Metals

• Periodic Table of ElementsHemera Technologies/PhotoObjects.net/Getty Images
  
  Metals comprise the yellow, red, orange, and pink regions in the periodic table shown. Metals are elements on the periodic table that possess the following characteristics:
  
  - Lose outer electrons to form positive ions, such as Na+, Ca+2, Cu+2, Au+2
  
  - Form basic oxides and hydroxides
  
  - Malleable (easily hammered into shapes) and lustrous or shiny (the outer electrons reflecting light)
  
  - Generally ductile (can be stretched into wires) and conduct electricity well
  
  

Acidity

• Perchloric acidPhotoObjects.net/PhotoObjects.net/Getty Images
  
  According to Visionlearning.com, "Acids taste sour, are corrosive to metals, change litmus (a dye extracted from lichens) red, and become less acidic when mixed with bases" The pH of an acidic solution is below 7 on a scale of 1 to 14; the stronger the acid the lower the pH. The common strong acids are sulfuric, hydrochloric, perchloric and nitric, and the common weak acids are acetic (vinegar) and oxalic. Perchloric acid is used in rocket fuel.
  
  

Beneficial Effects of Acidity on Metals

• Lead-acid battery -- lead in sulfuric acid.Ablestock.com/AbleStock.com/Getty Images
  
  Some of the beneficial ways to utilize the chemical reaction between acids and metals are:
  
  - Lead-acid batteries, which runs cars, boats and other transportation and provide back-up power for everything from computers to hospital emergency lighting
  
  - Jewellery industry applications
  
  - Clean metallic surfaces and coins
  
  - Clean gold dentures -- acetic acid or vinegar
  
  - Electropolish or etch aluminium, molybdenum and other metals -- perchloric acid; danger of detonation
  
  

Negative Effects of Acidity on Metals

• Making lead battery explosives at the Israeli borderWarrick Page/Getty Images News/Getty Images
  
  When acid comes in contact with metals hydrogen gas is released and a salt is formed. Metals with lower atomic numbers, such as sodium, magnesium and potassium, can react vigorously with acids. Terrorists and compatants can take advantage of this reaction to make explosives.