Ions and Ionic Bonds

Study Notes

Atoms can gain or lose electrons to form ions, which are charged particles, to achieve a more stable state.
Ions come in two types: cations (positive ions) formed by losing electrons and anions (negative ions) formed by gaining electrons.
Cations are named as they are, while anions are named using the ending "-ide" (e.g., chloride).
Electron transfer occurs when one atom loses an electron and another atom gains it.

Sodium (Na) tends to lose its one electron to form Na+, as it's energetically favorable to donate one electron than to find seven more to fill its outer shell.
Chlorine (Cl) tends to gain one electron to form Cl-, as it's easier to gain one electron than to lose seven to fill its outer shell.
Sodium transfers one electron to chlorine, resulting in the formation of Na+ and Cl- ions, which satisfy the octet rule.

Ionic bonds are formed between ions with opposite charges, such as positively charged sodium ions and negatively charged chloride ions.
The attraction between oppositely charged ions results in the formation of compounds like sodium chloride (table salt).
Ionic compounds, like table salt, consist of many ions arranged in a repeating, predictable 3D pattern (a crystal).
Electrolytes, including sodium, potassium, and calcium, are necessary for nerve impulse conduction, muscle contractions, and water balance.

Atoms can also become more stable by sharing electrons, forming covalent bonds.
Covalent bonds are more common than ionic bonds in the molecules of living organisms.
Covalent bonds can be single, double, or triple, depending on the number of electron pairs shared between atoms.
The more electrons shared between two atoms, the stronger their bond will be.
Covalent bonds are key to the structure of carbon-based organic molecules like DNA and proteins, as well as smaller inorganic molecules like H2O, CO2, and O2.

A single water molecule (H2O) consists of two hydrogen atoms bonded to one oxygen atom.
Each hydrogen atom shares an electron with oxygen, and oxygen shares one of its electrons with each hydrogen.
The shared electrons split their time between the valence shells of the hydrogen and oxygen atoms, giving each atom a stable configuration.