Presentation on theme: "To begin with... A recap on subshells. Electron subshell recap Question: Write out the full electronic subshell for the element: Si 1s 2 2s 2 2p 6 3s."— Presentation transcript:
Ions and metallic bonding To be able to work out the charge on different ions To know the properties of metallic bonding
Ions Ions are atoms or molecules that have lost or gained electron(s). Positively charged ions are known as cations – Just think, cats are great, really positive Negatively charged ions are called anions – No one likes onions... Metals lose electrons to become positive (cations) Non-metals gain electrons to become negative (anions).
If you see a Roman numeral after an element it usually means how many electrons it has lost. Transition metals can promote electrons within sub shells to lose varying numbers of electrons.
What charge will form? The easiest way to predict how many electrons will be lost or gained is to use the periodic table. Group 1 lose 1 electron Group 2 lose 2 electrons Group 6 gain 2 electrons Group 7 gain 1 electron This is because atoms are looking to fill/empty outer shells.
Quick task Can you predict how many electrons will be lost or gained by the following elements? – O – Cl – Al – Br – Na – Ca – H – Fe?
Electron subshell recap Question: Write out the full electronic subshell for the element: Si 1s2 2s2 2p6 3s2 3p2
Metallic bonding Metals tend to have high melting points and boiling points suggesting strong bonds between the atoms. Even a metal like sodium (melting point 97.8°C) melts at a considerably higher temperature than the element (neon) which precedes it in the Periodic Table. The simplest description of the bonding in metals consists of a lattice of metal cations in a sea of delocalised electrons. A metal atom releases its outer electrons into the sea, but its core electrons remain localised around its nucleus. This extensive delocalisation of valence electrons is responsible for most of the properties of metals.
There is an attraction between the positive cations and the negative electrons. The more negative electrons in the outer shell available to become delocalised, the stronger the bonding. There the higher boiling point. Which metal has a higher boiling point, sodium or magnesium?
What happens as you go down the group? More shielding from inner shells, therefore less of a positive charge to attract to the delocalised electrons. Therefore weaker intermolecular bonding Therefore lower melting points.