Chapter 3 - Bonding Flashcards
What are negative ions called?
Anions
What is an ionic bond?
The electrostatic atteaction between oppositely charged ions
Why do ionic compounds have a high melting/boiling point?
The energy required to melt an ionic solid is large due to the large number of strong electrostatic attractions between the positive and negative ions.
Why are ionic compounds usually soluble in water?
Water likes charged substances and likes to surround the ions that have broken out of the lattice. When the moving water molecules hit the ionic lattice they can knock off ions and water molecules surround the ions
Why do ionic compounds conduct electricity when molten or whenin aqueous solution?
In a liquid or aqueous state, ions are free to move and carry charge
What is a covalent bond?
A covalent bond consists of one or more shared pairs of electrons between two atoms
What are positive ions called?
Cations
What are covalent bonds found in?
- Molecular elements and compounds (e.g. Cl2, P4, CO2)
- macromolecular covalent elements (e.g. Graphite, diamond)
- molecular ions (NH4+ , NO3-)
What is a coordinate bond?
A coordinate bond contains a shared pair of electrons with both electrons supplied by one atom
What is a metallic bond?
A metallic bond is the electrostatic attraction between the delocalised electrons amd the positive metal ions in the lattice
What are the properties of ionic compounds?
High melting points
Soluble in water
Conduct electricity in water
What are the properties of metals?
- Metals conduct electricity
- Metals conduct heat
- Metals are ductile and malleable
- Metals have high densities
- Most metals have high melting points
Explain why metals conduct electricity
There are delocalised electrons in the metal structure and these electrons can move. An electric current flows because of the movement of electrons or charged particles. These delocalised electrons can carry the charge.
Explain why metals conduct heat
The delocalised electrons in the metal structure enable heat energy to be passed through the metal
Explain why metals are ductile and malleable
Metals have a layered structure, these layers can slide over eachother without disrupting the bonding
Explain why metals have high densities
In metals the positive ions are packed tightly together and so the density is high.
Why do most metals have high melting points?
Metals have a large regular structure with strong forces of attraction between the positive ions and delocalised electrons. A large amount of energy is required to break these attractive forces
What are the propeties of molecular covalent crystals?
- Molecular covalent crystalline substances have low melting points
- Brittle because they don’t have strong bonds holding them together
- Don’t conduct electricty as there are no charged particles
What are allotropes?
Different forms of the same element in the same physical state
What are the properties of diamond?
- Very hard
- High melting point
- Each carboj strongly bonded to four others in a tetrahedral arrangement
- Doesn’t conduct heat or electricity because there are no charged particles
What are the properties of graphite?
- Conducts electricity
- High melting point
- Layered structure with weak forces of attraction
- Each carbon atom attached to three others in a hexagonal arrangement
What is the bond angle of a trigonal planar shape?
120 e.g. BF3
What is the bond angle of a tetrhedral shape? E.g. CH4
109.5
What is the bond angle of a pyrimadal shape? NH3
107
What is the bond angle of a bent shape? E.g. H20
104.5
What is the bond angle of a trigonal bipyrimid? E.g. PF5
90 and 120
What is the bond angle of a t shaped shape? E.g. BrF3
86
What is the bond angle of a octahedral shape? E.g. SF6
90
What is the bond angle of a square planar? E.g. BrF4-
90
What is the definition of electronegativity?
The electronegativity of an element is the power of an atom to attract the pair of electrons in a covalent bond
What three factors is electronegativity dependant on?
- Atomic radius
- Nuclear charge
- Shielding
What is the atomic radius?
The distance of the bonding electrons from the attractive power of the nucleus
What does shielding mean?
The attractive power of the nucleus being shielded by inner electrons
