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Atomicstructure 100524040127-phpapp01 (3)
 

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    Atomicstructure 100524040127-phpapp01 (3) Atomicstructure 100524040127-phpapp01 (3) Presentation Transcript

    • ATOMIC STRUCTURE
    • DEVELOPMENT OF ATOMIC MODELScientist Atomic Atomic Model Structure 1808- suggested that matter is made of tiny particles which are indivisible and indestructibleJohn Dalton An atom is like a miniature(1766-1844) billiard ball 1897- put forward the “plum pudding” model of the atom. The atom is like a sphere with small electrons Plum Pudding Model embedded in aJ.J Thompson positively charged -discovery of electron(1856-1940) mass
    • Scientist Atomic Atomic Model Structure 1911- shows that:  atom is spherical & - has a centre or - nucleus with a dense - positive chargeErnest Protons are the -Rutherford - positively charged(1871-1937) particles in the nucleus A system of electrons rotates Rutherford’s Solar around the nucleus System Model much like the planets orbiting around the sun
    • Scientist Atomic Atomic Model Structure 1913- showed that: Electrons orbit in specific energy levels called shells Each shell is capableNiels Bohr Bohr’s electrons orbiting in of holding a certain(1885-1962) number of electrons. shells 1932- discovered that: A particle in the nucleus which has no electric charge and called it neutronJames All nuclei (exceptChadwick hydrogen) contain(1891-1974) neutrons as well as protons
    • SUBATOMIC PARTICLES electron { proton nucleon + shell neutron + Atomic structure of an atom Atoms are made of three different types of subatomic particles called protons, neutrons and electrons Protons and neutrons are found in the nucleus and they are known as nucleons Nucleus is positively charged because the protons are positively charged and the neutrons are electrically neutral Electrons rotate around the nucleus in a certain orbit called shells, just like planets rotate around the sun
    • THE PROPERTIES OF SUBATOMIC PARTICLESSubatomic Proton Neutron Electron particlesSymbol p n e¯Relative +1 0 -1electricchargeRelative 1 1 _1__mass 1840 An atom is neutral when it has the same number of protons and electrons
    • PROTON NUMBER The number of protons in an atom of an element Proton number = number of protons
    • NUCLEON NUMBER The sum of protons and neutrons in an atom elementNucleon number = number of protons + number of neutrons
    • NUMBER OF NEUTRONS the difference between the nucleon number and the proton number Number of neutrons = nucleon number – proton number A neutral atom has the same number of protons and the number of electrons Different elements have different numbers of protons
    •  The number of protons, electrons and neutrons in a particular atom are given in the Periodic Table by the nucleon number and proton number A X Z A : proton number Z :nucleon number X: symbol of an element The number of protons, electrons and neutrons can be determined from the nucleon number and proton number
    • Example: (a) Sulphur 32 S 16 the symbol of the element above shows that it is sulphur Nucleon number = 32 Proton number = 16 Number of neutron = 32-16 = 16 So, sulphur atom has 16 protons, 16 electrons and 16 neutrons
    • Example: (b) Aluminium 27 Al 13 The symbol of the element above shows that it is aluminium Nucleon number = 27 Proton number = 13 Number of neutron = 27 – 13= 14 Aluminium atom has 13 protons, 13 electrons and 14 neutrons
    • Example: (c) Sodium 23 Na 11Number of protons = 11Number of neutrons = 23 - 11 = 12So, number of electrons = 11
    • Exercises1. What is matter?2. What are atoms, molecules and ions?3. How does the state of matter change with the change in temperature?4. How does the kinetic theory of matter explain the inter- conversion of the state of matter?5. How was the atomic model developed?6. What are the main subatomic particles of an atom?7. What is proton number?8. What is nucleon number?