Bonding Flashcards
what is ionic bonding
Ionic bonding involves the transfer of electrons from a metallic element to a non-metallic element
how do ions form
Transferring electrons usually leaves the metal and the non-metal with a full outer shell
Metals lose electrons from their valence shell forming positively charged cations
Non-metal atoms gain electrons forming negatively charged anions
what forces are between ionic bonds
-strong electrostatic forces of attraction
- the strength depends on the charge and size
greater charge = stronger bond and smaller ions - more attraction bwt +ve and -ve ions
what is the structure of an ionic compound
crystalline lattice of +ve and -ve ions held together by an electrostatic force
this means the final lattice is overall neutral
what are the properties of ionic compounds
-high melting and boiling points. The melting and boiling points of ionic compounds is usually quite high because the ions in the giant ionic lattices are held together by strong electrostatic forces of attraction acting in all directions which are difficult to overcome. A large amount of energy is needed to break these forces (ionic bonds) therefore a high temperature is required.
Ionic compounds can only conduct electricity when molten or dissolved in solution.
-only conduct electricity when molten or dissolved because only then are the ions of the compound able to move and carry charge. Ionic compounds are unable to conduct electricity when solid because the ions are fixed in place and unable to carry charge.
-soluble in water. Ionic compounds easily dissolve in water which means they are highly soluble in water. This is because both ionic compounds and water molecules are partially charged molecules (polar). This means the partial charges of water break apart the ionic lattice, pulling oppositely charged ions apart and the ionic compound to dissolve.
-hard and brittle due to lattice
what is a covalent bond
a shared pair of electrons between non-metal atoms
why do they share electrons
to achieve a full noble gas electronic structure
how to guess covalent bonds
look at group number to see how many electrons are in the outer shell
what 2 types of molecules form in a covalent bond
-simple molecular-A simple molecule consists of a group of relatively few atoms joined together by strong covalent bonds.
-giant covalent -A giant covalent structure is where a large number of atoms are joined by covalent bonds.
simple molecular
-Simple molecules are held together by weak intermolecular forces. The atoms within a molecule are held together by strong covalent bonds but individual molecules are held together by weak intermolecular forces of attraction.
-Compounds with simple molecular structure have low melting and boiling points. When in its solid state, the simple molecules that make up the compound are arranged in a regular lattice held together by weak intermolecular forces. As these interactions are very weak, not much energy is required to overcome them, which results in simple molecular structures usually being gaseous or liquid at room temperature.
-Covalent compounds cannot conduct electricity. This is because there are no delocalised electrons to carry the current.
-insoluble in water
giant covalent
A giant covalent structure involves lots of covalent bonds present between several atoms which forms a giant lattice. As lots of covalent bonds are present in the compound, the structure is extremely strong
Compounds with giant covalent structure have high melting and boiling points. The large number of strong covalent bonds involved means that large amount of energy is required to break them apart.
Covalent compounds cannot conduct electricity. apart from graphite- This is because there are no mobile ions or electrons to carry the current.
types of carbon allotropes
diamond and graphite
fullerenes - buckminster and carbon nano
what are the properties of diamond
-In diamond, each carbon atom forms four covalent bonds with four other carbon atoms. In diamond, each carbon shares electrons with four other carbon atoms. This means that each carbon atom forms a single covalent bond with four other carbon atoms.
-Diamond is a very hard substance due to its strong covalent bonds. The strong covalent bonds in diamond means that it is very difficult to break. It is actually known to be the hardest naturally occurring substance found on Earth. As a result of its hardness, diamond is often used to coat drill bits.
-Diamond has a high melting and boiling point. The covalent bonds in diamond are very strong, therefore a large amount of energy is needed to break them.
-Diamond is a good conductor of heat. Diamond is a good thermal conductor because of the strong covalent bonds it consists of. This means that when you heat the diamond, the vibrations of thermal energy are rapidly transferred through the substance.
-Diamond is insoluble in both water and in organic solvents. Diamond does not dissolve in any solvent. This is because the attraction between the carbon atoms in diamond by covalent bonds is a lot stronger than the attraction that could occur between the solvent molecules and carbon atoms in diamond.
-Diamond is a poor conductor of electricity. Diamond cannot conduct electric because the outer electrons found in each carbon atom are fixated between the atoms in covalent bonds. This means there are no free electrons that can move around and carry charge
properties of graphite
-in graphite, each carbon atom forms three covalent bonds with three other carbon atoms. In graphite, each carbon shares electrons with three other carbon atoms. This means that each carbon atom has one outer electron that is not involved in a covalent bond. This ‘fourth’ electron becomes delocalised and is free to move around.
-The carbon atoms in graphite are organised into sheets of hexagons. In graphite, the carbon atoms are arranged into sheets which means that graphite has a layer structure. The sheets are arranged into layers and the layers are joined together by weak intermolecular forces called ‘van Der Waals forces’.
-Graphite is soft slippery substance because it consists of layers that can slide. Unlike diamond, graphite is arranged in layers and sheets of carbon atoms. The layers in graphite can easily slide over each other because there are weak intermolecular forces holding them together. Due to its slippery nature, graphite act be used in pencils and as a dry lubricant.
-Graphite has a high melting and boiling point. The covalent bonds in graphite are very strong, therefore a large amount of energy is needed to break them.
-Graphite is insoluble in both water and in organic solvents. Graphite does not dissolve in any solvent. This is because the attraction between the carbon atoms in graphite by covalent bonds is a lot stronger than the attraction that could occur between the solvent molecules and carbon atoms in graphite.
-Graphite is a good conductor of electricity. Graphite can conduct electricity because it contains delocalised electrons which are free to move between the sheets of carbon atoms and carry charge.
-Graphite has a low density because the distance between the layers is large. As the layers in graphite are held together by weak intermolecular forces, the layers are far apart.
what is a dative covalent bond
-one atom donates a pair of e-/both electrons to form a bond with a electron deficent atom
-Some molecules have a lone pair of electrons that can be donated to form a bond with an electron-deficient atom
-An electron-deficient atom is an atom that has an unfilled outer orbital
-So both electrons are from the same atom
-This type of bonding is called dative covalent bonding or coordinate bonding
what is an example of dative covalent bonding
Ammonium ion
The hydrogen ion, H+ is electron-deficient and has space for two electrons in its shell
The nitrogen atom in ammonia has a lone pair of electrons which it can donate to the hydrogen ion to form a dative covalent bond
what is a metallic bond
Metals have lots of delocalised electrons which make up a ‘sea’ of electrons.
Metal atoms are tightly packed together in lattice structures
The positive charges repel each other and keep the neatly arranged lattice in place
There are very strong forces between the positive metal center’s and the ‘sea’ of delocalised electrons
how do alloys form
If other atoms are added to the metal structure, such as carbon atoms, this creates an alloy
Alloys are much stronger than pure metals, because the other atoms stop the layers of metal ions sliding over each other easily- they distort the layers
how can the strength of electrostatic forces increase
The strength of the metallic attraction can be increased by:
Increasing the number of delocalised electrons per metal atom
Increasing the positive charges on the metal centres in the lattice
Decreasing the size of the metal ions
what are the properties of metals
-Metals have high melting and boiling points. The melting and boiling points of metallic compounds is usually quite high because the positive metal ions are strongly attracted to the delocalised electrons. This strong electrostatic force of attraction is difficult to overcome and a large amount of energy is needed to break it, therefore a high temperature is required.
-The more delocalised electrons present, the higher the melting point of the metal. As the number of delocalised electrons per metal atom increases, the melting point increases. This is because there is a greater electrostatic attraction between the positive ions and delocalised electrons and hence the metallic bond is stronger and requires more energy to break.
-Metals can conduct electricity and heat. Metals are good conductors of both heat and electricity because they contain delocalised electrons which are free to move around. Delocalised electrons can carry current as well as transfer kinetic energy between themselves.
-metals are insoluble in all solvents except liquid metals. Metals cannot dissolve in solvents because metallic bonds are very strong.
