bonding, structure and properties of matter Flashcards
what are ions
charged particles, made when electrons lost or gained
what are metal and non metals ions called
cations (m) anions (n-m), non metals attract electrons more strongly than metals
what happens in ionic bonding?
-strong electrostatic attractions holds oppositely charged ions together in an ionic lattice
diatomic atoms:
Hydrogen, Oxygen, Bromine, Nitrogen, Chlorine, Iodine, Fluorine
ionic compounds:
giant ionic lattice very strong electrostatic forces of attraction betw opp charges ions in all directions
how to find empirical formula:
balance charges so overall is 0
properties of ionic compounds
-have high melting and boiling points due to strong electrostatic attraction betw ions. breaking them requires a large amount of energy
-most dissolve easily in water
-don’t conduct heat when solid because ions are held in fixed positions. when melted or dissolved, ions free to move so they’ll carry electric charge
dis and advantage of using:
dot and cross
3D models
ball and stick model
d&t:
-you can see electron transfer
-don’t show lattice structure, relative sizes of ions or how they are arranged
3D:
-show regular pattens and relative sizes of ions
-you can only see outer layer of lattice
b&s
-shows that crys is extended further than shown, shows pattern and relative size of ions and arrangement
-suggest that there are gaps between ions, sometimes ions not shown to scale
,
,
what is the formula of magnesium iodide?
mg forms 2+ ions and iodine forms 1- ions. to balance, two iodine is needed for each mg ion. so it’s MgI₂
what is covalent bonding?
describe
occur between non-metals
pair of elec shared betw two atoms.
+ charged nuclei of bonded atoms are attracted to the shared pair of elc by electrostatic forces , thus very strong bonds,
what is a double co bond?
two pairs of electrons shared between two atoms
what is a simple molecule? do they conduct electricity?
-made up of only a few atoms joined by covalent bonds
-they don’t conduct elec
-bcs no charged particles
properties of simple molecules
-don’t conduct electricity in any state, there are no ions or free electrons
-have low melting and boiling points (because of weak intermolecular forces which need to be overcome in order to melt, which doesn’t require much energy) so mostly gasses at room temperature, but can be solids
when is melting point higher?
larger or smaller molecules?
when the molecule is larger, intermolecular forces are stronger thus more energy required to break them
what is a polymer?
a substance ….
a substance consisting of long molecules
made of repeating sections
the atoms are joined by covalent bonds
how do you write molecular formula of polymer?
write molec formu of repeating unit by counting no. of atoms of each element it contains, put brackets around it and put an ‘n’ after the brackets
properties of polymer:
-higher melting and boiling points than simple covalent as intermollecular forces are stronger betw larger polymer molecules.
-most are solid at room temp
-however b&m points lower than ionic and covalent as inter mol is still weaker, so generally lower than cov and ionic
properties of giant covalent structures:
-have high melting and boiling points
-similar to lattices but charged ions
-ex diamonds and graphite, made up of only carbon atoms
what is an allotrope?
different structural forms of the same element in the same physical state
properties of graphite:
-each carbon atom only forms three covalent bonds,
-sheets of carbon atoms arranged in hexagons,
-no co bonds between layers, only held by weak intermolecular forces, so free to move,
-makes them soft and slippery ideal for lubricating material,
-high melting point,
-each carbon atom has one delocalised electron, graphite conducts electricity and thermal energy
properties of diamond:
-each carbon atom forms four covalent bonds with other carbon atoms,
-rigid structure,
-hard to break covalent bonds,
-no free ions or electrons so no electricity