Hidden Info in the
Families & Periods
• Columns are known as Groups or Families
– Elements in a given family share similar
properties
– Reactivity increases as you go down a
column
• Rows are known as periods
Bohr Model of Atoms
Bohr Model for
Lithium
• Also known as the
planetary model
• Depicts electrons around
the nucleus like planets
around the sun
• Electrons in orbitals or
shells
• As each orbital is filled
electrons move to further
orbitals
Electron Orbitals
• First orbital can hold 2 electrons
• Second orbital can hold 8 electrons
• Third orbital can hold 8 electrons until
Argon (Period/Row 3)
– After Argon, things get a bit funky and more
electrons can fit in the third orbital
Period 3 vs Period 4 Orbitals
Electrons in Orbitals
The outer-most orbital can only ever hold 8
electrons – the octet.
Other larger orbitals are nested inside.
Orbital 1
Orbital 2
Orbital 3
Orbital 4
Orbital 5
Orbital 6
Period 1
2
Period 2
2
8
Period 3
2
8
8
Period 4
2
8
18
8
Period 5
2
8
18
18
8
Period 6
2
8
18
32
18
8
Period 7
2
8
18
32
32
18
Orbital 7
8
Valence Electrons
• Families are organized by number of valence
electrons
• Valence electrons are the number of electrons
in the outermost orbital
– Maximum number of valence electrons is 8 (Octet
Rule)
– Valence electrons determine the reactivity of an
element
– Also determine if elements are more likely to be
positively charged (cations) or negatively charged
(anions)
• In the periodic table, all elements in the
same group/family/column have the same
number of valence electrons.
How Many Valence Electrons in the
Following Element?
• Therefore what group
is it in?
Lewis Dot Structures
• The chemical symbol
for the atom is
surrounded by a
number of dots
corresponding to the
number of valence
electrons
• Lithium has 1 valence
electron so draw 1 dot
Li
• Carbon has 4 valence
electrons so draw
how many dots?
C
Ions
• Atoms will gain and lose electrons to
reach a stable octet
Group 1A – Alkali Metals
• Have 1 valence electron
• Most reactive metals
• Soft and can be cut with a
knife
• Never found in a pure
state in nature because
they are so reactive
• React explosively with
water!
• MythBusters version
• Like to lose 1 valence
electron easily to
become positively
charged (+1 cation)
Group 2A – Alkaline Earth Metals
• Have 2 valence
electrons
• Not as reactive as Alkali
metals
• Have higher melting and
boiling points
• Like to lose 2 valence
electrons and become
positively charged (+2
cations)
• Never found pure in
nature
Group 3A – Boron Family
• Have 3 valence
electrons
• Contain both
metalloids (Boron)
and soft-silvery
metals
• All have high melting
points
• Easily lose 3
valence electrons
Group 4A – Carbon Family
• Pure Carbon
• Have 4 valence
electrons
• Contain 1 nonmetal
(carbon), 2 metals (tin &
lead), and 2 metalliods
(silicon & germanium)
• All living things contain
carbon
• Can either gain or lose
4 electrons
Group 5A – Nitrogen Family
• Have 5 valence
electrons
• Like to gain 3
electrons
Group 6A – Oxygen Family
• Have 6 valence
electrons
• Like to gain 2 electrons
to become negatively
charged (-2 anion)
• Oxygen produced by
plants over geologic time
has contributed the
oxygen to the Earth's
atmosphere which
sustains life.
Group 7A - Halogens
• Have 7 valence
electrons
• Highly reactive
• Like to gain 1 electron
to become negatively
charged (-1)
• They can exist in all 3
states of matter:
– Solid- Iodine, Astatine
– Liquid- Bromine
– Gas- Fluorine, Chlorine
Group 8A – Noble Gases
• Have 8 valence
electrons
• Do not readily combine
with other elements to
form compounds, the
noble gasses are called
inert
• Extremely unreactive
because their
outermost orbital is full
• All noble gases found in
small amounts in the
atmosphere
Group 1B-8B - Transition Metals
• Properties do not fit in
with those of any other
family
• Excellent conductors of
heat and electricity
• Most have high melting
points and are hard
• Much less active than the
alkali and alkaline earth
metals
• Can either be positively
or negatively charged
The Electrical Nature of Matter
Atom diagram:
Electrons ( - charge)
Protons
Neutrons
(+ charge)
(neutral charge)
Nucleus = center of atom
The nucleus is surrounded by
the electron cloud
The Electrical Nature of Matter
• Chemical bond is formed between two
atoms when the protons in one atom and
the electrons in another atom are attracted
together.
e-
• Example: Water
H
H
P+
oxygen
Ions and Ionic Compounds
• Compounds can either be made of molecules or
IONS
• Ion = charged atom
– Atom gains electrons = negative ion
• ANION
– Atom loses electrons = positive ion
• CATION
Compounds composed of ions = ionic compound
Ions and Ionic Compounds
• Writing Formulas for Ionic Compounds
1. Write the cation first, then the
anion.
2. The correct formula contains the
fewest + and – charges needed to
make the charge zero.
Criss-Cross Rule
Ions and Ionic Compounds
• Na = sodium atom
• Na+1 = sodium ION
• Cl = chlorine atom
• Cl-1 = chlorine ION
• Na+1Cl-1 = NaCl = table salt
Ions and Ionic Compounds
• Writing Ionic Formulas – Examples
– Calcium ion and Chlorine ion
• Ca+2 and Cl-1
• CaCl2 = “Calcium chloride”
– Aluminum ion and Carbonate ion
• Al+3 and CO3-2
• Al2(CO3)3 = “Aluminum carbonate”
Ions and Ionic Compounds
• Ionic compounds are neutral because the
positive and negative charges balance
each other.
• Ionic compounds are held together by the
attractive force between + and -
Ions and Ionic Compounds
When ionic compounds dissolve in water,
they separate into their ions and are called
AQUEOUS
NaCl (aq) = salt
water solution
Na+1
Cl-1
Cl-1
Na
+1
Ions and Ionic Compounds
• Polyatomic Ions – an ion consisting of a
group of bonded atoms
– See table of Common Ions
• Ex: NH4+ = ammonium ion
OH- = hydroxide ion
NH4OH = Ammonium hydroxide
Cations
• Elements or compunds
that like to lose electrons
so that their outermost
energy level is full (Octet
rule)
• They become positively
charged
• More protons (+) than
electrons (-)
• Groups 1A – 4A can lose
electrons
Anions
• Elements or compounds
that like to gain electrons
so that their outermost
energy level is full (Octet
rule)
• They become negatively
charged
• More electrons (-) than
protons (+)
• Groups 4A – 7A can gain
electrons
Ionic Bonding
+
= NaCl
• Sodium likes to lose one electron
• Chlorine likes to gain one electron
• Sodium “gives” its 1 electron to Chlorine and they bond
ionically
Na
+
Cl
=
Na Cl
Ionic Bonds
An ionic bond is the resulting attraction for an anion and
a cation after an electron is transferred from the
metal to the non-metal.
http://www1.icsd.k12.ny.us/chemzone/lessons/03bondin
g/mleebonding/ionic_bonds.htm
Covalent Bonds
A covalent bond exists when two electrons are shared
by two non-metallic atoms.
http://www1.icsd.k12.ny.us/chemzone/lessons/03bondi
ng/mleebonding/covalent_bonds.htm
Ions and Ionic Compounds
• It’s possible that one or more ionic
compounds could have been dissolved in
Riverwood’s water, causing the fish kill
• Complete the Water Testing Lab to test for
dissolved ions in solutions