Transcript Chapter 17- How Atoms Bond and Molecules Attract

CHAPTER 17HOW ATOMS
BOND AND
MOLECULES
ATTRACT
The Big Idea: Atoms and
molecules are sticky
17.1 ELECTRON-DOT STRUCTURES
Valence electrons=electrons in outermost shell
Electron- dot structures: a series of dots
surrounding an atomic symbol
Electron-dot structures help us
understand ionic and covalent bonds
Nonbonding pairs= electrons that are
relatively stable and are already in pairs
17.2 THE FORMATION OF IONS
Ion- an element w/ a net electric + or –
charge, caused by a loss(+) or gain(-) of
electrons
Atoms tend to gain/loose electrons to have a
filled outermost shell
The periodic
table tells us
the type of ion
each atom tends
to form.
17.3 IONIC BONDS
An ionic bond is the electric force of
attraction between two oppositely
charged ions.
Ionic compounds form when 2 ions
come together to create a compound.
-Ionic compounds have different
properties than the ions from which
they were made.
THE CHEMISTRY OF MINERALS
For all ionic compounds, positive and
negative charges must balance.
Ionic bonds usually form from elements
on opposite sides of the periodic table
Ex: Aluminum oxide. Al+3 + O-2= Al2O3
17.4 METALLIC BONDS
Metallic bond- when metal ions are held
together by freely flowing electrons.
-This accounts for metal’s ability to conduct
electricity and heat, as well as it’s ability to
be bent and shaped.
An alloy is a mixture or two or more metallic
elements
17.5 COVALENT BONDS
Covalent bonding is when atoms are held together by
a mutual attraction to the electrons they share.
Covalent compounds is when 2 or more
substances are held together by covalent
bonds. This forms a molecule.
-Chemists use a straight line to symbolize two
electrons involved in a covalent bond
# of covalent bonds an atom can form= # of
electrons needed to fill it’s outermost shell
17.6 POLAR COVALENT BONDS
Electronegativity- how strongly an atom can tug on
bonding electrons.
Dipole-separation of charge that occurs in a chemical
bond b/c differences in electronegativity of bonded
atoms
The greater an atom’s electronegatvivity, the
greater it’s ability to pull electrons towards
itself when bonded.
A nonpolar bond happens when no dipole
is formed because the two atoms have
relatively the same electronegativity
Polar bonds form when a very
electronegative atom and a weakly
electronegative atom are covalently bound.
-The further away elements are from each
other on the periodic table, the larger
difference they have in electronegativity.
17.7 MOLECULAR POLARITY
When dipoles go in the opposite
direction with equal strength,
they cancel out and the molecule
is nonpolar
17.8 MOLECULAR ATTRACTIONS
The strength of the strongest
attractions is still weaker than
chemical bonds
Ion-dipole: bond between an ion and polar
dipole molecule
Dipole-dipole: bond between 2 polar molecules.
-Ex of strong dipole-dipole: hydrogen bond.When H bonds to N,O, or F
-Reason why water had such high boiling point
Dipole-induced dipoles: temporary uneven
distribution of electrons