Structure and bonding Flashcards
what takes place at the melting point of a solid
-freezing and melting
what takes place between a lquid and a gas at the boiling point
condensing and boiling
what does the amount of energy needed to change state depend on
strength of forces between the particles of the substance
the stronger the forces between the particles…..
the higher the melting point and boiling point
gas particles
- widely spaced
- constant quick motion
- collisions are frequent and elastic
- weak forces between the particles
liquid particles
closely spaced
still in constant motion
constantly colliding
forces between particles less stronger than in solids
solid particles
do not move around freely
vibrate in a fixed position only
the simple model
small solid spheres
limitations of this model are that there are no forces between the particles shown
atoms molecules and ions are not solid spheres
what do pure elements and compounds boil at
specific temperatures
a pure substance will:
melt or boil at a specific temperature
whereas a mixture melts or boils over a range of temperatures it does not have a sharp melting point.
solid melting curve
-temperature rises when solid starts to melt
a pure solid will melt at a fixed temperature and the line will stay horizontal when its melting
the temperature does not rise when the solid is melting because heat absorbed to break the bonds between solid particles
ionic bonding between a non metal and a metal
when a metal atom reacts with a non metal atom, electrons in the outer energy level are transferred
metal atoms
metal atoms lose electrons to form positive ions
and non metal atoms gain electrons to form negatively charged ions
ions produced by metals in group 1 2 and non metals in 6 and 7
have the electronic structure of a noble gas
sodium chloride example
in sodium chloride sodium atom loses one electron away forming a 1+ ion the chlorine atom gains one electron to form a 1- ion
the ionic bond is the force of attraction between the oppositely charged ions.
ionic compound
total positive charge should be the same as the total negatuve charge
compound ions
some groups of elements have a charge- these are called compound ions
carbonates- co3 2- , sulfates so4 2- mitrates no3 -
ammonium nh4+
when to use brackets
when more than one compound ion is used in a formula we put the ion inside in brackets and put the number outside brackets.
giant ionic structure
an ionic compound is a giant structure of ions
ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. these forces act in all directions in the lattice this is called ionic bonding
there are two models to present ionic bonding
space filling
ball and stick model
advantages and disadvantages of ball and stick
advanatages- shows electrostatic forces of attraction
allows to clearly see ions in 3 dimensions
disadvantage- does not show sizes of ions correctly ions are shown as spaced when in reality they are much closer together.
space flling
advantages and disadvantages
sizes of each ion shown correctly shows how closely packed ions are
disadvantages- electrostatic forces of attraction are not shpwn
both only show
both ball and stick and space filling models only show a tiny part of the crystal lattice both give a mistaken impression on sizes of these structures
properties of ionic compounds
high melting points
high boiling points
because large amounts of energy required to break the strong electrostatic forces of attraction between the oppositely charged ions
