compounds mixtures and chemical change
signs of chemical change
-one or more new chemicals are formed -energy is taken in or out during the reaction -the change is difficult to reverse
why do atoms form bonds
atoms bond with eachother in order to contain a full outer shell of electrons
cations
positive ions
anions
negative ions
ionic bonds
a strong electrostatic attractions between ions of opposite charge
how are ionic compounds formed
a metal atom loses an electron to a non-metal atom -this forms a positive metal ion and negative non-metal ion - they form a lattice -the compound has no overall charge
what cannot form ions
elements from group 4 and 5 -noble gases
how are ionic compounds made
the names of ions go together with the cation first
how to write formulas for ionic compounds
-write name for the ionic compounds -write down the symbols -the compound must have no overall charge
how are single covalent bonds formed
two atoms share electrons leading to full outer shells
what are diatomic elements
an element containing molecules with two or more molecules
solid iconic compounds properties
-held in tight lattice -lattice in each direction giving crystals -strong forces
solid molecular covalent compound properties
-weak forces in lattice -grow in all directions giving crystals -weak forces
properties of ionic compounds
-high melting point -usually water soluble -conduct electricity when melted or dissolved in water
properties of covalent compounds
low melting points -tend to be insoluble -do not conduct electricity
structure of metals
atoms are tightly packed together causing electrons to separate from them resulting in lattice of positive ions in a sea of electrons
metallic bonds
electrostatic attraction between positive ions and delocalised electrons
properties of metals
high melting points -conductors of heat and electricity