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INTRODUCTORY CHEMISTRY
Student Worksheet – Week three.
Draw electron shells diagrams for various elements.
Explain the terms; elements, compounds.
Elements and compounds
Elements are substances that contain only one type of atom. Hydrogen gas is
an element as it contains only hydrogen atoms. Compounds contain the atoms
of two or more different elements joined together. Water is a compound that
consists of hydrogen and oxygen atoms joined together. There are nearly 100
different, naturally occurring elements. They are arranged into a table called the
periodic table.
Atoms are made up
of electrons,
protons and
neutrons. A typical
atom looks like the
one on the right.
If you look at a PERIODIC TABLE, you will see that different elements have
different ATOMIC NUMBERS. The atomic number is the number of protons in
each atom of that element. The number of protons equals the number of
electrons for normal atoms.
The way that electrons are arranged in atoms is very important. Diagrams can be
used to show the arrangement of electrons in atoms.
HYDROGEN
SODIUM
CHLORINE
OXYGEN
© Peter Adams 2006
MAGNESIUM
HELIUM
Atoms don’t like to have partially filled shells. They like to be like Neon; having
their shells either totally full, or totally empty. Atoms lose or gain electrons to
empty or fill the shells.
Sodium will lose one electron and become Na+
Oxygen will gain two electrons and become O2Magnesium will ________ _______ electrons and become ______
Chlorine will ________ ________ electron and become ______
Charged atoms, or groups of atoms, like Na+, Mg2+, O2- & Cl- are called IONS.
POSITIVE IONS
NEGATIVE IONS
Name
Symbol
Name
Symbol
Hydrogen
Mercury (II)
Sodium
Silver
Potassium
Ammonium
Barium
Calcium
Lead
Copper (I)
Copper (II)
Magnesium
Iron(II)
Iron(III)
Zinc
Aluminium
H+
Hg2+
Na+
Ag+
K+
NH4+
Ba2+
Ca2+
Pb2+
Cu+
Cu2+
Mg2+
Fe2+
Fe3+
Zn2+
Al3+
Chloride
Sulfide
Sulfate
Sulfite
Hydroxide
Oxide
Nitrate
Nitrite
Ethanoate
Phosphate
Carbonate
Bicarbonate
Iodide
Peroxide
Fluoride
Bromide
ClS2SO42SO32OHO2NO3NO2CH3COOPO43CO32HCO3IO22FBr-
© Peter Adams 2006