Compounds
Review of Periodic Table
Compounds
The Periodic Table
Definitions:
Periods: horizontal rows of elements
Each period represents an energy level (electron cloud/circle)
Group (family): vertical column of elements with similar properties
The group tells you the number of valence electrons (in outer cloud) and the charge.
Ion: a charged atom in which the number of electrons is different from the number of protons.
Valence Electrons: electrons in the outermost shell
determine the reactivity
Compounds
Mettaloids: have properties similar to metals and non metals
Metals: anything to left of the mettaloids are:
malleable (can be hammered into shape)
ductile (can be stretched into wire)
good conductors of heat and electricity
lustrous (shiny)
NonMetals: anything to the right of the mettaloids line (and hydrogen) are:
brittle
insulators of heat and energy
Alkali Metals: located in column 1 (except for Hydrogen)
react with water to form alkaline solutions (need to be stored in oil)
feel softhave low melting points
Alkaline Earth Metals: column two
less reactive than Alkali metals
Halogens: in group 17
mix with group 1 to form a salt (example CL with Na)
Noble Gases: group 18
very unreactive and exist as single atoms
Transition Metals: middle of table
metals with less predictable properties
Compounds
Compounds
1. Draw the nucleus as a solid circle.
2. Put the number of protons (atomic number) in the
nucleus with the number of neutrons (atomic mass –
atomic number) under it.
3. Place the number of electrons (same as protons) in
the electron clouds around the nucleus by drawing
circles around the nucleus.
1st shell – 2 electrons,
2nd shell – 8 electrons,
3rd shell 18 electrons
n=shell number # of electrons = 2(n^2)
Periods (rows) = # of electron clouds (outer cloud
valence cloud)
Groups (columns) = # of valence electrons
Compounds
atomic number=number of protons
# of protons = 15
# of neutrons =
mass number protons
3115=16
There are 16 neutrons
mass number
1. Draw the nucleus as a solid circle.
2. Put the number of protons (atomic number) in the
nucleus with the number of neutrons (atomic mass –
atomic number) under it.
3. Place the number of electrons (same as protons) in
the electron clouds around the nucleus by drawing
circles around the nucleus.
1st shell – 2 electrons,
2nd shell – 8 electrons,
3rd shell 18 electrons
Periods (rows) = # of electron clouds circles
P is in the 3rd row, therefore 3 circles must be drawn.
Groups (columns) = # of valence electrons (outer circle)
15 P
16 N
15 P
16 N
Compounds
Bohr Diagram Worksheet
Compounds
Compounds:
made of 2 or more elements chemically combined through a chemical reaction
when atoms join, they do so in specific amounts or proportions to form a molecule (smallest part of a compound.)
example: a water molecule always consists of 2 atoms of hydrogen joined to an atom of oxygen.
Compounds have properties that are not like their component elements.
example: oxygen and hydrogen are both gases at room temperature, but chemically combine to make a liquid at room temperature.
All compounds of chemical names.
water=dihydrogen oxide
Salt=sodium chloride
The Chemical Formula contains the symbol for each element in the compound and shows the number of each atom.
carbon dioxide= 1 atom of carbon joined to 2 atoms of oxygen.=CO2
Compounds
How are chemical compounds formed?
Chemical compounds are the result of the chemical bonding of atoms.
chemical bond: the forces that attract atoms to each other in compounds.
elements combine or bond together because of their valence electrons (valence electrons are in the outer shell of an atom.)
Octet Rule: every atom of every element wants to have 8 electrons in its outer shell.
Compounds
Finding the Ionic Charge:
Ionic Charge of a Metal:
A metal LOSES electrons.
This means a metal has a positive ionic charge.
The ionic charge is the number of electrons the atom
wants to give away.example: K (Potassium)
K has 1 valenceshell electron.
K gives away this single electron.
The ionic charge of potassium is +1.
We write this as: K+1
Ionic Charge of a NonMetal:
Look at the number of electrons in the outer shell. Calculate
how many more electrons that atom needs to have 8. That number is the ionic charge with a minus charge.
example: Oxygen has 6 valence electrons.
Oxygen needs 2 more to have 8. Therefore oxygen wants
to borrow/gain these 2 electrons. The ionic charge of Oxygen is 2.
We write this as O2
Compounds
Ionic Compounds: formed with ionic bonds
(donation of electrons)
Made of metal elements andnonmetal elements.
can have a positive charge:cation (loses valence e)can have a negative charge:anion (gains valence e)attraction is strong between opposite charged particles.
Covalent Compounds: formed with covalent bonds (sharing of e)Made of only nonmetal
elements.
can have a positive charge:cation (loses valence e)can have a negative charge:anion (gains valence e)attraction between molecules
is weak
Compounds