- 1 - CHEMISTRY 2 REVIEW: MIDTERM Everything Energy Matter ...

CHEMISTRY 2 REVIEW: MIDTERM
PROPERTIES OF MATTER
• Everything is either energy or matter
• Matter is anything that has mass and occupies space (has a
measurable volume)
• A physical property of a substance is a characteristic that can be
observed and measured without changing the composition of the
substance.
• A chemical property describes the ability of a substance to
combine with or change into one or more other substances.
• The law of conservation of mass states that during a chemical reaction, mass is neither lost, nor gained.
à Mass of reactants = Mass of products
METALS METALLOIDS NON-METALS
Location on periodic table Left Along stair step line Right
Conductivity Good conductor Semi-conductor Poor conductor
Malleable/ductile Yes Depends on element No
Shiny Yes Depends on element No
Proportion of elements on periodic table Largest Smallest Small
ATOMIC STRUCTURE AND ELECTRONS IN THE ATOM
PROPERTIES OF SUBATOMIC PARTICLES
Particle Symbol Electrical
Charge
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Relative Mass
(in amu)
Location
Electron e- 1- 1/1840 Electron cloud
Proton p+ 1+ 1 Nucleus
Neutron n 0
• Information about an element
• Isotopes
o Atomic number identifies an element
0 1 Nucleus
o Atomic number is equal to the number of protons in the nucleus
o The number of electrons is equal to the number of protons which results in a net charge of zero
o Atomic number = Number of protons = Number of electrons
o All atoms of the same element have the same number of protons,
however they can have varying number of neutrons.
o Isotopes are atoms with the same number of protons but different
number of neutrons
o Isotopes are identified by their mass number
o Mass Number = Number of protons + Number of neutrons
Everything
Energy Matter
Element
Pure
Substance
Made of
Atoms
Compound
Mixture
Made of
Molecules

Bonding: Ionic vs. Molecular
• Valence electrons are the electrons in the highest occupied energy level of an atom.
• The number of valence electrons for a representative element is equal to the last number of its group
number. Example: phosphorus is in group 15 – it has 5 valence electrons.
• The octet rule: atoms tend to gain, lose or share electrons in order to have the electron configuration of
•
a noble gas
Chemical Names and Formulas
§ Ionic Compounds
o Commonly a metal + nonmetal
o Cation + anion
o Combine in a ratio so that the net charge is zero
o Use criss-cross method to write formula
§ Naming an ionic compound from a formula
o Name of cation + name of anion
o Example Al2O3 = aluminum oxide
§ Molecular Compounds
o Commonly two non-metals
o Name from formula for binary compound
§ Element 1: Prefix (if subscript > 1) +
name of element
§ Element 2: prefix + stem of name + -ide
§ Example: N2O5 = dinitrogen pentoxide
1 Mono 6 Hexa
2 Di 7 Hepta
3 Tri 8 Octa
4 Tetra 9 Nona
5 Penta 10 Deca
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CATIONS ANIONS
Form from metals Form from non-metals
Lose electrons Gain electrons
Positively charged Negatively charged
Charge = #electrons
lost
Type of
elements
IONIC
Charge = # electrons
lost
COMPOUNDS
MOLECULAR
COMPOUNDS
Metal + non-metal Non-metals only
Type of bond Ionic bond Covalent bond
Origin of
bonding
Smallest
particles
Transfer of
electrons
Sharing of
electrons
Ions Molecules

Chemical Reactions
§ Chemical equations are always written
o Reactants à products
o Multiple reactants or products are separated with “+” signs
§ Balancing equations
o Equations are balanced by using coefficients to show the relative amounts of each reactant and
product.
o NEVER change the formulas
o Make sure there are the same number of atoms of each type on both sides of the equation.
o This is because of the law of conservation of mass – matter is neither created or destroyed
TRENDS OF THE PERIODIC TABLE
• Atomic radius – size of atom: increases down a group, decreases across a period
Elements in same period have same
number of energy levels
Atomic radius decreases from left to
right across a period
Electromagnetic Spectrum
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Elements in same group have same
number of valence electrons
Atomic radius increases from top to
bottom in a group
From lowest to highest energy
1. Radio waves
2. Microwaves
3. Infrared
4. Visible light
5. Ultraviolet
6. X-rays
7. Gamma rays

Flame Test
• A flame test can be used to identify a METAL.
• An electron falling from an excited state will release energy in the
form of colored light.
• The color of the light depends upon the energy of the transition.
o Red – lowest energy
o Violet – highest energy
Counting Atoms
1. The symbol of an element represents 1 atom
Example: Na = 1 atom of sodium
2. A subscript indicates the number of atoms of a particular
element
Gas
Example: H2 = 2 atoms of hydrogen
3. A subscript outside of parentheses multiplies all elements
inside the parentheses
Example: Al(OH)3 = 1 aluminum, 3 oxygen, 3 hydrogen
4. A coefficient in front of a symbol indicates the number of
that element
Liquid
Example: 3 C = 3 atoms of carbon
5. A coefficient in front of a chemical formula indicates the number of molecules of that compound and
multiplies the number of atoms of each element in the formula
Example: 3 N2O4 = 3 molecules or 6 atoms of nitrogen, 12 atoms of oxygen
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Solid