Chapter 5.3 - Electrons and Bonding (Covalent Bonding) Flashcards
What is covalent bonding?
Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
In what types of substances does covalent bonding occur?
Covalent bonding occurs in:
- Non-metallic elements (e.g., O₂).
- Compounds of non-metallic elements (e.g., H₂O).
- Polyatomic ions (e.g., NH₄⁺).
What is the key feature of covalent bonding?
The key feature is the sharing of a pair of electrons between two atoms.
How is covalent bonding different from ionic bonding?
- Covalent bonding involves sharing electrons.
- Ionic bonding involves transfer of electrons to form separate ions.
What are the three types of covalent structures, and give an example for each?
- Small molecule: H₂.
- Giant covalent structure: SiO₂.
- Charged polyatomic ion: NH₄⁺.
How is a covalent bond formed?
A covalent bond is formed by the overlap of atomic orbitals, each containing one electron, resulting in a shared pair of electrons.
What attracts the shared electrons in a covalent bond?
The shared electrons are attracted to the nuclei of both bonding atoms.
How do covalent bonds affect the outer shells of atoms?
The bonded atoms often achieve an outer shell electron structure similar to the nearest noble gas.
How is a covalent bond localized?
The attraction is localized between the shared pair of electrons and the nuclei of the two bonded atoms, forming discrete molecules (e.g., H₂ or H₂O).
What is the smallest part of a covalent compound?
A molecule is the smallest part of a covalent compound that retains its chemical properties.
How are single covalent bonds represented?
- Dot-and-cross diagrams: Electrons are represented as dots (one atom) and crosses (the other atom).
- Displayed formula: Bonds are shown as lines between atoms, and lone pairs can be included.
What are lone pairs in a molecule?
Lone pairs are pairs of electrons not involved in bonding.
How many covalent bonds are typically formed by common elements?
Carbon: 4 bonds
Nitrogen: 3 bonds
Oxygen: 2 bonds
Hydrogen: 1 bond
Why does boron not follow the octet rule?
Boron has only three outer-shell electrons, forming compounds like BF₃ with 6 electrons around the boron atom.
How can elements like phosphorus, sulfur, and chlorine exceed the octet rule?
In Period 3, the n=3 shell can hold up to 18 electrons, allowing for expanded octets. For example:
SF₂: 2 bonds (2 unpaired electrons).
SF₄: 4 bonds (4 unpaired electrons).
SF₆: 6 bonds (6 unpaired electrons).
