Download Section 4 Powerpoint review lecure

Chapter 4
Earth Chemistry
• Be sure to also review atomic
particles
• And the periodic table
Chapter 4:1
Matter
Objectives
• Compare chemical properties and physical
properties of matter
• Describe the basic structure of the atom
• Compare atomic number, mass number,
and atomic mass
• Define isotope
• Describe the arrangement of elements in
the periodic table
What is matter?
• Matter is anything that takes up space
and has mass.
• Amount of matter is the mass of an object
• Observable and measurable properties
All Matter has two major distinguishing properties
.
Matter
Physical Properties
Observed without changing
the composition of the substance
Density
Color
Chemical Properties
characteristics that describe how a
substance interacts with other substances
to produce different kinds of matter.
Iron rusting
Helium's unreactivity
Element
• A substance that cannot be broken down
into a simpler form by ordinary chemical
means.
Primary Earth Elements
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
All Others
Bohr_s_Model_of_the_Atom
Atom
• Is now defined as the smallest particle of an
element that retains the chemical properties of that
element. Made of subatomic particles
Electrons
-have a
negative
charge
Nucleus
Protons –
positive charge
and
Neutrons neutral charge
Electron Cloud
• Electrons do not orbit around the nucleus
like miniature planets… instead they are
found in “clouds” or regions of probability
Electrons
around the nucleus.
Atomic Number
• Each kind of atom has its own distinct atomic
number. Only atoms of that element have the
same atomic number.
• Atomic number equals number of protons
• Uncharged atom – equal number of protons and
electrons, atomic number = number of electrons
• For Example GOLD, has a atomic number of
79. Gold has 79 protons in its nucleus. No
atoms have an atomic number of 79 except
GOLD atoms.
Exploring_the_Modern_Periodic
_Table
Two_Rows_of_Elements_at_Bottom
_of_Periodic_Table
Periodic Table of Elements
Elements in same column have similar arrangement of electrons
Using_the_Modern_Periodic_Table
6
C
Carbon
12.011
[He]2s22p2
Atomic Number
Atomic Symbol
Atomic Name
Atomic Mass
Atomic Mass
• The mass number of any atom is the TOTAL
number of protons AND neutrons in the nucleus of
an atom.
• For example GOLD, has a mass number of 197 amu
or atomic mass units.
Isotopes
Atoms of the same element (the
same number of protons) with
different numbers of neutrons.
They have identical atomic numbers
but different mass numbers.
ISOTOPES
• Different number of neutrons / different masses yields
isotopes of same element with different properties
Average Atomic Mass
• Weighted average of
the atomic masses of
naturally occurring
isotopes of an element
• Average calculated for
Periodic Table
electron
neutron
proton
Valence Electrons
• Similarities in chemical
properties places
elements in periodic table
in columns or groups
• Outermost electrons in
cloud are Valence
• Atoms’ number of
valence electrons
generally same for every
atom in that group
Metals and Nonmetals
• Elements whose atoms
with only 1, 2, or 3
valence electrons lose
electrons easily
• Metallic properties and
classified as metals
• Elements whose atoms
ranging from 4-7 valence
electrons more likely to
gain electrons
• Classified as nonmetals
Families__Alkali_Metals__Halo
gens__Noble_Gases_
Section 4.2
Combinations of Atoms
Section Objectives
• Define compound and molecule.
• Interpret chemical formulas.
• Describe two ways that electrons form
chemical bonds between atoms.
• Explain the differences between compounds
and mixtures.
Elements_and_Compounds
Compound
• A substance that is
made of two or more
elements that are joined
by chemical bonds.
• The compound’s
properties differ from
those of the elements
that compose it.
Molecule
• The simplest unit of a compound that
retains all of the substances chemical
properties.
Diatomic Molecule
• Molecules made up of two atoms, which
can be the same element.
• N2, F2, Cl2, O2.
Chemical Formulas
How about (NH4)2CO3?
• A combination of
symbols and numbers
that show which
elements, and the
number of atoms of
each element, that make
up a molecule of a
compound. The
numbers here are called
subscripts.
Chemical Equations
• A formula that
describes the
chemical reaction
of elements and
compounds to form
new compounds.
Equation Structure
• reactants → products
• The arrow means
“gives” or “yields”.
• For the picture, the
chemical equation is:
2H2 + O2 → 2H2O
Balanced Equations
• The number of atoms of each type must be equal to
each other on either side of the arrow.
• You cannot change the chemical formulas.
• We put numbers (called coefficients) in front of the
reactants or products to make it balance.
So, Let’s Balance This Puppy!
CaCO3 + HCl → Ca2+ + Cl− + CO2 + H2O
CaCO3 + 2HCl → Ca2+ + 2Cl− + CO2 + H2O
Chemical Bonds
• The forces that hold atoms together in a
molecule.
• Produced by the sharing or transferring of
electrons from the outermost (valence)
electrons of two or more atoms.
Ions
• An atom or group of
atoms that carries an
electrical charge from
either gaining or losing
an electron(s), trying to
fill the valence shell
and “look” like a noble
gas.
• Gain = negative charge
Loss = positive charge
Ionic Bond
• The attractive force between oppositely
charged ions that result from the transfer of
electrons.
Ionic Compound
• A compound formed through the transfer of
electrons.
• MOST are formed by the transfer of electrons
from a metal to a non-metal.
• Example: NaCl (table salt)
Covalent Bond
• A bond based on
the attraction
between atoms that
SHARE electrons.
Covalent Compound
• A compound formed by the sharing of
electrons by two or more atoms. Each atom
“thinks” that it “looks” like a noble gas.
Diatomic Hydrogen
Polar Covalent Bonds
• Chemical bonds are rarely PURELY ionic
or covalent, they are usually somewhat “in
between”, and the atoms do not share the
electrons equally.
Metallic Bonds (Not In The Book)
Metals_and_Non_Metals
Heterogeneous Mixtures
• Where two or more
substances are not
uniformly distributed.
Granite, mostly a mixture
of orthoclase and quartz.
Homogenous Mixtures
• Means “having the same
composition and properties
throughout.”
• Also called a solution, in
which two or more
substances are uniformly
dispersed.
• Can be solid, liquid, or gas.
Smog build-up during the day
Alloy
• A solution composed
of two or more metals.
• For example, this 15th
century bronze door is
made up of a SOLID
solution of copper and
tin…BRONZE
Assignment
• 4.2 Key Terms
• Directed Reading