Enlaces Quimicos
How Do Atoms and Molecules Bond?
Understanding Atomic Structure and Chemical Bonds
- The historical view of atoms depicted them as infinitely small, indivisible particles with features resembling hands or iron rings that allowed them to link together.
- A chemical bond is defined as the union between atoms formed by the transfer, sharing, or acceptance of electrons to achieve a stable structure, often guided by the octet rule.
- The octet rule states that atoms exchange electrons until they have eight in their outermost energy level, facilitating chemical bonding.
Ions and Ionic Bonds
- An atom becomes an ion when it gains or loses an electron; a positively charged ion (cation) has fewer electrons than protons, while a negatively charged ion (anion) has more.
- Ionic bonds occur when one atom loses electrons and another gains them; this typically happens between metals with few outer electrons and nonmetals with many.
- For example, sodium (Na), which has one electron in its outer shell, transfers this electron to chlorine (Cl), which needs one more to complete its octet. This results in Na+ and Cl− ions forming sodium chloride (table salt).
Characteristics of Ionic Compounds
- Ionic compounds are characterized by their crystalline structure, high melting and boiling points, and ability to conduct electricity when dissolved in water.
Covalent Bonds: Types and Examples
Pure Covalent Bonds
- A pure covalent bond forms when two atoms share electrons equally; for instance, two hydrogen atoms combine to form H₂ by sharing their single electrons.
Polar Covalent Bonds
- In polar covalent bonds like sulfur monoxide (SO), atoms share electrons unequally due to differences in electronegativity; each atom ends up with a partial charge.
Coordinated Covalent Bonds
- Coordinated covalent bonds involve sharing multiple pairs of electrons; ammonia (NH₃), where nitrogen shares three pairs with hydrogen atoms to achieve stability.
Hydrogen Bonds
- Hydrogen bonds are significant in water molecules where oxygen shares its six outer-level electrons with two hydrogen atoms. This allows extensive bonding among water molecules.
Properties of Metals
Common Metal Properties
- Metals exhibit malleability, ductility, luster, and conductivity. They can change shape without breaking while reflecting light effectively.
Conductivity Explained
- Metals conduct electricity because their outermost electrons are loosely bound. When metal atoms come close together, these free-moving conduction electrons allow for efficient electrical flow.
Understanding Electrical Conductivity in Metals
The Nature of Metals as Conductors
- All metals are electrical conductors due to their structure, which can be likened to a giant molecule where electrons are shared equally among all atoms.
- Metals can be represented as structures of positively charged ions held together by a fluid of mobile electrons.
Interaction with Electric Charges
- When a positive charge is placed near a metal, it attracts the negatively charged mobile electrons towards itself, causing them to accumulate on the nearest surface.
- This accumulation results in an imbalance, creating net positive ions on the farther surface that are not countered by electrons.