Structure and bonding in applications of science

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  • Structure and bonding in applications in science.
    • The electronic structure of atoms.
      • The nucleus contains the protons and neutrons. The electron orbit the nucleus in shells.
      • Relative charge - Proton = +1 Neutron = 0  Electron = -1
        • Relative mass - proton = 1     neutron = 1    electron = Very small (1/1840)
      • Atoms are neutral (they have no overall charge)
        • Therefore the number of protons = the number of electrons.
      • Atomic number = number of protons in the nucleus of an atom.              Mass number = protons + neutrons
      • Number of protons = the atomic number of the atom.
      • Number of electrons= same as the number of protons in the atom (not an ion).
      • Number of neutrons = mass number - atomic number
    • Group number = electrons in the outer shell                  Period number = number of shells
    • Electronic structure and orbitals.
      • A shell is also known as an energy level.
        • Shells contain subshells which contain orbitals.
          • An orbital is a region of space where an electron is likely to be found and each orbital holds 2 electrons.
          • The size of the shell determines how many subshells it can contain.
          • An s subshell has 1 orbital and can therefore hold 2 electrons.     A p subshell has 3 orbitals and can therefore hold 6 electrons.     A d subshell has 5 orbitals and can therefore hold 10 electrons.
    • Bohr theory
      • Electrons exist in fixed energy levels.
        • An electron can exist in the 1st energy level or the 2nd energy level but it cannot exist somewhere in between.
          • An electron can move to a higher energy level by absorbing radiation.
            • An electron can fall to a lower level emitting radiation.
    • Ionic bonding
      • Ionic bonding occurs between a metal and a non-metal.
      • When the atoms react the metal atom loses electrons and the non-metal atom gains electrons. The atoms then become ions.
        • An ion is something that has gained or lost an electron. Positive ions have lost electrons.
      • The result of the electrostatic attraction between a positive and negative ion.
      • Structure= a giant ionic lattice in which many ions are held together by strong electrostatic attractions.
      • Ionic compounds have high melting and boiling points because of the giant lattice structures and there is a strong electrostatic attraction between the positive and negative ions.
      • Ionic compounds don't conduct electricity when solid because ions cannot move.
      • Ionic compounds conduct electricity when melted or in solution because the ions are free to move.
    • The strength of the ionic bond is down to the attraction between the positive and negative ion. The bigger the attraction the greater the strength of the ionic bond.
    • The more shells an ion has the bigger the ion will be.
      • The size of the ion increases as you go down a group.
    • The more protons in the nucleus the smaller the ion.
      • The size of the ion decreases as there are more protons in the nucleus.
    • Covalent bonding
      • A covalent bond is formed between two non-metals.
      • There is a strong electrostatic attraction between the two nuclei and the shared pair of electrons.
      • Dative covalent
        • Formed when both electrons in the shared electron pair come from one atom.
        • Atoms that donate:     group 5,6,7      Atoms that Accept: H+ and group 3.
      • Single covalent bonds
        • 1 electron pair is shared.Weakest and longest type of bond.
      • Double covalent bond
        • 2 electron pairs are shared.
      • Triple covalent bond
        • 3 electron pairs are shared. strongest and shortest type of bond.

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