Transcript 22.2 – Types of Bonds - Trimble County Schools

2/27/12 - Bellringer
 What is the
joke in this
comic?
Atomic Structure Review
 Atoms are
made up of
protons,
neutrons, and
electrons
 Individually,
atoms have the
same number
of p+ and e-
Atomic Structure Review
 If an element has 8 protons, how many
electrons does it have?
 If an element has 53 electrons, how
many protons does it have?
Atomic Structure Review
 The number of electrons in an atoms
valence shell is NOT the total number of
electrons in that atom (except for H and
He)
 Valence shell = outer electron shell
22.2 Notes –
Types of Bonds
Objective
 Describe ionic and covalent bonds
Ion
An atom that has lost or gained
electrons
A
charged particle because it has
more or fewer electrons than protons
Atoms lose or gain to meet a
standard—a stable energy level
 Sports drinks – Electrolytes = ions in found in
blood
How bonds form
The positive and negative
charges are not balanced on
their own
It is the electric forces between
oppositely charged particles that
hold compounds together
A Bond Forms - KI
A neutral atom of potassium has
one electron in its outer level
 Not
a stable outer energy level
Potassium often forms
compounds with halogens
 Alkalis
(Group 1) often form
compounds with Halogens
(Group 17 / 7A)
Potassium atom has become
an ion
 Loses
an electron (drops one
energy level), becomes positively
charged
 One less electron in the atom
than protons in the nucleus
Ion = K+

The 1+ charge is shown as a
superscript written after the element’s
symbol to indicate its charge
Iodine atom also undergoes a
change
 Iodine
has 7 electrons in its outer
energy level
 Iodine atom wants to gain an
electron to fill its outer energy
level
 No longer neutral because it has
gained an extra negative particle
Has a charge of –1 and is called
a iodide ion, written as I-
 Cation = positive ion

Loses electrons
 Anion = negative ion

Gains electrons
Potassium iodide
Ionic Bonds
 When ions attract due to their opposite
charges
 In an ionic bond a transfer of one or more
electrons takes place and large amounts of
energy are released

If an element loses electrons, one or more
elements must gain an equal number of
electrons to maintain the neutral charge

http://www.youtube.com/watch?v=c-nMmwfTV-w
Formation of Ionic Bond
 Magnesium reacts with chlorine
 Magnesium atom loses 2 electrons and becomes
a positively charged ion, Mg2+
 Two chlorine atoms gain one electron each and
become negatively charged ions, Cl-
Ionic Bonds
 Zero net charge = Neutral compound

Positive charge balances with negative
charge
 Metal + nonmetal
 Elements on opposite sides of periodic
table