Download Chapter 2 - Intro to Chemistry

Introduction to
Chemistry
Properties of Matter
 Matter - anything that has mass and volume
mass - quantity of matter in an object
volume - amount of space matter takes up
 Physical properties
 Characteristics of matter that can be observed and
measured without permanently changing the
identity of the matter
 Chemical properties
 The ability to change into another new substance
as a result of a chemical change
Identify the Change
Physical
Breaking
Rusting
Burning
Bending
Freezing
Fermenting
Melting
Boiling
Exploding
Chemical
X
X
X
X
X
X
X
X
X
Phases of Matter
 Phase change (solid  liquid  gas)
 Chemical composition of substance is not
altered
 H 20
 Solid phase - ice
 Liquid phase - water
 Gas phase - water vapor
The Atom
 Atom
 Basic unit of matter
 Incredibly small
 Contains subatomic
particles
 Protons
 Neutrons
 Electrons
The Nucleus
 Center of the atom
 99.9% of all the atom’s mass is located here
 Contains neutrons and protons
 Proton – positively charged particle
 Neutron – neutral (no charge) particle
 Proton and neutron are nearly equal in mass (1 amu)
Electrons
 Energy levels found outside the nucleus
 Electrons - negatively charged subatomic particle
 Found outside of the nucleus traveling in different
energy levels
 Mass is almost 200 times less than a proton or neutron
(1/1836 amu)
Atomic Structure
Under normal conditions:
 # protons = # electrons
 atom has a neutral charge
Atomic Number and Mass Number
 Atomic number
 number of protons
in the nucleus of an
atom
 number of protons
identifies an atom
 atoms of the same
substance have the
same atomic
number
 Mass number
 total number of
protons and
neutrons in the
nucleus of an
atom
Atomic Number Example
Q: If a Carbon atom has 6 protons and 6
neutrons in the nucleus, what is its
atomic number?
Atomic Number Example
Q: If a Carbon atom has 6 protons and 6
neutrons in the nucleus, what is its
atomic number?
A: Its atomic number is 6 (since it has 6
protons)
Mass Number Example
Q: If a Carbon atom has 6 protons and 6
neutrons in the nucleus, what is its mass
number?
Mass Number Example
Q: If a Carbon atom has 6 protons and 6
neutrons in the nucleus, what is its mass
number?
A: Its mass number is 12 (6 protons + 6
neutrons)
Think About It
Q: If an atom has 8 protons in its nucleus,
how many electrons must it have?
Think About It
Q: If an atom has 8 protons in its nucleus,
how many electrons must it have?
A: 8 electrons
Think About It
Q: If an atom has 8 protons in its nucleus,
how many neutrons must it have?
Think About It
Q: If an atom has 8 protons in its nucleus,
how many neutrons must it have?
A: You cannot tell
Think About It
Q: If I now tell you that the mass number
of the atom is 16 (and there are still 8
protons), now can you tell the number of
neutrons?
Think About It
Q: If I now tell you that the mass number
of the atom is 16 (and there are still 8
protons), now can you tell the number of
neutrons?
A: 8 neutrons
Think About It
Q: An atom has 11 electrons and a mass
number of 23, how many neutrons does it
have? What is its atomic number?
Think About It
Q: An atom has 11 electrons and a mass
number of 23, how many neutrons does it
have? What is its atomic number?
A: 12 neutrons and atomic # of 11
Chemical Elements
 Element
 Substances that
consist entirely of
one type of atom
 112 known elements
 90 elements found in
nature (22 are “manmade”)
 Each represented by
a chemical symbol
Chemical Symbols
 Sulfer (S) & Potassium (K) are solids
 Oxygen (O) & Nitrogen (N) are gases
 Mercury (M) & Bromine (Br) are liquids
 Why do you think the symbol for lead is Pb?
 Why do you think the symbol for gold is Au?
Chemical Symbols
 Sulfer (S) & Potassium (K) are solids
 Oxygen (O) & Nitrogen (N) are gases
 Mercury (M) & Bromine (Br) are liquids
 Why do you think the symbol for lead is Pb?
(Pb stands for plumbus)
 Why do you think the symbol for gold is Au?
(Au stands for aurum)
Isotopes
 Isotopes
 Atoms of the same element that have the
same number of protons, but different
numbers of neutrons
 Represented by using the mass number of
an isotope to the atomic symbol
Isotope Example – Helium
Radioactive Isotopes
 Atoms that emit radiation (their nuclei are unstable and
break down)
 Many elements have at least one radioactive isotope
 All isotopes above atomic number 83 are radioactive
 Uses include: studying living organisms, diagnosing and
treating disease, sterilizing foods, and measuring the ages
of rocks
Chemical Compounds
 Produced when two or more elements
combine to form substances consisting of
two or more different atoms
 Involves the combination of two or more
different atoms in definite proportions
Chemical Compounds
 H20 - 2 atoms of hydrogen and 1 atom of
oxygen
Oxygen
H
H
 What elements are present in H2SO4?
Chemical Compounds
 H20 - 2 atoms of hydrogen and 1 atom of
oxygen
Oxygen
H
H
 What elements are present in H2SO4?
 2 atoms of Hydrogen
 1 atom of Sulfur
 4 atoms of Oxygen
Interactions of Matter
 Objectives
 Explain how electron arrangement
determines an atom’s reactivity
 Describe two types of chemical bonds
 Thinking Skill
 Demonstrate an understanding of
knowledge
Chemical Bonding
 Compounds are formed by the interactions of
individual atoms
 The location of electrons determines the
types of bonds an atom will form
Chemical Bonding
 Energy levels can only hold a certain number
of electrons
 1st energy level = 2 electrons
 2nd energy level = 8 electrons
 3rd energy level = 8 electrons
 When the outermost energy level has the
maximum number of electrons it is very stable
 The outermost energy level wants 8 electrons - it will gain,
lose, or share electrons to gain this stability
Ionic Bonds
 Bond that involves a TRANSFER of
electrons from one atom to another
 Often occur between a metal and a
nonmetal
 Ion
 Charged particle
 Formed when an ionic bond occurs
Ionic Bonding - NaCl
Covalent Bonds
 Bond that involves
the sharing of
electrons
 Bonds can be
single, double, or
triple
 Forms a molecule
Chemical Reactions (3-4)
 Objectives
 Identify the substances involved in a
chemical reaction
 Describe the role of energy in chemical
reactions
 Thinking Skill
 Demonstrate an understanding of
knowledge
 Chemical Reaction: any process in which a
chemical change occurs
 Reactants
 Elements or compounds that enter into a chemical reaction
 Products
 Elements or compounds produced by a chemical reaction
 Chemical equation
 Symbols and formulas are used to represent reactants
and products
 Chemical Reaction: any process in which a
chemical change occurs
 Reactants
 Elements or compounds that enter into a chemical reaction
 Products
 Elements or compounds produced by a chemical reaction
 Chemical equation
 Symbols and formulas are used to represent reactants
and products
Reactants
Products
Chemical Reactions
 Exothermic Chemical Reactions
 Reactions that release energy occur spontaneously
 Endothermic Reactions
 Reactions that absorb energy