CHEM 1101 Chapter Notes - Chapter 3: Ionic Compound, Alkali Metal, Electron Affinity
Ions
• General Rule: metals like to form compounds with nonmetals
• Ion- gaining or losing 1+ electrons→ The atom becomes charged
o Cation- loss of 1+ electron (+)
▪ Ex: Na+
o Anion- gain of 1+ electron (-)
▪ Ex: Cl-
Periodic Properties
• Ionization Energy- energy required to remove 1 electron from a single atom in gaseous
state
• Electron Affinity- energy released on adding an electron to a single atom in the gaseous
state
o Alkali metals
▪ Small ionization energy- electrons easily lost
▪ Small electron affinity- electrons not easily gained
▪ Net Result: cation formation favored
o Halogen
▪ Large ionization energy- electron not easily lost
▪ Large electron affinity- electron easily gained
▪ Net Result: anion formation favored
o Main group elements neither lose nor gain electrons easily
• Cations and anions form neutral bonds
Ionic Bonds
• Ionic Bonds- electrical attractions between ions of opposite charges in a crystal
• Ionic Solid- crystalline solid held together by ionic bonds
• Ionic Compound- compounds that contain ionic bonds
Some Properties of Ionic Compounds
• Ions vary in size and charge
• Ions in ionic solids held together by attraction to neighbors
o Dissolving in water frees them if attraction to water is more power
• Ions need to gain large amounts of energy by being heated to loosen their grip
• Ionic solids will shatter if struck sharply
Ions and the Octet Rule
• Main group elements undergo reactions leaving them with 8 valence electrons
• Main group metals tend to lose e- to gain octet
• Reactive main group nonmetals tend to gain e- to attain octet
o Product ions have filled s and p shells
Naming Ions
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Document Summary
Ions: general rule: metals like to form compounds with nonmetals. Ion- gaining or losing 1+ electrons the atom becomes charged: cation- loss of 1+ electron (+, ex: na, anion- gain of 1+ electron (-, ex: cl- Ionic bonds- electrical attractions between ions of opposite charges in a crystal. Ionic solid- crystalline solid held together by ionic bonds. Ions in ionic solids held together by attraction to neighbors: dissolving in water frees them if attraction to water is more power. Ions need to gain large amounts of energy by being heated to loosen their grip. Naming ions: metal cations (1a-3a) (cid:373)etal + (cid:862)io(cid:374)(cid:863, ex: potassium ion, transition metals, old system , smaller charges= -ous, ex: chromus ion, larger charges= -ic, ex: chromic ion, new system (roman numeral, ex: cr 2+ chromium (ii) Cr 3+ chromium (iii: anions -ide + (cid:862)io(cid:374)(cid:863, ex: sulfide ion. Formulas of ionic compounds: chemical formula tells ratios of atom to cation (equal charge)