Download Chemistry Review ATOMS

Chemistry Review
ATOMS
• Smallest unit of matter.
– Atoms make up everything (that has mass and takes up
space).
Protons (+)
• Determines the
identity of the Element
• Represents the Atomic #
• Positively charged
• Nucleus
• Part of the atoms mass
Neutrons – No charge
• Neutral – No charge
• Nucleus
• Part of the atoms mass
Electrons (-)
•
•
•
•
Negatively charged
smallest particles
Outside nucleus
Found in the electron
cloud
• Located in energy levels
Electric Charge of the Atom
• Overall charge of an atom is Neutral
• The # of (+) protons = the # of (–) electrons
– They cancel each other out
– Remember:
• Protons are positive
• Electrons are negative
• Neutrons are neutral (No charge) – They do not count
Atomic Particle Size
Nucleus
•
•
•
•
Center of the atom
Made up of Protons and Neutrons
Makes up the atoms MASS
Positively Charged!
Electron Cloud
• Area around the nucleus
where electrons are
found.
• Negatively Charged
Energy Levels
• Levels within the electron cloud that hold a
specific # of electrons.
– 1st level - 2 electrons
– 2nd level - up to 8 electrons
Valence Electrons
• Electrons on the outermost energy level of the
atom.
• Determine the atoms chemical properties,
including reactivity.
Atomic Number
• Top # on the periodic table
• # of protons in the atom
– Atomic # = 2
– 2 protons
Chemical Symbol
• 1 or 2 letter abbreviation for an element name
– 1st letter Capitalized
– 2nd letter – always lowercase
• Helium - He
Atomic Mass
•
•
•
•
Bottom #
Mass of the atom
Located in the nucleus
Protons + Neutrons
Determining the # of subatomic
particles in atoms
Use the following
A=P=E M–A=N
Atomic # = Protons = Electrons
Mass – Atomic # = Neutrons
Atom Models
ELEMENTS
• All the atoms that make up our universe
• Identified by the atomic # (# of protons)
Arrangement of the Periodic Table
Elements are arranged by:
1. By increasing Atomic # and mass
•
•
According to the # of protons the atom has.
Increases from left to right in each period (row)
2. By metals, non-metals and metalloids
•
According to their physical properties
3. By groups
•
According to their valence electrons and chemical
properties
– Reactivity – How they react chemically in chemical
reactions.
3 Main Types of Elements on the
Periodic Table
Metals
•
•
•
•
•
Make up most of the elements
All solid except Mercury
Has luster (shiny)
Good conductors of heat and electricity
Malleable – hammered or shaped into thin
sheets
• Ductile – stretched into wires
Nonmetals
• Usually gases or brittle solids
• Poor conductors of heat and electricity
– They are insulators
• Right side of the periodic table
• Only 17 nonmetals
Metalloids
• Called Semi-metals
• Share properties of both metals and nonmetals
• Located on the zig-zag line
between the metals
and nonmetals.
Groups/Families
• 18 Vertical Columns on
the periodic table
• Elements have the same #
of valence electrons
• Elements share similar
chemical properties
including reactivity
Periods
• 7 horizontal rows on the
periodic table
• Increase by atomic #
and mass
• Consist of elements
with the same number
of energy levels.
Chemical Compounds
• A compound is when 2 or more elements
chemically combine.
• The properties of a compound are often very
different from the elements themselves.
– Example: Water – H2O
• Compound with 2 hydrogen atoms and 1 oxygen atom
Chemical Formulas
• Formulas that use chemical symbols and
numbers to represent what makes up a
substance.
– NaCl – Sodium chloride (salt)
– Na – Sodium, Cl - Chlorine
– H2O – Dihydrogen monoxide (water)
– H – Hydrogen, O - Oxygen
– CO2 – Carbon dioxide
– C – Carbon, O - Oxygen
Subscripts
• Numbers written below and to the right of a
chemical symbol in a formula.
H2O – 2 Hydrogen, 1 Oxygen
• Tells how many atoms of an element are in
each molecule.
• Only used if more than one atom is present.
H2SO4
How many atoms of each element are in this
compound?
• H = Hydrogen – 2 atoms
• S = Sulfur – 1 atom
• O = Oxygen – 4 atoms
How many elements are there? How many total atoms?
• 3 elements
7 atoms
Coefficients
• # placed in front of a chemical symbol or
formula
• Identifies the # of molecules of a substance
– 2H2O = 2 molecules of H2O
– 3FeO3 = 3 molecules of FeO3
Coefficients X Subscripts
• To determine the number of atoms using
coefficients you multiply the coefficient with
the subscript.
• 2H2O - 2 molecules of H2O
= 4 Hydrogen atoms and 2 Oxygen atoms
2Fe2O3
• 2 Molecules of Fe2O3
=
• 2 X 2 = 4 Fe (iron) atoms
• 2 X 3 = 6 O (oxygen) atoms
Using Parentheses
• Multiply the subscript with each element in
parentheses.
• Al2(SO4)3
• Al = 2 atoms of Aluminum
• S = 3 X 1 = 3 atoms of Sulfur
• O = 4 X 3 = 12 atoms of Oxygen
Chemical Reactions
• Occurs when one or more substances change to produce one or
more different substances.
• Atoms are rearranged to form a totally new substance with
properties that are completely different
• Indicators of a chemical reaction
–
–
–
–
Gas formation
Solid formation – precipitate
Energy change – light, heat, or sound
Color change
Chemical Equations
• Uses chemical symbols and formulas to
represent a chemical reaction.
• 2H2 + O2 →
Reactants
Yield
Sign
2H2O
Products
Chemical Equations
• Reactants
– starting materials in a
chemical reaction.
• Products
– substances formed in
a chemical reaction.
Law of Conservation of Mass
• The mass of atoms and molecules is neither
created nor destroyed in chemical reactions.
– The # of atoms for each element in the reactants
must equal the # of atoms for each element in the
products in a chemical reaction.
– Chemical Equations must be balanced.
Chemical Equations Must Be
Balanced!
• Law of Conservation of Mass
• The # of atoms in the reactants must equal the
# of atoms in the products for each element
2H2 + O2 → 2H2O
• Is this equation balanced?
Reactants
H=
O=
→
4
2
Is this equation balanced?
Yes!
Products
H=4
O=2