Transcript Periodic Table and Bonding PPT Notes

ELEMENTS
Remember:
• Atoms of one type form an element
– A bunch of gold atoms form gold…etc.
• Elements are the simplest form of a
substance
• Every element is unique and has its own
chemical and physical properties
Compounds and Molecules
• A molecule is formed when two or more
atoms join together chemically.
• A compound is a molecule that contains
at least two different elements.
• All compounds are molecules but not all
molecules are compounds.
Atoms, Elements, Compounds,
Molecules
• O
S
CH4
Fe
N2
H
H 2O
H2SO4
O2
Elements are arranged:
Vertically into Groups
Horizontally Into Periods
Each atom has the
same number of
electrons in it’s
outermost shell.
Valence Electrons: Electrons in
the outer shell
• The number of outer or “valence” electrons
in an atom effects the way an atom joins
with other atoms.
• The way atoms join determine many
properties of the element.
• This is why elements within a group
usually have similar properties.
Each atom has the same number of
electron holding shells.
The numbers
represent the
period as well as
the amount of
electron holding
shells.
Each group has distinct properties
• The periodic Table is divided into several
groups based on the properties of different
atoms.
Noble Gases
Non-reactive
Gases at room
temperature
Very Stable
WHY STABLE?
Noble gases have full valence levels!
• Atoms whose shells are not full tend to
interact with other atoms and gain, lose,
or share electrons
Outermost electron shell (can hold 8 electrons)
Electron
HYDROGEN (H)
Atomic number = 1
First electron shell (can hold 2 electrons)
CARBON (C)
Atomic number = 6
NITROGEN (N)
Atomic number = 7
OXYGEN (O)
Atomic number = 8
Ionic bonds
• When atoms gain or lose electrons
• Charged atoms called ions are created
– Lose electrons---positive charge
– Gain electrons--- negative charge
–
– Like charges repel and opposite
charges
+
attract
Na
Cl
Na
Cl
Na
Sodium atom
Cl
Chlorine atom
Na+
Sodium ion
Cl–
Chloride ion
Sodium chloride (NaCl)
Ionic Bonds
• Electrons are transferred
• Forms between metals and
nonmetals
• Dissolve easily in water, usually
Covalent Bonds
• Sharing of outer electrons
• Very strong bond
• If “pull” is unequal creates a polar
covalent bond = a polar molecule
(ex: water)