3rd Quarter Review Guide
Topic 1: Elements and the Periodic Table
Essential Knowledge
All matter is made from about 100 different chemical elements. The Periodic Table of the Elements shows all of the known elements,
arranged by increasing atomic number. Each element has a symbol. The symbol for many of the elements is one capital letter. In two-letter
symbols for elements, the first letter is always an upper case letter, the second one a lower case.
The smallest particle of an element is an atom. Some common elements that are gases are composed of diatomic molecules containing two
atoms of the same element. Example: hydrogen H2(g) and oxygen O2(g).
Atoms are made of three types of subatomic particles: protons, neutrons and electrons. Each atom has a nucleus in the center, made of
protons and neutrons packed tightly together. An electron cloud surrounds the atomic nucleus.
The atomic number for an element is the same as the number of protons. All atoms of the same element have the same number of protons. A
proton has a positive charge and a relative mass of one.
The number of electrons is the same as the number of protons in a neutral atom. An electron has a negative charge and a relative mass of
zero.
A neutron has no charge and a relative mass of one.
There are only certain regions in the electron cloud where electrons are likely to be found. These regions are called energy levels. The lowest
energy level is closest to the nucleus; the highest energy level is farthest away from the nucleus. Electrons will occupy the lowest available energy
level(s) before they fill in higher levels.
The outermost electrons in an atom are called valence electrons. The period (row) number on the periodic table corresponds to the highest
energy level occupied by the valence electrons in an element.
Elements in the same group (column) on the periodic table have the same number of valence electrons. All of the group 1 elements have one
valence electron and group two elements have two. Group 13 elements have three valence electrons, group 14 elements have 4, group 15 have 5
and so on through group 18 elements, which have eight valence electrons.
An ion is an atom that has a charge because it has gained or lost electrons. Positive ions (cations) have lost electrons; negative ions (anions)
have gained electrons. The amount of charge is equal to the number of electrons lost or gained.
The principal energy levels (n) around the nucleus of an atom identify the specific regions (distances from the nucleus) where electrons are
likely to be found. Principal energy levels are identified by n=1, 2, 3 . . . with n=1 closest to the nucleus. As the value of n increases, so does the
distance from the nucleus.
Using the periodic table, the period (row) where an element is found indicates the number of occupied energy levels for that element. The
energy level of the valence electrons corresponds to the period number (row) where the element is found.
Each principal energy level is divided into sublevels (s,p,d and f). In a given energy level, the s sublevel holds up to 2 electrons, and always fills
before the p sublevel, which can hold up to 6 electrons.
Electron configurations indicate the filling order of all of the electrons in an atom. The coefficients represent the principal energy level, the
letters represent the sublevels and the superscripts represent the number of electrons in the sublevel.
Going down a group on the Periodic Table, each element has one more principal energy level filled with electrons than the element above it, so
the outer electrons are farther away from the nucleus. This means the size of the atoms increases going down a group. Therefore the atomic
radius increases going down a group.
Going from left to right across a period of the Periodic Table the valence electrons are all in the same principal energy level, but the number of
protons in the nucleus increases from one element to the next. This means that the nucleus becomes more positively charged and attracts the
electrons more strongly. Therefore, the atomic radius decreases going from left to right across a period.
Electronegativity is the ability of an atom in a bond to attract electrons. The electronegativity of an element can be judged from its position on
the periodic table.
The electronegativity increases across a period of the periodic table. (The atomic radius decreases, which means that the valence electrons
are held more tightly by the nucleus.).
The electronegativity decreases down a group (The valence electrons are further away from and more loosely held by the nucleus).
Topic 2: Compounds and Bonding
Essential Knowledge
Atoms of different elements can join together by chemical bonds to form a compound. A compound has totally different properties from its
elements.
3rd Quarter Review Guide
Chemical formulas show the ratio or number of atoms of each element in a compound. Example: 2 hydrogen atoms bonded to one oxygen
atom make a water molecule (H2O).
Subscripts in a chemical formula represent the relative number of each type of atom. The subscript always follows the symbol for the element.
The subscripts indicate the ratio elements (in terms of atoms or moles) in the compound.
Example: In a water molecule, H2O, there are 2 hydrogen atoms and 1 oxygen atom. This means that two moles of hydrogen combines with
exactly one mole of oxygen.
Parentheses are used when a subscript affects a group of atoms.
Example: the formula for magnesium nitrate is written Mg(NO3)2 to show that there is a ratio of one magnesium atom, 2 nitrogen atoms and 6
oxygen atoms in the compound.
Elements in groups 1,2 and 13 (metals) will lose electrons and form positive ions (cations).
Elements in groups 15, 16 and 17 (nonmetals) will gain electrons and form negative ions (anions).
Ionic compounds are formed by the attraction between positive and negative ions. The charges must be balanced, resulting in a compound with
no net charge.
When naming ionic compounds formed between group 1& 2 metals and group 15-17 nonmetals, the metal is written first followed by the
nonmetal with its ending changed to “ide” (Ex: MgO, magnesium oxide.)
An ionic bond is formed when a metal (element from group 1 through 13) transfers electrons to a non-metal (element from groups 15, 16 or
17). This is because metals form positive ions (lose electrons) and non-metals form negative ions (gain electrons), resulting in a strong
attraction between oppositely charged ions.
Formulas for ionic compounds are written by balancing the ion charges. When naming ionic compounds, the metal is written first followed by the
non-metal whose ending is changed to “ide”
Ex: Ca+2 + F-1  CaF2 Calcium flouride
Al+3 + O-2  Al2O3 Aluminum oxide
A covalent bond is formed when a non-metal shares electrons with another non-metal. Formulas for covalent molecules can be predicted from
the dot diagrams of the combining elements. When naming covalent compounds, the elements are given a prefix to indicate the number of that
element in the compound and the second element ends in “ide”.
Ex: NH3 Nitrogen trihydride
CO2 Carbon dioxide
Electron dot diagrams for elements show the number of valence electrons. Elements will transfer or share valence electrons in order to have
eight valence electrons (octet rule). Group 1&2 have one and two dots in their diagram, group 13 has three, group 14 has four, ending with group
18 with 8 dots in its electron dot diagram.
Electron dot diagrams for an element show the number of valence electrons for that element.
The Lewis dot diagram for a covalent compound shows how the atoms in a molecule share electrons to gain a filled valence level. A filled
valence level is called an octet. Lewis dot diagrams for most elements (except: Hydrogen) generally follow the octet rule. Each shared pair of
electrons in a Lewis diagram represents a single covalent bond.
A covalent molecule can also be represented by a structural formula in which each covalent bond is shown as a line joining two atoms. In other
words, a line in a structural formula represents two electrons ( a pair) shared by two elements.
A covalent bond consists of electrons shared between atoms. This sharing is not always equal, because different atoms have different
electronegativities. Unequal sharing results in a polar bond.
The more electronegative atom in a covalent bond will attract the electrons more strongly and this will result in it having a slight negative
charge. The less electronegative atom will therefore be slightly deficient in electrons and so will have a slight positive charge.
A covalent bond in which the atoms do not share their electrons equally and have slight electrical charges is known as a polar covalent
bond. (example: HF)
A covalent bond in which the atoms share their electrons equally and do not have slight electrical charges is known as a nonpolar covalent
bond (example: F2). Only two of the same atom can share electrons equally.
The shape of a molecule is determined by counting shared and unshared electron pairs in the molecule. Its shape and the polarity of its bonds
determine the polarity of a molecule.
A linear shape results from two atoms bonded together, or from three atoms bonded together with no unshared electron pairs on
the center atom. (N2 and CO2). This shape is nonpolar if the bonds are equivalent but polar if the bonds are different.
A tetrahedral shape results from four atoms bonded to a central atom and no unshared electron pairs (CH4). This shape is
nonpolar if the bonds are equivalent but polar if the bonds are different.
A pyramidal shape results three atoms bonded to a central atom and one unshared electron pair (NH3). This shape is always polar.
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A bent or angular shape results from two atoms bonded to a central atom and two unshared electron pairs. (H2O and H2S).
This shape is always polar.
A trigonal planar shape results from three atoms bonded to a central atom and no unshared electron pairs (BH3 and CH2O). This
shape is nonpolar if three of the same type of atoms is attached to the central atom, otherwise it is polar.
Polarity is determined by the distribution of electronegativity across the molecule. If the distribution is symmetrical (or even), then the
molecule is nonpolar. If the distribution is uneven (asymmetrical), then the molecule is polar.
Polar molecules have an uneven distribution of electronegativity that causes a dipole (a slight positive charge on one end and a slight
negative charge on the other end).
Topic 3: Kinetic Theory
Essential Knowledge
Atoms and molecules are in constant motion.
For a given substance, particles of a gas phase move fastest; particles in a liquid phase move slower and particles in a solid phase move slowest.
There is a direct relationship between temperature and speed of the particles. When the temperature increases, particles move faster.
Solids have a fixed shape. In a solid the particles are closely packed together. Each particle in a solid is held in one position and vibrates around that position.
This results in a definite shape and volume.
The particles in a liquid stay relatively close together, but they can move around each other (rotate or tumble). This results in a definite volume but no
definite shape.
Gas particles are far apart; they move rapidly and collide with each other and with the walls of the container. This random motion results in no definite shape or
volume.
Phase changes (changes in physical state) occur when particles either speed up or slow down changing their relative motions. For a given substance, freezing and
melting occur at the same temperature. Boiling and condensing also occur at the same temperature. For example, water both freezes and melts at 0oC (and both
boils and condenses at 100oC). Which phase change takes place depends on whether heat (energy) is being added or removed.
Phase changes that require heat (like melting or boiling) are endothermic.
ΔH is positive for an endothermic change. This means heat goes in.
Phase changes that give off heat (like freezing and condensing) are exothermic.
ΔH is negative for an exothermic change. This means heat is released.
The amount of heat needed to melt a specific amount of a solid is called the heat of fusion.
The amount of heat needed to boil a specific amount of a liquid is called the heat of vaporization.
To calculate the total heat required to complete a phase change multiply the heat of fusion,
 Hf, times the total mass when melting. For boiling, multiply the heat of vaporization,  Hv.
Melting:
Boiling:
Heat = mass x  Hf
Heat = mass x  Hv
Elements form bonds to become more stable. A filled valence configuration (eight s and p electrons) is very stable. This is why noble gases (group 18) are
stable and do not react. When elements react to form compounds they exchange or share the correct number of electrons to reach this stable state.
Potential energy is stored energy. Chemical bonds contain potential energy.
Energy is required to break bonds. Breaking bonds is endothermic (requires energy). Energy is released when bonds are formed. Forming bonds is exothermic
(energy is released).
Chemical reactions are either endothermic or exothermic depending on whether the total energy needed to break the old bonds or the energy released when
forming the new bonds is greater.
In chemical reactions bonds are broken and new bonds are formed. The energy absorbed in breaking the bonds is never exactly equal to the energy released
when the new bonds are formed. Therefore, all reactions are accompanied by a change in potential energy that can be measured and is represented by the
symbol  H.
An energy level diagram can also be used to represent the energy change during a chemical reaction.
3rd Quarter Review Guide
Products
Reactants
H
Products
H
Reactants
Endothermic
Exothermic
For Exothermic reactions (H), the energy required to break the bonds of the reactants is less than the energy released in making the bonds of the
products.
For Endothermic reactions (+H), the energy required to break the bonds of the reactants is greater than the energy released in making the bonds of the
products.
The Heat of Reaction is the net amount of energy released or absorbed (∆ H) in a chemical reaction can be calculated from the balanced equation. The value for
∆ H is given in kilojoules (kJ).
H = HProd – HReact
Exothermic reactions, H (–) and the HReact > HProd
Endothermic reactions, H (+) and the HProd > HReact
Temperature is the measure of the average kinetic energy (movement) of the gas particles. This must be expressed in Kelvin (K) for all Gas Law calculations.
273K = 0o C (K=oC + 273)
Pressure and temperature both affect the volume that a gas occupies.

Pressure and volume are inversely related; if pressure increases, volume decreases.

Temperature and volume are directly related; if temperature increases, volume increases.
Topic 4: The Mole and Stoichiometry
Essential Knowledge
Atoms and molecules are too small to count. Mole is the unit used to tell how many particles are in a certain amount of a
substance. A mole is 602,000,000,000,000,000,000,000 particles (atoms or molecules). Expressed in scientific notation, a mole is
6.02 x 1023 particles.
Scientific notation is used to express very small or very large measurements in powers of ten. It expresses quantities by using a
number between one and ten, which is then multiplied by ten to a power to give the quantity its proper magnitude.
The sum of the protons and neutrons in an atom is known as the mass number.
Isotopes are atoms of the same element that have different numbers of neutrons. Some isotopes are radioactive, many are not.
An element’s atomic mass is a weighted average of the masses of all the known isotopes of the element.
The mass of one mole of any element is the same as the element’s atomic mass in grams (called molar mass).
The molar mass of a compound is the sum of the molar masses of the individual elements that make up the compound.
The percent by mass of an element in a compound can be determined:
% by mass of element = total mass of element in compound X 100
total mass of the compound
Molar masses from the periodic table can be used to calculate the number of moles in a given mass of an element or compound.
This is because the masses on the periodic table represent the number of grams in one mole.
Because matter cannot be created or destroyed, the total mass of the products is equal to the total mass of the reactants
in a chemical reaction.
Molar masses from the periodic table and mole ratios from the balanced equation can be used to calculate the mass of a reactant or
product.
The molar coefficients from balanced chemical equations are used to predict the masses of reactants or products.
At STP (standard temperature and pressure, 0o Celsius and 1 atmosphere) the volume of 1 mole of any gas is 22.4 liters.
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The number of moles of a gas (n) can be detaermined if the pressure (P), temperature (T), and volume (V) of the gas sample are
known, using the constant R according to the following equation:
PV = nRT
Topic 5: Chemical Reactions
Essential Knowledge
Chemical reactions occur when atoms interact and rearrange to form new substances. The reacting substances have different properties from
the substances produced.
In a physical change, the physical properties of a substance change, but the identity of the substance does not change. Steam, liquid water and
ice have different physical properties, but they are all the same substance, H2O.
Physical properties such as mass, volume and density are used to describe a substance.
The chemical reaction where elements react (bond together) to form a compound is called synthesis. Example: Hydrogen gas and oxygen gas
react to synthesize water. 2H2 + O2  2H2O
The elements in a compound can only be separated by a chemical reaction. This reaction breaks the bonds between the elements resulting in
decomposition. (Example: water decomposes to form hydrogen and oxygen gas.
2H2O  2H2 + O2
In both reactions, the rearrangement of atoms results in chemical bonds being broken and formed.
Bond breaking requires energy while bond making releases energy
A chemical equation is a record of what happens in a chemical reaction. It shows the formulas of all the reactants on the left hand side of the
arrow, and the formulas for all the products on the right hand side.
A balanced chemical equation has the same number of atoms of each element on either side of the arrow. When balanced, the coefficients
show the number of moles (mole ratio) of each substance that are required for a complete reaction.
Because matter cannot be created or destroyed, elements must be conserved in a chemical reaction. There must be the same number of each
kind of atom on both sides of a balanced equation. The only way to balance a chemical equation is by placing coefficients in front of each
substance until each side has the same number of atoms of each element.
When two or more substances combine to form a single product, the reaction is called a synthesis reaction. For example, the
formation of water from hydrogen and oxygen gases is a synthesis reaction:
2H2 (g) + O2 (g)  2H2O (l)
synthesis
In a decomposition reaction, a compound breaks down into two or more simpler substances. For example, in electrolysis, water is
broken down into hydrogen and oxygen gases:
2H2O (l)  2H2 (g) + O2 (g)
decomposition
Decomposition and synthesis are opposite chemical processes.
In a single replacement reaction one element takes the place of another in a compound. The general form for a single replacement reaction is
A + BX  AX + B
Where A and B are elements and BX and AX are ionic compounds.
An example is: Cu + FeCl2  CuCl2 + Fe.
In a double replacement reaction the positive portions of two ionic compounds are interchanged. The general form for a double replacement
reaction is
AX + CY  AY + CX
Where the cations A and C in two ionic compounds that swap partners.
An example is: BaCl2 + Na2O  BaO + 2NaCl
Predict products of single and double replacement reactions.
Copper(II) nitrate + zinc  _________ + __________
Silver nitrate + ammonium sulfate  _________ + ________
Cu(NO3)2(aq) + Zn(s)  _________ + __________*
AgNO3 + (NH4)2SO4  _________ + __________*
3rd Quarter Review Guide
*Note that nitrate (NO3)1- is a polyatomic ion that acts as a single particle with a single charge. Also, know the charges for the sulfate (SO4 )2ion, ammonium ion (NH4 )1+, hydroxide ion (OH )1-, carbonate ion (CO3 )2-, and the phosphate ion (PO4 )3-.
Combustion reactions are exothermic reactions in which oxygen combines with other elements producing carbon dioxide and water.
One example is the reaction between methane and oxygen in a Bunsen burner:
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) + energy
Topic 6: Solutions
Essential Knowledge
If a substance contains different types of particles, then it is called a mixture. (Example: Soapy water is a mixture of many water molecules and a
few soap particles.)
In a heterogeneous mixture, the different parts can be easily seen (like salt and pepper mixed together).
In a homogeneous mixture the particles are mixed so well that the separate parts cannot be seen (like salt dissolved in water.)
A solution is a homogeneous mixture because the separate parts of the mixture cannot be seen. The solvent (usually water) is the part of
the solution that is present in largest amount. The solute is the substance that is dissolved.
A saturated solution has all the dissolved solute that it can hold, and can be identified by undissolved solute particles on the bottom after mixing.
An unsaturated solution can still hold more solute.
Solubility is defined as the amount of solute that will dissolve in 100 g of solvent.
Dissolving is a physical change that involves heat. Dissolving and dissociation can be represented by an equation.
Example: NaCl(s) + heat  Na+(aq) + Cl-(aq) ΔH is positive
If a solution gets colder when a solute dissolves, it is an endothermic change and ΔH is positive, and heat is written to the left of the arrow.
If a solution gets warmer when a solute dissolves, it is an exothermic change and ΔH is negative, and heat is written to the right of the arrow.
Solutions that contain ions are called electrolytes because they can conduct an electric current. Therefore, solutions of ionic compounds in water
(aqueous solutions) are electrolytes, because ionic compounds dissociate as they dissolve. Conductivity is directly related to the number of ions
in the solution.
Solutions that do not contain ions are called non-electrolytes because they cannot conduct an electric current.
The concentration of a solution is the amount of solute contained in a certain volume of solution. If a solution contains a small amount of solute it
is called dilute, and if it contains a large amount of solute it is called concentrated.
In chemistry, concentration is given as molarity, the number of moles of the solute in one liter of solution and expressed as moles/liter or
just M.
The general rule for predicting solubility is like dissolves like. Water is a polar substance, so it can dissolve ionic and polar solutes. Oil is nonpolar, so oil will not dissolve in water. Oil and water don’t mix but different oils do because a non-polar solute will dissolve in a non-polar solvent.
An aqueous (aq) solution is a homogeneous mixture of a solute (or a mixture of solutes) in water (the solvent). Like other mixtures it can be
separated by a physical separation such as distillation or chromatography. One way to express the concentration of a solution is called molarity
(M = moles/L).
Solubility is the amount of solute that will dissolve in 100 g of solvent. Polar substances are soluble in other polar substances, and non-polar
substances are soluble in other non-polar substances.
Dissociation is the physical separation (dissolving) of ions from a compound. Any substance that dissociates is capable of being an electrolyte.
.
Topic 7: Experimentation
Essential Knowledge
Know the proper use of laboratory safety equipment and the laboratory safety rules and procedures that are described in your Safety
Contract. (goggles, aprons, gloves, safety shower, eyewash, broken glass container, fume hood and fire blanket)
The independent variable (IV) in an experiment is the variable that the experimenter changes. The dependent variable (DV) is the variable
that responds to the changes. For example: What is the effect of temperature (the IV) on how many drops of water (the DV) fit on a penny?
Determine the mean (average) of a set of volume (mL) or mass (g) measurements using the rules for significant digits.
3rd Quarter Review Guide
A research question asks about the relationship being investigated. A hypothesis predicts the answer to a research question based on prior
observation. An explanation of a hypothesis justifies the prediction using quantified observations and theoretical background.
Identify equipment: ring stand, funnel, watch glass, beaker, graduated cylinder and evaporating dish.
Demonstrate filtration and evaporation and explain when each can be used to physically separate a mixture. Define filtrate as the liquid that
passes through the filter.
Measure volume of a liquid in milliliters (mL) using a graduated cylinder and stating measured digits plus the estimated digit.
Measure mass in grams (g) using an electronic balance and identifying the estimated digit.
Describe and demonstrate safe techniques for lighting and using gas burners.
Understand and use Material Safety Data Sheet (MSDS) warnings including: handling chemicals, lethal dose (LD) hazards, disposal and chemical
spill clean-up.
Given a graph of experimental data, identify the independent variable (IV) and the dependent variable (DV) and interpret the relationship
between the variables.
A pipette is used to add the final amount of solvent to a volumetric flask to ensure a precise concentration of a solution.
Mixtures can be separated based on the physical properties of the components of the mixture.

Centrifugation (using a centrifuge) separates mixtures by density.
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Distillation separates mixtures by boiling point
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Filtration separates mixtures by particle size.
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Chromatography separates mixtures based on attractive forces between particles.
An experimental design consists of the research question, a hypothesis, the independent and dependent variables, control and constants, data
and observations, data analysis and conclusion.
Volume units include: 1 L =1 dm3 = 1000 cm3 = 1000 mL
Energy is measured in Joules. 1000 J= 1 kJ
Pressure units include: 1 atm = 101 kPa = 760 mmHg
Temperature measures average kinetic energy of particles.