bonding & structure

• An atom can bond with other atoms in order to achieve a stable electron arrangement.
• A stable electron arrangement is when an atom has a full outer shell of electrons. Atoms achieve this electron arrangement by either gaining, losing or sharing electrons.
• There are 3 different types of bonding:

  1. Covalent Bonding

  2. Ionic Bonding

  3. Metallic Bonding
• A covalent bond forms when two positive nuclei are held together by their common attraction for a shared pair of electrons.
• Smaller covalent structures can have four distinct shapes: linear, angular, triagonal pyramidal, and tetrahedral.
• A molecule will have a linear shape when it has two atoms bonded to each other, which can either be the same or different, for example, hydrogen bromide, HF.
• A molecule will have an angular shape when it has one atom bonded to two other atoms, for example, water, H 2 O.
• A molecule will have a trigonal pyramidal shape when it has one atom bonded to three other atoms, for example, ammonia, NH 3.
• A molecule will have a tetrahedral shape when it has one atom bonded to four other molecules.
• Their is 2 types of covalent bonding;

  covalent molecular

  covalent network
• Covalent molecular substances have strong covalent bonds within the molecule but weak attraction between the molecules.

  This means these substance have low melting and boiling points and are usually liquid or gas at room temperature.
• Covalent network substances have strong covalent bonds within the molecule and strong attractions between the molecules.

  This means these substances have high melting and boiling points and are usually solid at room temperature.

  Covalent network structures don’t form simple structures but have large complex structures with hundreds of atoms.
• Covalent substances do not conduct electricity, regardless of state.

  This is due to the fact that electrons within the structure are not free to move to allow electricity to pass.
• Ionic bonding occurs when two atoms gain and lose electrons simultaneously to each other. The resulting products gives two ions – a positive and a negative ion.
• Ionic bonds are the electrostatic attraction between positive and negative ions.
• An ionic bond is generally strong and ionic substances have high melting and boiling points. They are usually solids at room temperature.

  Ionic compounds form complex lattice structures of

  oppositely charged ions.
• Ionic substances only conduct electricity when liquid, in solution or molten this is because then the electrons are free to move
• there are 7 diatomic elements - these are elements that are found joined together by covalent bonds
• covalent substances are made up of non-metal atoms which share pairs of electrons to make stable outer shells
• covalent bonds occur when non-metals share pairs of electrons
• ionic bonding occurs between metal and non metal atoms, where the metal atom loses electrons to form a positively charged ion
• there are 7 diatomic elements - these include hydrogen (H2), nitrogen (N2) , oxygen (O2), fluorine (F2), chlorine (Cl2), bromine (Br2) and iodine (I2)