine the molecular shape if non-bonding electron pairs exist by ignoring them, while leaving the atoms of bonded pairs where they are.
      • This is done because even if the electrons have no atom attached, these unbonded electron pairs still affect the shape of the structure.
  • Bonded pairs/groups: atoms attached to the central atom.
  • Lone pairs/groups: pairs of valence electrons attached to the lone pair, not bonded to a different atom.
  • Electron groups: the bonding pairs and lone pairs added together.
  • A molecular structure is symmetrical if it can be bisected in the middle and the halves are identical.
    • It is polar if it's nonsymmetrical, and nonpolar if it's symmetrical.
      • This is because one side would have a different charge than the other if the molecule is nonsymmetrical.
  • A bent molecule occurs when there's 1 lone pair and 2 bonded pairs.
  • Bonding groups and lone pairs determine a molecule's molecular geometry, or how the atoms arrange in the molecule.
  • The arrangement dictates the specific angle at which the atoms are separated.
  • A solid is molecular if it is exclusively nonmetals bonded together.
  • A solid is atomic if only containing a single element.
  • A solid is ionic if both metals and nonmetals are together.

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Chemical Bonding: Lewis Diagrams, VSEPR Theory - PDF

Description

Explore ionic bonds formed by electron transfer between metals and nonmetals, creating cations and anions. Learn about covalent bonds through electron sharing between nonmetals, and metallic bonds where metal atoms release electrons into a 'sea'. The octet rule dictates a maximum of 8 electrons in the outer shell.

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