chem sec 4

• Periodic table

  • It is arranged in order of increasing proton number
  • PERIOD- NUMBER OF SHELLS in an atom
  • GROUP- NUMBER OF VALENCE ELECTRONS
• FLOURINE - group 17 ( 7 valence electrons )

  CLOURINE - group 17 VALENCE ELECTRONS
• ISOTOPES - SAME PROTON , DIFFERENT NEUTRONS
• PERIOD ( SHELLS )

  • Li (2,1)
  • Be(2,2)
  • B(2,3)

  3 shells

  • Na (2,8,1)
  • Mg (2,8,2)
  • Al (2,8,3)
• when GOING DOWN GROUP, there is an INCREASE IN METALLIC PROPERTIES and DECREASE IN NON-METALLIC PROPERTIES
• how are elements organised ?

  • increasing proton number
  • no of valence electrons (GROUP)
  • no of electron shell (PERIOD)
  • metallic to non-metallic

  metal - element that GAIN valence electrons
• GROUP 1 ELEMENTS - ALKALI METALS

  • it is soft and can be easily cut
  • LOW MELTING AND BOILING POINT
  • LOW DENSITIES - Li , Na , K float
  • HIGHLY REACTIVE
• Li

  Na

  K

  Rb

  Cs

  Fr

  DOWN THE GROUP

  1. REACTIVITY INCREASES
  2. MELTING POINT DECREASES
  3. DENSITIES INCREASE
• ALKALI METALS ARE EXTREMELY REACTIVE

  ALKALI METAL + WATER — SOLUBLE BASE (ALKALI)
• LITHIUM - reacts QUICKLY , floats on water

  SODIUM- reacts VIOLENTLY , darts around the water , Reaction may be EXPLOSIVE

  POTASSIUM - reacts VERY VIOLENTLY , reaction is EXPLOSIVE
• SIZE OF ATOMS INCREASES

  • VALENCE ELECTRONS IS LOST MORE QUICKLY
  • REACTIVITY INCREASES
  • REDUCING TENDENCY TO GIVE ELECTRONS INCREASES
• GROUP 17 - HALOGENS

  • NON - METALS
  • exist as DIATOMIC MOLECULES
  • LOW MELTING AND BOILING POINT
• F

  Cl

  Br

  l

  At

  Ts

  - REACTIVITY DECREASES
• FLOURINE - PALE YELLOW

  CHLORINE- GREENISH YELLOW

  BROMINE- REDDISH BROWN

  IODINE - BLACK
• down the group

  • COLOUR INTENSITIES INCREASES ( GET MORE DARK )
  • MELTING AND BOILING POINT INCREASES
  • REACTIVITY DECREASES
• 2NaBr + Cl2 —— NaCL + Br2

  • from colourless solution to reddish - brown
• Fluorine chlorine bromine iodine

  most reactive ————————-least reactive
• DISPLACEMENT REACTION is when ONE ELEMENT TAKES THE PLACE OF ANOTHER ELEMENT in the compound
• GROUP 18 - NOBLE GASES

  • monatomic non - metals
  • COLOURLESS GAS at 25 degree
  • LOW MELTING AND BOILING POINT
  • INSOLUBLE IN WATER
  • UNREACTIVE