Chapter 2 form 4
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Chapter 2 form 4



Chemistry chapter 2 form 4

Chemistry chapter 2 form 4
The structure of the Atom



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Chapter 2 form 4 Chapter 2 form 4 Presentation Transcript

  • Particulate Nature of Matter
    • Matter- anything that has mass and occupies space
    • Particle + particle = matter
    Iron (Fe) from iron atom NaCl from sodium ions and chloride ion H2O from water molecules
    • Atoms
    • an atom is the smallest particle of an element
    • example : “O” for oxygen atom
    • Molecules
    • contains two or more atoms which are bonded together ( maybe same element or not )
    • example : H2 and CCl4
    • Ions
    • -ions are charged either positive or negative
    • -are form in liquid or molten state
    • -lose electron (+ ion),gain electron (- ion)
    • example : Na + , Mg 2+ , Br -
  • Kinetic Theory of Matter
    • Solids
    • - strong forces of attraction
    • - particle only vibrate (fixed shape and volume)
    • Liquids
    • - force of attraction weak than solid
    • - particle can move around (follow container shape)
    • Gases
    • - no attraction between particles
    • - particle move faster and freely (zigzag)
    • Diffusion
    • - example : perfume
    • - light and small particle diffuse faster
    • - heavy and large particle diffuse slow
  • The Atomic Structure
    • Democritus
    • Democritus proposed that if a piece of gold cut into smaller until cannot cut anymore, called atom.
    • John Dalton (1766-1844)
    • J.J.Thomson (1856-1940)
    • Ernest Rutherford (1871-1937)
    • Neils Bohr (1885-1962)
    • James Chadwick (1891-1974)
  • John Dalton(1766-1844)
    • In 1808, he proposed :
    • All matter is composed of atoms.
    • Atoms cannot be created or destroyed.
    • All the atoms of an element are identical.
    • The atoms of different elements are different.
    • When chemical reactions take place, atoms of different elements join together to form compounds.
  • J.J.Thomson (1856-1940)
    • It was the first model of the atom.
    • 1897- Thomson discovered the electron (negatively- charged).
    • Thomson suggested that an atom is a positively- charged sphere with electrons embedded in it like a raisin pudding.
  • Ernest Rutherford (1871-1937)
    • 1914- Rutherford discovered the proton
    • Rutherford model was based on the alpha particle scattering experiment
    • He proposed
    • 1) all the positive charge of an atom is concentrated in the nucleus
    • 2) an atom consists of a positively-charged nucleus with a cloud of electrons surrounding the nucleus
  • Neils Bohr (1885-1962)
    • He was a student of Rutherford
    • He proposed
    • 1) electrons are arranged in orbits (electron shells) around the nucleus of the atom
    • 2) electrons in a particular path have a fixed energy.
    • To move from one orbit to another, an electron
    • must gain or lose the right amount
    • of energy
  • James Chadwick (1891-1974)
    • He proposed that the nucleus of the atom contains proton and neutron and the nucleus is surrounded by a cloud of electrons
  • Proton number and nucleon number
    • Proton number = the number of protons in an atom
    • Also known atomic number
    • No two different element have same proton number
    • Atom are neutral. Proton number also tells us number of electron.
    • Nucleon number also known mass number
    • Nucleon no. = proton no. + neutron number
    • How nucleon no. and proton no. of an element is written ?
  • Symbol of elements
    • Most symbols are taken from the English name
    H C N B Element Symbol Hydrogen Carbon Nitrogen Boron
    • Some symbol are made up of two letters
    • Some symbols are based on the Latin or Greek name
    Zinc Zn Aluminium Al Calcium Ca silicon Si Silver Ag Copper Cu Iron Fe Gold Au
  • Isotopes and their importance
    • Are atoms of the same element with the same proton no. but different nucleon no. or neutron no.
    • Isotopes of an element have same chemical properties but different physical properties
    • Example of isotopes
    • Some isotopes are stable while the rest unstable ( radioactive isotopes)
  • Uses of isotopes
    • Medicine
    • Cobalt-60 is a radioactive isotope of cobalt. It decays by giving out gamma radiation. In radiotherapy, maglinant cancer cells are killed by directing a beam of gamma rays towards cancer cells
    • Agriculture
    • radiation from radioisotopes is used to sterilise pests such as insects that destroy crops.
    • Industry
    • Gamma radiation is used to detect whether canned food or bottled drink is completely or partially filled
  • Electronic structure of an Atom
    • The electron in atom are arranged in shell around its nucleus
    • Electron start to fill up the shells from the inner shells
    • The first shell is the shell that nearest to nucleus and can hold just 2 electrons
    • Second shell can hold 8 electrons
    • Third shell can hold 8 electrons
    • All of this is called the electron arrangement or electronic configuration of the atom
    • Draw electronic arrangement if proton number is 4,5 and 6
  • Valence electrons
    • Outermost shell of an atom is called the valence shell
    • This shell should have electrons before it can be called a valence shell
    • The electrons in the valence shell are called the valence electrons
    • Elements with the same number of valence electrons have the same chemical properties
    • Lets see the example
    • susunan elektron.swf