Chemical Bonds (Ionic)
I. Kinds of Bonds:
A. Three types of chemical bonds you need to know
1. Ionic Bonds
2. Covalent Bonds
3. Metallic Bonds – Next Unit
A. Ionic Bonds: is the force of attraction between the opposite charges of the ions
in an ionic compound
1. What is an ion and an ionic compound?
a. Ion – Positively or negatively charged atom
b. Ionic Compound – compounds made up of 2 or more ions
c. How does an atom become an ion?
- An atom is considered electrically neutral if it has the
same number of electrons as protons. If for any reason the
atom loses or gains electrons the atom will have a charge
because the negative charge of the electrons will be
different than the positive charge of the protons
- Example: Magnesium 12 electrons and 12 protons
(+ 12 protons) + (– 12 electrons) = 0 or No Charge
If magnesium gained 2 electrons then:
(+12 protons) + (-14 electrons) = -2 or – Charge
d. How does an ionic bond form:
- an ionic bond forms when oppositely charged atoms
combine and there is a transfer of electrons
- Example NaCl: - Na has one electron in its valence shell
and wants to get rid of it
- Cl has 7 valence electrons and needs
one
- By Na transferring its one electron to
Cl,
- Na now has a complete valence shell;
and by Cl gaining one it also has a
complete shell.
- Ionic compound/bonds generally form between a metal
and non-metal.
Chemical Bonds (Covalent Bonds and Polar and Non-Polar Molecules)
A. Covelant Bonds:
1. Definition: The attraction that forms between atoms when they share electrons,
rather than losing or gaining electrons
2. Most atoms become stable by sharing electrons
a. Example: Cl2 Is this ionic or covalent, and how can you tell?
- Answer: Covalent because there is no charge
- Explanation: Each chlorine atom has 7 electrons in its valence
shell meaning they each only need 1 electron to
have a full set. However each chlorine atom can’t
give up one. So instead they will share an electron
to give each the full set of 8 electrons
b. Generally formed between non-metals, and non-metals and metalloids
B. Polar and Non-Polar Molecules
1. Atoms in molecules do not always share electrons equally
a. Electrons shared in a molecule may be more attracted to one atom than
the other
- Example: HCl
The chlorine atom has a stronger attraction for
electrons than hydrogen atoms do. So this
means the electrons will spend more time near
the chlorine atom than the hydrogen atom.
b. The uneven sharing gives the atoms in the molecule a slight but
opposite charge from one another
- In terms of HCl the chlorine atom has a slight negative charge
and the hydrogen a slight positive charge.
- When this occurs it is considered a Polar Molecule
Defined: A molecule that has a positive end and a negative
End
c. What happens when the atoms in a molecule share evenly?
- Example: N2 Neither nitrogen atom has a greater attraction for
electrons so the electrons will be shared evenly
- This causes the molecule not to have oppositely charged ends
- When this occurs it is considered a Non-Polar Molecule
Defined: A molecule that does not have oppositely charged
ends