Atomic structure, the periodic table, bonding, properties of matter Flashcards
what is a chemical bond?
a force of attraction
describe a covalent bond
pair of electrons are shared between non-metal atoms to gain full outer shells
what is the IMF between molecules in simple covalent substances?
weak
what is the usual state of simple covalent substances and why?
gases and liquids - IMF broken in state change
what is the BP of simple covalent substances?
low BP
what is the charge of simple covalent substances?
neutral charge (doesn’t conduct electricity)
what is the formula type used for simple covalent substances?
molecular
a bigger molecule has what type of IMF and MP?
stronger intermolecular forces - higher melting point
what is the state of giant covalent substances?
solids
what is the MP of giant covalent substances?
very high melting point
what is the atomic structure of giant covalent substances?
all atoms bonded to others by strong covalent bonds which must be overcome to boil/melt these substances
what is the formula type of giant covalent substances?
empirical
describe a metallic bond
- atoms in metals are tightly packed in layers - giant 3D lattices
- outer electron(s) from each atom is delocalised & is able to move through the structure
- each metal ions is equally attracted to delocalised electrons by electrostatic forces of attraction
describe an ionic bond
- metals react with non-metals
- electrons are transferred from the outer shell of metal atoms to the non-metal atoms, to get a full valence shell
- strong electrostatic force of attraction between oppositely charged ions
what are the properties of ionic substances?
- high melting points as there are strong forces between ions - lots of energy needed to break/overcome them
- solid at room temperature
- do not conduct electricity as solids
- conduct electricity when molten or in solution - as solid, ions in fixed positions and cannot move so cannot carry charge. when molten/dissolved, ions free to move & can carry charge
describe the structure of ionic compounds when dissolved in water
water causes the giant lattices to break apart so ions become individual and are free to move.
what are ions?
electrically charged particles with a different number of protons and electrons
why do metals form positive ions?
it is easy for them to lose electrons as they have a small number of electrons in the valence shell
what does ion charge correspond to?
group number (for 1=1+ 2=2+ 3=3+ 5=3- 6=2- 7=1-)
what is a pro of the dot-cross diagram?
shows the electron structure of the ions
what is a con of dot-cross diagram?
can give the impression that the structure is made of pairs of ions, rather than being a continuous structure containing a massive number of ions
what is a pro of the ball and stick structure?
helps to show how ions are arranged relative to each other
what are some cons of the ball and stick structure?
- the lines connecting ions may be confused with covalent bonds
- it may be thought that ions are far apart from each other
what is pro of the 3D space filling structure?
gives a very good representation to how ions are packed together