subtopic 2.2 / bonding between atoms Flashcards
is energy involved in the formation and breaking of bonds?
yes, energy is released when bonds are formed and energy is required to break bonds.
define metallic bonding.
metallic bonding is described as the force of attraction between positively charged metal ions (cations) and their sea of delocalised electrons.
what are the properties of metallic bonds?
metals have low electronegativity values, meaning they are more willing to give away their valence electrons. Hence, within a metallic bond the ions are packed closely together and the electrons are free to roam between the metal cations.
melting and boiling points: there is a very strong attraction between the cations and the delocalised electrons contributing to metallic bonds having high melting and boiling points.
electrical conductivity: atoms are close together and the delocalised electrons are free to roam and carry electrical currents.
thermal conductivity: metals are good conductors of heat, the atoms vibrate faster as they are packed closely together and the heat thermal energy is easily passed on.
what is the structure of a metallic bond?
metallic bonds form a giant lattice structure of tightly packed metal cations, with delocalised electrons being able to roam freely and carry electrical charge.
what do malleable and ductile mean?
malleable: metals can be beaten into sheets.
ductile: metals can be drawn into wires.
define ionic bonding.
ionic bonding is the force of attraction between oppositely charged ions.
what are the properties of ionic bonds?
melting and boiling point: ionic bonds have high melting and boiling points due to their giant 3D lattice. The strong electrostatic attractions holding the 3D lattice in place means that a lot of energy is required to overcome these attractions.
electrical and thermal conductivity:
ionic compounds do not conduct electricity or heat in the solid state, as there are no electrons or ions free to move around. However, they do conduct electricity and heat in the molten and aqueous state as the lattice is broken and there are mobile ions present to carry the electrical and thermal current.
brittle: easy to break or snap.
define covalent compounds.
covalent compounds are formed when two or more non-metals share electrons.
- all small molecules are covalent molecular compounds, ie. methane and glucose.
what does VSEPR stand for?
Valence Shell Electron Pair Repulsion Theory, it determines the molecule’s 3D shape.
what are the various molecular shapes?
linear (2 electron domains), carbon dioxide
trigonal planar (3 electron domains)
tetrahedral (4 electron domains)
trigonal pyramid: a tetrahedral, with a lone pair of electrons.
v-shape: a tetrahedral with two lone pairs of electrons.
a covalent bond may be polar or non-polar. what is a polar molecule?
a polar molecule is formed when their is an electronegativity difference between the bonding atoms in the molecule and the molecule is asymmetrical.
all polar molecules are dipoles.
what is a non-polar molecule?
non polar molecules are formed when there is either no electronegativity difference between the atoms or the molecule is perfectly symmetrical.
what are the properties of covalent molecular bonds?
melting and boiling points: they have low melting and boiling points as a result of the weak forces of attraction between the molecules.
thermal and electrical conductivity: they are poor conductors of heat and electricity as the are generally gases and the molecules are spread far apart, making it difficult for the vibrations to pass from molecule to molecule.
difference between primary and secondary bonding.
primary bonds: bonds formed in the transfer or sharing of electrons.
secondary bonds: bonds that are caused by permanent or temporary dipoles within the atom or molecule.
difference between intramolecular forces and intermolecular forces.
intramolecular forces are forces that hold atoms within a molecule together.
intermolecular forces are forces that exist between atoms.
