# Ionic Bonding

##### 1.21 Explain how ionic bonds are formed by the transfer of electrons between atoms to produce cations and anions, including the use of dot and cross diagrams
• Metal + Non-metal: 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
• NB: Ions – Atoms that have lost or gained electron/electrons.
• Electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram (see eg for NaCl below)

##### 1.22 Recall that an ion is an atom or group of atoms with a positive or negative charge
• Since an ion is formed from a metal losing an electron, i.e. becoming a positive metal ion or from a non-metal gaining an electron, i.e. becoming a negative ion…an ion is an atom or group of atoms with a positive or negative charge
• Cation = positive ion (+ -> ca+ion)
• Anion = negative ion (Negative -> aNion)
##### 1.23 Calculate the numbers of protons, neutrons and electrons in simple ions given the atomic number and mass number
• Atomic number = proton number = number of protons
• Mass number = nucleon number = number of protons + neutrons
• In an atom number of protons = number of electrons, but in an ion, there could be more or less protons/more or less electrons (i.e. if it is a cation with a 1+ charge, it has 1 more proton than electron and if it is an anion with a 1- charge, it has 1 more electron than proton) – use this information to determine the numbers of protons, neutrons and electrons in simple ions. Number of neutrons is no different from the equivalent atom.
##### 1.24 Explain the formation of ions an ionic compounds from their atoms, limited to compounds of elements in groups 1, 2, 6 and 7
• Ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0)
##### 1.25 Explain the use of the endings –ide and –ate in the names of compounds
• The names of some anions end in –ate or –ide, -ate suggests the presence of oxygen in the anion, e.g. carbonate, sulfate, nitrate, with the exception of oxide (and peroxide and hydroxide) – normally more than one oxygen
##### 1.26 Deduce the formulae of ionic compounds (including oxides, hydroxides, halides, nitrates, carbonates and sulfates) given the formulae of the constituent ions
• Oxide -> involves O^2- ion (e.g. sodium oxide: Na2O
• Hydroxide -> involves OH^ 1- ion (e.g. sodium hydroxide: NaOH)
• Halide -> involves a negative halide ion (e.g. sodium chlorIDE NaCl)
• Nitrate -> involves NO3^1- ion (e.g. sodium nitrate: NaNO3)
• Carbonate -> involves CO3^2- ion (e.g. sodium carbonate: NaCO3)
• Sulfate -> involves SO4^2- ion (e.g. sodium sulfate: NaSO4)
##### 1.27 Explain the structure of an ionic compound as a lattice structure: consisting of a regular arrangement of ions; held together by strong electrostatic forces (ionic bonds) between oppositely-charged ions
• A giant structure of ions = ionic compound
• Held together by strong electrostatic forces of attraction between oppositely charged ions
• The forces act in all directions in the lattice, and this is called ionic bonding.

An example is sodium chloride (salt):

Na+ (small blue particles) and Cl- (larger green ones)