Types of Bond

• • All matter is made of atoms.​
  • Atoms are very small, having a radius of about 1 × 10-10 meters.  The basic structure of an atom is a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.​
  • The radius of a nucleus is less than 1/10000 of the radius of an atom. Most of the mass of an atom is concentrated in the nucleus. (Most of the atom is empty space)
• An ion is a charged particle. This charge can be positive or negative. An atom has no charge as it has an equal number of positive protons and negative electrons​

  ​

  Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable. 
• An atom that loses electrons has more protons than electrons and so has a positive overall charge. This is called a positive ion.
• An atom that gains electrons has more electrons than protons and so has a negative overall charge. This is called a negative ion.
• Atoms form ions because they want a full shell of electrons. Atoms achieve this full shell in three different ways. These different ways are the different chemical bonds.​

  There are two types of atoms found in the periodic table. Metals and non-metals
• Metals and non-metals transfer electrons and the atoms become charged. These are called ions. Metal ions are positively charged and non-metal ions are negatively charged. The positive ions and the negative ions are attracted to each other and bond together by electrostatic attraction. This is known as ionic bonding.
• Non-metals can share electrons between atoms. This type of bonding is known as covalent bonding. Atoms held together by covalent bonds are called molecules.
• Metals form positive ions which are attracted to the negatively charged delocalised (free to move) electrons that surround them. This is called metallic bonding.
• There are 3 types of bonding: covalent, ionic, and metallic.
• When a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions. 
• Ionic bonds are formed between a metal and non-metal.
• The ionic bond is the electrostatic force of attraction between the positively charged metal ion and the  negatively charged non-metal ion.
• The further away an electron is from the nucleus, the easier it can be lost in reactions. Because there is a weaker attraction holding the electron to the nucleus. This makes the atom more reactive.
• An ionic compound is a giant structure of ions. The ions have a regular, repeating arrangement called an ionic lattice. The lattice is formed because there is an electrostatic attraction between ions and they form a regular pattern with oppositely charged ions next to each other. 
• (COMPOUND) is a giant ionic lattice made of positive (METAL) ions and negative (NON-METAL) ions. (1 mark)​

  Because these ions are oppositely charged they are held together by the electrostatic force of attraction. (1 mark) ​

  Because this force acts in all directions, you can form a giant lattice of alternating positive and negative ions. (2 marks. 1 for lattice and 1 for positive and negative ions)​
• An ionic formula is effectively an empirical formula. Empirical formulae show the simplest ratio of elements in a compound. An ionic formula is the simplest ratio of ions in a formula.
• A covalent bond forms when two non-metal atoms share a pair of electrons.  ​

  ​

  Covalent bonds are strong - a lot of energy is needed to break them. Substances with covalent bonds often form molecules with low melting and boiling points, such as hydrogen and water.
• A molecule is a particle made up of two or more atoms that are chemically bonded together by covalent bonds.
• Metals want to lose their electrons to form a full outer shell. The electrons in the outer shell become delocalised, which means they are free to move leaving a positive ion behind. The positive ions are then attracted to the delocalised electrons by the electrostatic force of attraction. 
• The sharing of delocalised electrons gives rise to strong metallic bonds. ​

  The delocalised electrons can move and conduct electricity and heat through the metal.​

  Metal ions form a large lattice structure held together by the electrostatic attraction of the positive ion and the delocalized electrons
• Lattice:- 3 dimensional regular arrangement of atoms​

  Positively charged ions:- metal atoms that have lost electrons​

  Delocalised electrons :- electrons that are not fixed to one atom​

  Electrostatic attraction :- force between opposite charges
• Metals are good conductors as the delocalised electrons are free to move.​

  Metallic bonds are very strong and are difficult to break.