Sci10 UA Ion Formation

Introduction to Ion Formation

• Ion Formation: Changing from a neutral atom to a charged ion by gaining or losing electrons.

• Neutral Atom: Equal number of protons and electrons; possesses no charge.

The Octet Rule

• Definition: Atoms bond to achieve eight electrons in their valence shell for stability.

• Exceptions: Hydrogen, lithium, and beryllium, which aim for two electrons (similar to helium).

Ionization Process

• Ionization: The process where atoms gain or lose electrons to form ions.

• Valence Electrons: Electrons in the outermost shell that determine bonding behavior.

• Gaining Electrons: Results in a negative charge, forming anions (e.g., Chlorine becoming Cl-).

• Losing Electrons: Results in a positive charge, forming cations (e.g., Sodium becoming Na+).

Examples of Ion Formation

• Chlorine (Cl):

  • Has 7 valence electrons, gains 1 electron to achieve full shell.

  • Becomes chloride ion (Cl-), commonly forms a -1 charge.

• Sodium (Na):

  • Has 1 valence electron, loses 1 electron to achieve stability.

  • Becomes sodium ion (Na+), commonly forms a +1 charge.

Cations and Anions

• Cations: Positively charged ions from losing electrons; typical of metals (e.g., Mg2+, Ag+, K+).

• Anions: Negatively charged ions from gaining electrons; typical of non-metals (e.g., O2-, S2-).

• Memory Tricks:

  • Cation: "Cats have paws" (positive).

  • Anion: "Onion" makes you cry (negative).

Stability and Reactivity

• Ions are often more stable than neutral atoms because they achieve a full valence shell.

• Reactive Atoms: Alkali metals (e.g., Na) and halogens (e.g., Cl) are highly reactive due to their valence electrons.

Recording Ion Charges

• Superscripts: Indicate the charge after the element symbol (e.g., Na+).

• Periodic Table: Charges can often be found; otherwise, calculate based on proximity to the nearest noble gas.

Step-by-Step Calculation Example

• Sodium (Na):

  • Closest noble gas: Neon (Ne).

  • Sodium has 11 protons/electrons; needs to lose 1 electron to match Ne, resulting in Na+.

Bohr Model and Electron Orbital Diagram

• Bohr Model: Visual representation showing 2 electrons in the first shell and 8 in the second for Na+.

• Electron Orbital Diagram: Similar but simpler; shows electron distribution without detailed drawing.

Naming Ions

• Naming Monatomic Ions:

  • For metals: Use the same name + "ion" (e.g., Sodium -> Sodium ion).

  • For non-metals: Change ending to "ide" (e.g., Chlorine -> Chloride).

  • Examples:

    • Iron -> Iron ion

    • Bromine -> Bromide

Summary of Charges from Groups

• Group 1: +1 charge (alkali metals).

• Group 2: +2 charge (alkaline earth metals).

• Group 15: -3 charge.

• Group 16: -2 charge.

• Group 17: -1 charge.

• Group 18: No charge (noble gases).

• Notable Exceptions: Transition metals may have variable charges.

Practice and Application

• Exercises: Pages 8, 9, and 10 in chemistry booklet to reinforce concepts.

• Calculation Examples: Determine protons, neutrons, and electrons for given ions.