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Classifying the Elements

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Metals and Non-Metal

Properties of Metals

• malleable
• ductile
• sonorous
• shiny
• conduct heat
• conduct electricity
• hard and strong

Non Metals

• brittle
• dull
• do not conduct electricity
• do not conduct heat
• not magnetic

Alkali Metals

• very reaction (have to be stored under oil to prevent reaction with air)
• form ions with 1+ charve.
• soft and can be cut with a knife
• potassium and sodium float on water

Trends down the group

• atomic size increases (increased no of electrons and shells)
• lose outer shell electron to form 1+ charged ions. Therefore reactivity increases as you go down the group. The electron is farther away from the nucleus.
• melting points decrease

Reactions:

• alkali metals with oxygen in the air
  • Sodium + Oxygen = Sodium Oxide
  • 4Na + O₂ -> 2NaO₂
• alkali metals with water
  • gives off hydrogen gas
  • resulting solution is alkali
  • Sodium + Water -> Sodium Hydroxide + Hydrogen
  • 2Na + 2H₂0 -> 2NaOH + H₂
• alkali metals with halogens
  • they react rapidly with halogens
  • Sodium + Chlorine -> Sodium chloride
  • 2Na + Cl₂ -> 2NaCl

Halogens

• non metals
• form ions with 1- charge
• very reactive
• toxic
• as you go down the group the colour of vapour becomes darker
  • fluorine - yellow
  • chlorine - green
  • bromine - red
  • iodine - violet
• Halogens are used as bleaching agents

Trends as you go down the group

• atomic size inicreases
• reactivity decreases (easier to gain electrons when electron shell is closer to the nucleus)
• melting and bioling point increase

Reactions

• halogens with hydrogen
  • Chlorine + Hydrogen -> hydrogen chloride (hydrochloric acid)
  • Cl₂ + H₂ -> 2HCl
• halogens with metals (forms a salt)
  • Magesium + Bromine -> Magnesium bromide
  •  2Mg + Br₂ -> 2MgBr

Displacement Reactions with Halogens

• A more reactive halogen will displace a less reactive one.
• Example: chlorine can displace bromine from potassium bromide, but cannot displace fluorine from potassium fluoride.
  • Cl₂ + 2KBr -> 2KCl + Br₂  (chlorine displaced bromine)
  • Br₂ + 2KI -> 2KBr + I₂ (bromine displaced iodine)
  • Br₂ + 2KF -> 2KF + Br₂ (bromine can't displace fluorine)

Noble Gasses

• gasses at room temperature
• uncreactive
• density with increase in atomic size
• Argon is used inside light bulbs
• Helium is used in hot air ballons
• boiling point increases as you go down the group

Transition Metals

• hard dense metals
• not very reactive
• often used as catalysts
• have variable valency (different charges,  Fe²⁺ Fe³⁺)

Some metals form oxides in reaction to oxygen

some metals form basic oxides

some non-metals form acidic oxides

About the Author

by: Admin
Total views: 1762
Word Count: 1229
Date: Sun, 21 May 2006 Time: 12:00 AM
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