Bonding Flashcards
What is ionic bonding?
- in ionic bonding, atoms lose or gain electrons to form charged particles called ions, which are then strongly attracted to one another (because of the attraction of opposite charges).
- this strong attraction is known as electrostatic attraction: it gives ionic compounds their high melting and boiling points
What is oxidation?
- when an atom loses electrons
What is reduction?
- when an atom gains electrons
Which groups of elements most readily form ions and why?
- groups 1, 2, 6 and 7
- their shells are nearly full or only have 1 or 2 electrons in the outer shell
What are cations and which groups of elements become them?
- positively charged ions
- groups 1 and 2 as they lose electrons
What are anions and which groups of elements become them?
- negatively charged ions
- groups 6 and 7 as they gain electrons
What happens when the cations collide with the anions?
- they attract each other to form an ionic compound
Why can only elements of opposites sides of the periodic table form ionic compounds?
- because one of them becomes a cation and the other an anion
- therefore, it’s between a metal and non-metal
What do compounds with ionic bonding always have?
- giant ionic structures
What is the structure of giant ionic structures?
- ions are held together in a closely packed 3D lattice arrangement by the attraction between oppositely charged ions
Describe the electrostatic attraction between the oppositely charged ions
- very strong
What are the properties of ionic compounds?
- high melting and boiling point
- brittle
- conduct electricity when molten or in solution, but not as a solid
Why do ionic compounds have high melting and boiling points?
- a lot of energy is needed to overcome the strong electrostatic attraction.
Why are ionic compounds brittle?
- if you hit it, ions of the charge move to become adjacent to each other
- so they repel
Why do ionic compounds only conduct electricity when molten or in solution?
- in a solid, ions are held in a lattice, so are not free to move
- in molten or solution, ions are free to move
How do the charges on the ions in the lattice affect the strength of the ionic bonding?
- the higher charge ions are held together by stronger forces of attraction
- they will also have higher melting and boiling points
How do you draw a diagram to represent the positions of ions in sodium chloride?
- draw one now
What is a covalent bond?
- atoms share a pair of electrons with other atoms to make full outer shell
What is the strength of attraction between the shared electrons and the nuclei in covalent bonding?
- a strong attraction
What are simple molecular/covalent substances?
- the atoms within a molecule are held together by very strong covalent bond
- talk about molecules!!
- however, the forces of attraction between the molecules (intermolecular forces) are very weak
What is the result of weak intermolecular forces?
- very low melting and boiling points
- the molecules are easily parted from each other
What are the properties of simple covalent substances?
- low melting/boiling point
- do not conduct electricity: there are no delocalised electrons or ions
What are giant covalent structures?
- a lattice of atoms that are joined by covalent bonds
- talk about atoms!! not ions or molecules
- all atoms are bonded to each other by strong covalent bonds
What are the properties of giant covalent structures?
- really high melting and boiling points: it takes a lot of energy to break them
- do not conduct electricity: except graphite
- usually insoluble in water
Give 3 examples of giant covalent structures
- diamond
- graphite
- silicon dioxide
Draw and describe diamonds
- each carbon atom forms forms four covalent bonds in a very rigid giant covalent structure
- very high melting point
- does not conduct electricity
- very hard because atoms cannot be broken. you would have to break very strong covalent bonds. used for cutting tools
Draw and describe graphite
- each carbon atom forms three covalent bonds, creating layers which are free to slide over each other
- strong covalent bonds within each layer
- conducts electricity: delocalised electrons between layers
- soft and flaky: layers of C atoms can slide over each other
- very high melting point
- used as lubricant, soft and slippery
What are giant metallic structures?
- a giant structure of positive ions surrounded by a sea of delocalised electrons
- the attraction between the positive ions and the electrons is called metallic bonding
Draw a metallic lattice
- have a lattice of cations, at least 3 x 3
- sea of delocalised electrons
What are the properties of giant metallic structures?
- conductors of electricity and heat as solid and liquid: delocalised electrons are free to move
- malleable: layers of cations can slide over each other,
- high melting point( not as high as ionic): strong electrostatic attraction between cations and delocalised electrons, so lots of energy to overcome it
