Atomic Structure

Atomic Structure

1. The atom

   • Mostly made out of empty space
   • At centre of the atom is a tiny positive charge particle called the nucleus
   • Moving round the nucleus are even smaller particles called electrons
   • Electrons carry a negative charge
   • Atomic number and structure of the atom
     • atomic number = How many protons there are in an atom
     • Atomic number gives the following information
       • The size of the positive charge (Number of protons) in the nucleus.
       • The number of the negatively charged electrons orbiting the nucleus of an atom
       • If the atomic number is 6
         • 6 electrons orbit the nucleus
         • Nucleus has 6+ charge
         • Nucleus contains 6 protons
   • Summary: The atom is made from 3 smaller particles

2. The Neutron

   • In 1932, James Chadwick discovered that atoms contained a third particle called the neutron
   • The neutron is found in the nucleus of the atom and has zero charge
   • It is neutral
   • The neutron has the same mass as a proton

3. Proton

   • positive charge
   • Located in the nucleus

4. Neutron

   • neutral charge
   • located in the nucleus

5. Electron

   • Negative charge
   • located in the energy level

6. Though atoms are made up of charged particles they are neutral. The positive charge of the protons in the nucleus is cancelled OUT by the negatively charged electrons

7. Electrons

   • Energy Levels
     • Electrons fill up the lowest energy levels first
     • The first energy level can hold 2 electrons
     • The second energy level can hold 8 electrons
     • The third energy level can hold 8 electrons
   • Electron Arrangement
     • How the electrons fill up the energy levels in an atom is called the electrical arrangement
     • Silicon : Si
       • Atomic no. = 14
       • Electron arrangement = 2,8,4
     • Can be found in Data booklet pg6

8. the number of outer electrons relate to the group number as it is the same

9. Number of outer electrons relate to the reactivity as it increases so does the reactivity

10. Atomic and mass numbers

    • Atoms are made of 3 smaller particles. these particles are called the sub-atomic particles as they are smaller than the atom
    • The proton and neutron have the same mass of 1 amu
      • electron has the mass of zero
    • Mass of an atom comes from the proton and neutron in the nucleus of the atom
    • Mass number = the total number of protons and neutrons in the nucleus
    • Knowing the atomic no. and the mass no. of an atom, the no. of neutrons in the nucleus can be calculated.
      • Neutron no. = Mass no. - atomic no.

11. Isotopes

    • Two or more forms of protons but have different no. of neutrons
    • All elements have two or more isotopes

12. Periodic Table and ions

    • The periods relate to the filing of the energy levels with electrons
    • The rows in the periodic table are called periods

13. Atoms Joining

    • Atoms use their outer electrons to join. It is the outer electrons on an atom which gives the atom its chemical properties
      • One way atoms can join is to TRANSFER one or more electron(s) from one atom to another
        • When an electron transfers from one atom to another the atoms will no longer be electrically neutral
          • Charged atoms are called ions
            • Atoms have equal numbers of positive charges ( protons ) in the nucleus and negative electrons.
              • Atoms are neutral.
                • When an atom loses an electron it becomes a positively charged ion
                  • Opposite electrical charges attract
                • When an atom gains an electron it becomes a negatively charged ion

14. IOn Symbols

    • Li = Li+ + e-
      • Lithium ion has 1 positive charge. Its atom lost 1 electron
      • 2,1 changed to 2
    • O + 2e- = O2-
      • Oxide ion has a 2- negative charge. The oxygen atom gained 2 electrons.
      • 2,6 changed to 2,8
    • Al + 3e+ = Al3+
      • Aluminium ion has a 3+ positive charge. Its atom lost 3 electrons
      • 2,8,3 changed to 2,8