Basic Structure of Atoms
Atoms consist of protons, neutrons, and electrons.
Protons:
Positively charged particles (+).
Each proton has an atomic mass of 1.
Neutrons:
Neutral particles with an atomic mass of 1.
Electrons:
Negatively charged particles (–) found outside the nucleus.
Valence Shell:
The outermost shell of an atom where electrons reside.
Atoms strive for a full valence shell for stability.
Electron Sharing:
Atoms can share, give away, or receive electrons to achieve a full valence shell.
Complete valence shells lead to chemical bonding.
Types of Chemical Bonds:
Covalent Bonds:
Involve the sharing of electrons between atoms.
Can be nonpolar (equal sharing) or polar (unequal sharing).
Ionic Bonds:
Form when one atom transfers electrons to another, creating charged ions (cations and anions).
The attraction between positive and negative ions results in an ionic bond.
Electronegativity:
Measure of an atom's ability to attract electrons.
In water (H2O): oxygen is more electronegative than hydrogen, leading to polar covalent bonds.
Resulting Charges:
Oxygen: slightly negative.
Hydrogen: slightly positive.
Hydrogen Bonds:
Weak attractions between the partially positive hydrogen atoms and the partially negative oxygen of other water molecules.
These bonds are constantly forming and breaking, contributing to water's unique properties.
Cohesion:
Water molecules are attracted to each other, leading to surface tension.
Example: Insects walking on water are supported by surface tension.
Adhesion:
Water molecules cling to other substances.
Important for processes like water movement up plant roots.
Density:
Ice is less dense than water, allowing it to float. This phenomenon helps aquatic life survive in cold climates.
Heat of Vaporization:
Significant energy is required for water to change from liquid to vapor, contributing to temperature regulation in environments.
Solvent Properties:
Water is a universal solvent, facilitating chemical reactions and transporting nutrients.
Covalent Bonds: Strongest; sharing electrons.
Ionic Bonds: Formed through the transfer of electrons; strong attraction between charged ions.
Hydrogen Bonds: Weak, easily broken, important for the structure of water and other biological molecules.