Name: ______________________________________ Period: _________
26
Stability in Bonding
Ch 19, Page 574
A chemical formula tells us what elements are contained in a compound, and the exact number
of atoms there are in a unit of that compound.
Ex – H20 = 2 atoms of Hydrogen and 1 atom of Oxygen
Oxygen
Hydrogen
Hydrogen
The small number after an element’s symbol is called a subscript.
•
The subscript identifies the number of atoms of the element that comes BEFORE it.
SiO2 is made of 1 atom of silicon and 2 atoms of oxygen
HC2H3O2 (vinegar) is made of 4 atoms of Hydrogen, 2 atoms of Carbon, and 2 atoms of oxygen.
Atoms form compounds because they want to become more stable.
A chemical bond is the force that holds atoms together in a compound.
All atoms want 8 valance electrons, and they will share electrons with other elements in
order to reach the goal of 8.
Group 1 will bond with Group 17
Group 2 will bond with Group 16
The Nobel gases (group 18) are the only elements who naturally have 8 valence electrons.
They will never form compounds and are considered INERT (non reactive).
Types of Bonds (page 580)
Atoms gain or lose electrons in order to become more stable (to reach 8 valence
electrons).
An Ion is an atom that has gained or lost an electron.
Ions are charged particles because their number of electrons no longer equals their
number of protons.
Name: ________________________________________ Date: ______________________
Ions
Potassium
Potassium Ion (K+) – has more protons than electrons.
(as appears on Periodic Table)
When it gives away an electron during bonding, potassium becomes positively charged because
there are 19 protons but only 18 electrons.
We write the potassium ion like this:
The + sign indicates a positive charge.
K+
Ionic Bonds
Ionic bond – a bond between elements of opposite charges.
Na has 1 valence electron
Chlorine has 7 valence electrons
The 2 elements are attracted to each other
Na gives its valence electron to Cl. Now both join
to form the compound NaCl. They are held
together by an ionic bond.
Since the charges balance one another, the overall
compound is neutral.
Covalent Bonds
Another way atoms can reach the magic number of 8 valence electrons is by sharing electrons.
Hydrogen has 1 valence electron
Oxygen has 6 valence electrons.
They are attracted to one another and share electrons so
that each has 8 total.
Covalent bonds are made when atoms share electrons. The
result of a covalent bond is a molecule.
Sometimes molecules have atoms that don’t share their electrons equally. A molecule that has a
slight positive charge at one end and a slightly negative charge at the other is called a polar
molecule. Water is POLAR.
A non-polar molecule does not have a charge.
In short:
COVALE NT compounds form between nonmetals.
IONIC compounds form between metals and nonmetals.
Metals form positive ions
Nonmetals form negative ions.
Name: _______________________________________ Period ____________
26
Stability in Bonding
Ch 19, Page 574
A __________________________________ tells us what elements are contained in a compound, and
the ___________________________________________________ there are in a unit of that compound.
Ex – H20 = _________________ of Hydrogen and _____________ of Oxygen
___________
___________
___________
The small number after an element’s symbol is called a _____________________.
•
The subscript identifies the ________________________ of the element that comes
________________ it.
SiO2 is made of _____________________________________________________________________________
HC2H3O2 (vinegar) is made of __ atoms of Hydrogen, ___ atoms of Carbon, and ___ atoms of
oxygen.
Atoms form compounds because
________________________________________________________________.
A _____________________________________ is the force that holds atoms together in a compound.
All atoms want ________________________________, and they _____________________________
with other elements in order to reach the goal of 8.
______________ will bond with ______________
_____________ will bond with _______________
The Nobel gases (group 8) are the only elements who
_______________________________________.
They ______________________________________________________.
Types of Bonds (page 580)
______________________________ in order to become more stable (to reach 8 valence
electrons).
An ______ is an atom that has gained or lost an electron.
Ions are ___________________________ because their number of electrons no longer equals
their number of protons.
Ions
________________________ – has more protons than electrons.
When it gives away an electron during bonding, potassium becomes
______________________________ because there are 19 protons but only 18 electrons.
We write the potassium ion like this:
The __ sign indicates a positive charge.
Ionic Bonds
Ionic bond - a bond between elements of ________________________________________.
Na has ___________________________________
Chlorine has _____________________________
The 2 elements are __________________ to each
other
___________________ its valence electron to Cl.
Now both join to form the compound NaCl. They
are held together by an _____________________.
Since the charges balance one another, the overall
compound is ___________________.
Covalent Bonds
Another way atoms can reach the magic number of 8 valence electrons is by
______________________.
Hydrogen has ________________________________________
Oxygen has ___________________________________________.
They are attracted to one another and ________________________
so that each has 8 total.
________________________________ are made when atoms share
electrons. The result of a covalent bond is a ___________________.
Sometimes molecules have atoms that don’t share their electrons equally. A molecule that has a
slight positive charge at one end and a slightly negative charge at the other is called a
__________________________________________.
A _____________________________ molecule does not have a charge.
In short:
COVALE NT compounds form between nonmetals.
IONIC compounds form between metals and nonmetals.
Metals form positive ions
Nonmetals form negative ions.