Physical Science: Ch 6 Notes
A. Atoms Bond to form Compounds
Compound- a substance that is composed of two or more different
elements joined in a fixed proportion
Chemical bond- the force that holds atoms together
Covalent bond- a chemical bond in which two atoms (both
nonmetals!) share a pair of valence electrons
Ionic bond- a chemical bond that forms between atoms of a
metal and a nonmetal
Form when electrons are transferred from one atom to another
This transferring of electrons allows electricity to flow through
solutions of ionic compounds
Results in the formation of ions – atoms that have a net positive
or negative electric charge
This charge is due to the loss or gain of electrons
Physical Science: Ch 6 Notes
Cation – an ion with a positive charge (due to loss of electrons)
Anion – an ion with a negative charge (due to gain of electrons)
Naming ionic compounds
examples:
magnesium chloride
copper sulfide
zinc oxide
the trend:
cation anion-ide
Molecule – a neutral group of atoms (nonmetals!) that are joined
together by one or more covalent bonds
The attractions between the shared electrons and the protons
in each nucleus hold the atoms together in a covalent bond
Molecules are named using prefixes that describe
the number of atoms of each element in the
molecule
Physical Science: Ch 6 Notes
Prefixes for naming COVALENTLY bonded molecules:
1=mono
6=hexa
2=di
7=hepta
3=tri
8=octa
4=tetra
9=nona
5=penta
10=deca
Examples:
NOTICE:
N2O4 is dinitrogen tetraoxide
P3F7 is triphosphorus heptafluoride
NO2 is nitrogen dioxide
the second element still ends in –ide
the prefix mono is not usually used for the first
element in the name (NO2 is nitrogen dioxide)
REMEMBER: When naming chemicals, prefixes are only
used when nonmetals are bonded (COVALENT
MOLECULES)! Prefixes are NOT used for naming Ionic
Compounds.
Physical Science: Ch 6 Notes
B. Properties of Ionic and Covalent chemicals
IONIC
COVALENT
-usually solid at room temperature
-usually liquid or gas at room temp
-have high melting and boiling
points
-lower melting and boiling points
-forms solid crystals
-does not form solid crystals
-solutions of ionic compounds
conduct electricity
-solutions do not conduct electricity
-usually dissolve in water very well -usually do not dissolve in water very
well
Physical Science: Ch 6 Notes
C. Metals
Alloy – a mixture of two or more elements, at least one of which is a metal
Bronze – alloy of copper and tin metals
Brass – alloy of copper and zinc metals
Steel – alloy of iron with small quantities of carbon