Question of the Day
9-17
Use your periodic table and tell me
everything you can about oxygen (for
example, how many protons does it
have? what’s its atomic #? etc.).
Objectives
Explain the formation of compounds
(ionic and covalent) and their resulting
properties using bonding
theories
SIDE NOTE:
The Periodic Table
WHAT CAN WE TELL FROM THE P.T.?
Atomic Number = Number of protons
Mass Number = Number of protons +
neutrons
Isotopes = Atoms of the same element with
different number of neutrons
– EX: Carbon-12, Carbon-13, & Carbon-14
Atomic mass = the masses all the isotopes
of an element are averaged and that is the
atomic mass on the periodic table
The Periodic Table
WHAT CAN WE TELL FROM THE P.T.?
In a neutral atom # of electrons = # of
_________.
protons
An element’s group determines its
____________________!
valence
electrons
G
R
O
U
P
S
P E R I O D S
He, Ne, and Ar are in the same
_____________ (group 18).
C, N, and O are in the same
_____________ (period 2) .
The Octet Rule
Octet rule – Atoms tend to gain,
lose, or share electrons in order to
acquire a full set of valence
electrons (8 for most elements, 2 for
H, He, Li, Be, + B)
Ions – Atoms that have lost or
gained electrons in order to achieve
the octet rule (become stable)
The Octet Rule
Ions – Atoms that have lost or
gained electrons in order to achieve
the octet rule (become stable)
If an atom GAINS
________ negative electrons
it becomes _____________
NEGATIVE
If an atom _________
LOSES negative
electrons it becomes POSITIVE
____________
Quick Talk
Proton
Electron
Biosphere
Homeostasis
Element
Compound
Neutron
Octet rule
Ion
Valence electrons
Isotope
Question of the Day
Explain why atoms form ions (you
might have to start by looking up
ion).
9-21
Atoms tend to gain or lose electrons
in order to acquire a full set of
valence electrons (8 for most
elements, 2 for H, He, Li, Be, + B)
= Octet rule
1. Record your grade (%) _________
2. How did you prepare for the quest?
9-21
3. What do you plan to do to prepare for next test.
4. Set a goal for next time:
If you got an A (92-100%): You must
improve at least 1 percentage points.
If you got a D, C, or B (65-91%): You must
improve at least 3 percentage points.
If you did not pass (64% or less): You must
improve to at least passing (65%).
What happens when atoms collide?
Valence electrons interact.
Question of the Day
9-22
When two elements share valence
electrons they form a
chemical bond
________________.
Objective
9-22
Explain the formation of
compounds (ionic + covalent)
and their resulting properties
using bonding theories.
1, 2, 3 Questions
Are there chemical bonds
with more than 2 atoms?
What is a pure substance?
What else are we going to
learn in this chapter?
1, 2, 3 Questions
Why do atoms bond?
How do you find electrons?
Do beans grow better in the
sunlight or dark?
1, 2, 3 Questions
Why do neutrons have a
neutral charge?
In a dot diagram, how can
you tell how many valence
electrons there are on each
side of the chemical symbol?
Chemical bond – A mutual electrical attraction
between the nuclei and valence electrons of
different atoms that binds them together …
electrostatic force
positive
Nuclei = _______________
charge
Electrons = _______________
negative
charge
9th pd 9-21
Opposites Attract!!!
But Why Bond at all?
Atoms Generally want 2 (H,
He, Li, Be, and B) Or 8
Electrons and they can
share (bond) to get them!!!
~ octet rule
Why bonds and ions?
Achieving electrical and energetic
stability.
Lone electrons – high
potential energy - BAD
Electron pairs –
stable - Good
Br
3 main bond types:
• Ionic
• Polar covalent
• Nonpolar covalent
Ions – charged particles
Collision – Ions
(-)
Br
Li
BANG
(+)
Li
Br
But they don’t separate …
WHY?
+
-
Li Br
Li
BANG
Br
Ionic bonds – Chemical bonds
that result from the electrical
attraction between large numbers
of positive and negative ions –
opposite charges attracting
Ionic bonds most commonly
form between metals and
nonmetals!
Ions break apart in water and
form a solution that conducts
electricity
Covalent bonds - Chemical bonds that
result from the sharing of electron pairs
between two atoms
What is the difference between
ionic and covalent bonds?
Ionic bonding
the result of electrical attraction
Unequal charge distribution (ions)
covalent bonding
based on sharing of electrons
Equal charge distribution (NO ions)
Molecule – group of atoms united by
covalent bonds (molecules =
molecular substance)
Ionic - Empirical = ratio
Molecular - How many atoms in a
single molecule (not
always a simplified ratio,
sugar = C6H12O6)