ATOMIC STRUCTURE AND PERIODIC TABLE ?

ATOMIC STRUCTURE AND PERIODIC TABLE ?

1. ATOMIC THEORIES

   • 1808 - John Dalton
     • All matter consisted of tiny particles called atoms
     • Atoms could not be divided into smaller particles
     • Atoms of the same element were alike
     • Atoms combined in simple whole number ratios
     • The first atomic model
   • 1897 - J. J. Thomson
     • Atom contained negatively charged particles called electrons
     • Atoms were positively charged spheres with negatively charged electrons embedded in them
   • 1911 - Lord Rutherford
     • Atom consisted of empty space with a dense nucleus containing positively charged protons in the centre.
     • Negatively charged electrons orbited the nucleus
     • Orbiting electrons would eventually lose energy and spiral in towards the nucleus.
   • 1913 - Niels Bohr
     • Electrons orbit the nucleus at different energy levels
     • Only electrons with specific amounts of energy could exist at each level.
   • 400 BC - Democritus
     • All substances consisted of tiny indestructible particles called atoms.

2. PERIODIC TABLE

   • There are many different types of atoms, each with its own
     • Name
     • Atomic mass
       • It is the sum of the number of protons and neutrons in the atom.
     • Atomic number
       • It is the number of protons found in the nucleus of an atom
     • They are called chemical elements.
       • Which are organized on the periodic table in the order of their atomic number
   • Structure - The elements are arranged into
     • Groups
       • It is a column of elements down the table
         • Elements in a group have electrons arranged in similar ways
           • So they have similar chemical physical and chemical reactions and properties.
       • Group 1 - Alkali Metals
         • The alkali metals all react strongly with water to form basic solutions
       • Group 2 - Alkaline earth metals.
       • Groups 3 to 12 - Transition metal
       • Group 17 - Halogens
         • The halogens are brightly coloured elements.
       • Group 18 - Noble gases
         • The noble gases are inert and do not readily react with other substances
       • Types
     • Periods
       • It is a row of elements across the table
         • Elements in a period have consecutive atomic numbers.

3. COMPOUNDS

   • Ionic Compounds
     • An ion is an atom that has gained or lost one or more electrons.
     • Ionic Bonds are formed when stoms ‘lose’ or ‘gain’ electrons
       • So that their outer shells become ‘filled’ if they are not already full
     • Ions can be
       • Negative
         • Are atoms that have gained electrons and have more electrons
       • Positive
         • Are atoms that have lost electrons and have more protons
     • Depending on which is the easier way to have a full outer shell.
   • Covalent compounds
     • It is the result of non-metal atoms effectively ‘stealing’ electrons from metal atoms.
     • Atoms can also achieve stable electronic configurations by sharing electrons with other atoms to gain a full outer shell.
     • It is also possible to draw a structural formula that determines the chemical formula of the compound.
       • It also determines the chemical formula of the compound.
     • They are usually insoluble in water.
       • Soluble
         • Dissolves in a solid, liquid or gaseous solvent.
       • Insoluble
         • Doesn't dissolves
   • Compounds
     • Made from atoms of differing elements bonded to each other
   • Chemical Bond
     • When the outer shell electrons of atoms interact, atoms can become chemically joined together to form molecules.
       • The shared of electrons are called bonding electrons

4. ATOMS

   • It is the basic unit of matter
     • It is the smallest thing that can have a chemical property.
       • Atoms consist of a central nucleus of positive electrical charge (Protons and Neutrons) surrounded by an electron shell of negatively charged
         • When atoms are excited they emit light that can be observed as a series of colored lines with dark spaces in between, called lime spectrum

5. ATOMIC STRUCTURES

   • Quarks
     • It is an elementary particle and one of the two fundamental constituents of matter
       • They combine and form hadrons as the subatomics particles:
         • Neutrons
           • No electric charge and a mass slightly greater than that of a proton
             • The symbol is n or n 0
         • Protons
           • Mass defined as 1 and a charge of +1 (positive charge)
             • It is indicated by either the symbol p or p+
   • Eletrons
     • They are generally negative in charge
       • They and their mass are much smaller than the nucleus of the atom.
         • Electrons are constantly moving in their shells
           • Electrons play a major role in all chemical bonds

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