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Ch. 2 and 6, the Periodic Table (Period A)
Ch. 4 and 5, The Atom (Period A)
Chapter 10 The Mole
Chapter 11 Chemical Reactions
Intro to Chemistry and Chemistry Measurement
Nomenclature Chp. 7, 8, 9 (period A)
section 1.2 pages 15-19
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Ch. 2 and 6, the Periodic Table (Period A)
Chapter 2: Matter and Change
Chapter 6: The Periodic Table
Editor: Nikki Steiner
Chapter 2 teaches about Matter and Change. This includes the properties of matter, the idea of mixtures, as well as elements and compounds, and also chemical reactions. Chapter 6 centers on The Periodic Table. It consists of lessons on how the elements are organized, how they are classified, and periodic trends in atomic size, ionization energy, ionic size, and electronegativity. Both chapters contain a wealth of information that further supplement our understanding of chemistry!
Chapter 2- Matter
Coeditor: Billy Arruda
Member: Andrea Vale
2.1 Properties of matter
Properties used to describe matter can be classified as
- property that depends on the amount of matter in a sample.
- property that depends on the type of matter in a sample.
the measure of the amount of space occupied by an object
- measure of the amount of matter an object contains
- Matter that has uniform and definite composition
Ex: Gold and Copper (also known as pure substances)
Every sample of a given substance has identical intensive properties because every sample has the same composition.
- a quality or a condition of a substance that can be measured or observed without changing the substance's composition.
Physical properties help scientists identify substances.
States of Matter
Three states of matter:
solid, liquid, gas.
Form of matter that has definite shape and volume.
Incompressible with tightly packed together particles.
Form of matter that has indefinite shape, flows, yet has a fixed volume.
volume of liquids don't change as the shape changes.
Form of matter that takes both the shape and volume of it's container.
easily compressible with widely spread our particles.
Gaseous state of a substance that is generally a liquid or solid at room temperature, as in water vapor.
There is a difference between vapor and gas. Gases are their own substances exist at room temperature, while vapors describe the gaseous state of a substance that is a liquid or solid.
The shape of samples change when it is melted, but the composition remains the same. Melting is an example of physical change.
When some properties of a material change, but the composition of a material does not change.
Physical changes include: boiling, freezing, melting, condensing, breaking,splitting, grinding, cutting, and crushing.
Physical changes can be classified as
reversible changes are changes that involve changing a substance from one state to another, like melting.
irreversible changes are changes that cannot be reversed, like breaking.
2.2 Classifying Mixtures
– physical blend of two or more components
Based on the distribution of their components, mixtures can be classified as heterogeneous or homogeneous
: a mixture in which the composition is not uniform throughout (Example: Chicken noodle soup – there is more chicken in one spoonful than in another)
: a mixture in which the composition is uniform throughout, also called a solution (Example: vinegar doesn’t look like a mixture. It’s a mixture of water and
, which dissolves in water.)
- Term used to describe any part of a sample with uniform composition and properties. A homogeneous mixture consists of a
, and a heterogeneous mixture consists of two or more phases (layers).
Differences in physical properties can be used to separate mixtures
: Process that separates a solid from the liquid in a heterogeneous mixture (Example: Draining pasta in a colander)
: When liquid is boiled to produce a vapor that is then condensed into a liquid
Distillating tap water: As water in the distillation flask is heated, water vapor forms, rises in the flask, and passes into a glass tube in the condenser. The tube is surrounded by cold water, which cools the vapor to a temperature at which it turns back into a liquid. The liquid water is collected in a second flask. The solid substances that were dissolved in the water remain in the distillation flask because their boiling pints are much higher than the boiling point of water.
Coeditor: Grant Casey
Member: Abby White
2.3 - Elements and Compounds
Distinguishing Elements and Compounds
is the simplest form of matter that has a unique set of properties
is a substance that contains two or more elements chemically combined in a fixed proportion
Example: Carbon, Oxygen, and Hydrogen are chemically combined to form
Compounds can be broken down into simpler substances by chemical means, but elements cannot
The physical methods used to separate mixtures, cannot be used to separate compounds
is a change that produces matter with a different composition than the original matter
Heating is one of the processes used to break down compounds into simpler substances
There is no chemical process that can break down an element into simpler substances
Heating will NOT cause water to break down, however electricity will
When electric currents pass through water, oxygen gas and hydrogen are produced
Properties of compounds are very different from those of elements
Distinguishing Substances and Mixtures
Determining by appearance is difficult
Characteristics to distinguish whether a mixture of a substance
If the composition of a material is fixed, the material is a substance
If the composition of a material may vary, the material is a mixture
Symbols and Formulas
use chemical symbols to represent elements, and chemical formulas to represent compounds
The symbols used today are based on a system that was developed by Jons JAcob Berzelius
He based his symbols upon latin names of the elements
Each element is represented by a one or two letter
The first letter is always capitalized, second is usually lowercase
If English and Latin name are similar, then the symbol is usually derived from the English name
Chemical symbols provide a short cut in writing the chemical formulas and compounds
Subscripts in chemical formulas are used to indicate the relative proportions of the elements in the compound
Because a compound has a fixed composition, the formula for a compound is always the same
2.4 - Chemical Reactions
When iron rusts, the compound iron oxide is formed (Fe2O3)
The ability of a substance to undergo a specific chemical change is called a
can only be observed when a substance undergoes a chemical change
burn, rot, rust, decompose, ferment, explode, corrode
usually signify chemical change
, matter never changes, but in a
matter always changes.
One or more substances change into one or more new substances during a
A substance present at the start of a reaction is called a
A substance produced in the reaction is called a
Recognizing Chemical Changes
Every chemical change involves a transfer of energy
Clues that help tell if there has been a chemical change:
a transfer of energy
change in color
production of a gas
formation of a precipitate
is a solid that forms and settles out of a liquid mixture
The only way to be sure a chemical change has occurred is to test the composition of a sample before and after the change.
Conservation of Mass
During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
Mass also holds constant during physical changes
When 10g of ice melts, 10g of water are produced.
Law of Conservation of Mass
states that that in any physical change or chemical reaction, mass is conserved.
Mass is neither created nor destroyed.
Easily seen when a reaction occurs in a closed container.
Chapter 6- The Periodic Table
Coeditor: Jordyn Renaghan
Member: Allison Fortier
Chapter 6.1 Organizing the Elements
Searching For an Organizing Principle
By 1700, only 13 elements had been identified
Chemists thought others existed
They assigned names for elements, but couldn’t isolate elements from their compound
Used scientific methods to search and succeeded in finding more
Was there a limit to the number of elements in existence?
Used properties of elements to sort/organize them
1829, JW Dobereiner published a classification system
Elements grouped in triads (may look different, but have similar chemical properties)
Triad = set of 3 elements with similar properties
One element in each triad usually had properties midway between the other 2
Not all known elements could be grouped in triads though
This is an example of a triad of elements (chlorine, bromine, iodine).
Mendeleev’s Periodic Table
Ideas for new systems arose between 1829 and 1869; none with wide acceptance
1869, Dmitri Mendeleev published a table of elements
Later, Lothar Meyer published an almost identical table
Mendeleev given more credit – published first and better explained the table’s usefulness
Needed a way to show relationships among more than 60 elements
Called a periodic table
Elements organized in groups based on sets of repeating properties
Organized in order of increasing atomic mass
this is an early representation of the table
left spaces in the table
knew bromine belonged with chlorine and iodine
predicted new elements would be discovered to fill spaces
predicted what their properties would be based on location in the tabl
as more elements were discovered, the predicted and real properties were very close
this convinced people that this table was very powerful
The Periodic Law
: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties
the number of protons is the atomic number
Henery Moseley-->1913, british physicist, determined an atomic number for each element
example: iodine, 53
In the modern periodic table, elements are arranged in order of increasing atomic number
the elements in the figure above are arranged by atomic mass
starting with hydrogen (1)
as you read left to right, the numbers increase
there are seven ROWS (left to right): period 1 has 2 elements; period 2 has 8 elements and so on
as the periods move from one to the next, there is a repeatative pattern similar in each period
this pattern is know as the periodic law (which is defined in the beginning of this section)
each period corresponds to a principal energy level
the elements in the COLUMNS (up and down) have similar properties
Coeditor: Kyle Gallagher
Member: Lauren O'Reilly
Metals, Nonmetals, and Metalloids
Most periodic tables are laid out like the one shown
Some elements from periods 6 and 7 re placed beneath the table (making the periodic table more compact and reflecting its underlying structure)
Each group in the table shown has three labels
Scientists in the U.S. used the labels in the red, while scientists in Europe used the labels in the blue (can cause confusion because different groups can be labeled the same number and letter)
The International Union of Pure and Applied Chemistry (IUPAC) proposed a new system for labeling groups in the periodic system to have a standard for all chemists to go by
Numbered groups from left to right 1 through 18 (black labels in the table shown)
The system used in the United States for labeling the groups will be more useful when studying how compounds form in chapters 7 and 8
Dividing elements into groups is not the only way to classify them based on their properties
Elements can be grouped into three broad classes based on their general properties
Across a period, the properties of elements become less metallic and more nonmetallic
Most elements are metals
They are good conductors of heat and electric current
A freshly cleaned or cut surface of a metal will have a high luster, or sheen
This is caused by the metal’s ability to reflect light
All metals are solids at room temperature (except for Mercury, Hg)
Many metals are ductile, meaning that they can be drawn into wires
Most metals are malleable, meaning that they can be hammered into thin sheets without breaking
Properties of metals can determine how those metals are used
• Iron (Fe) – The Gateway Arch in St. Louis Missouri, is covered in stainless steel containing iron and two other metals, chromium (Cr) and nickel (Ni). The steel is shiny, malleable, and strong and resists rusting. These are qualities that make it optimal for a large piece of art like this that is always out in the weather.
Copper (Cu) – Copper is ductile and second to only silver as a conductor of electric current. The copper used in electrical cables (due to its ability to conduct electricity) must be 99.99% pure.
Aluminum (Al) – Aluminum is one of the metals that can be shaped into a thin sheet, or foil. To qualify as a foil, a metal must be no thicker than about 0.15 mm, meaning that the aluminum’s malleability is crucial.
These are the elements at the upper-right hand corner of the Periodic Table
most nonmetals are gases at room temperature
includes main components of air: nitrogen and oxygen
some are solids
these are sulfur and phosphorus
one nonmetal bromine, is a dark-red liquid
variation among all the different nonmetals makes it harder to give identifying characteristics that apply to all nonmetals.
generally poor conductors of heat and electricity except
solid nonmetals are usually brittle, meaning easily shattered or broken
Bromine is a dark liquid nonmetal
Sulufur is one of the nonmetals that is not a gas, but instead a solid.
In the Periodic Table above, metalloids are the elements that are dark green.
Metalloids are the elements making a divider between the metals and the nonmetals
has similar properties to metal & nonmetals
under some conditions, it has metal-like properties, under others, it has nonmetal-like properties.
behavior and properties are determined by conditions
Silicon is a poor conductor of electricity
but, if Silicon is mixed with a little Boron, the mixture is now a good electrical conductor
Silicon can be cut to be made into computer chips
SIlicon by itself is a poor electrical conductor
Coeditor: Brynna Harum
Member: Maddie Myers
6.2 Classifying the Elements
Squares in the Periodic Table
e: table that displays the symbols and names of the elements, along with information about the structure of their atoms.
element name and atomic mass are below the symbol
vertical columns on the side are the # of electrons in each occupied energy level of a sodium atom
used to distinguish groups of elements
Group 1A elements=
Group 2a elements=
alkali earth metals
nonmetals of group 7A=
Electron Configurations in Groups
electrons play a key role in determining properties of elements
elements are separated into noble gases, representative elements, transition metals, or inner transition metals
Group 8A of periodic table
these nonmetals are often called inert gases because they rarely take part in a reaction
display a wide range of physical and chemical properties
metals, metalloids, and nonmetals
most are solids, few are gases at room temperature, bromine is the only liquid
s and p sublevels of the highest occupied energy level are not filled
its group number equals the number of electrons in the highest occupied energy level
Some of the representative elements exist in nature as elements!
- the compound chlorophyll
that absorbs light inside a leaf,
Arsenic- The earth's crust contains
ore that has a major souce of
arsenic and sulfur in it.
Sodium- When slat lakes evaporate,
they form salt pans.
The main salt in alt pans is sodium chloride.
In the periodic table, the B group separates the A groups on the left side of the table from the A groups on the right side
the transition metals are the B group
they provide a connection between the two sets of representative metals
displayed in main body of PT
classified based on their electron configurations
-the highest occupied s sublevel and a nearby d sublevel contain electrons-characterized by presence of electrons in d orbitals
inner transition metals
-the highest occupied s sublevel and a nearby f sublevel generally contain electrons-characterized by f orbitals that contain electronsBl
Blocks of elements
periodic table is divided into blocks, or sections, that correspond to the highest occupied sublevels
s block contains Groups 1A, 2A and helium
p block contains Groups 3A, 4A,5A, 6A, 7A, and 8A
d block contains transition metals
f block contains inner transition metals
each period on the periodic table corresponds to a prinicipal energy level
for transition elements, electrons are added to a d sublevel with a prinicipal energy level that is one less then the period number
for inner transition elements, the principle energy level of the f sublevel is two less then the period number
Using Energy Sublevels to Write Electron Configurations-Nitrogen
atomic number is equal to total number of electrons-for a representative element, the highest occupied energy level is the same as the number of the period where the element is located- from the group in which the element is located, you can tell how many electrons are in this energy level
nitrogen is located in the second period of the PT and in the third group of the p block-it has 7 electrons-the configuration of the two electrons in the first energy level is 1s^(2)- the configuration for the five electrons in the second energy level is 2s^(2)2p6^(3).
Coeditor: Catherine Murray
Member: Ryan McSweeney
Periodic Trends in Atomic Size
atomic size decreases across a period from left to right, and each element has one more proton and electron than the one before it
across a period, electrons are added to the same principal energy level
The increasing nuclear charge pulls the electrons in the highest occupied energy level closer to the nucleus and the atomic size decreases.
This video explains the periodic table:
is an atom or group of atoms with a positive or negative charge
-an atom is electrically neutral because it has the same number of protons and electrons
Positive and negative ions form when electrons are transferred between atoms.
Atoms of metallic elements tend to form ions by losing electrons from their highest occupied energy levels.
is an ion with a positive charge. A charge for a cation is written as the number with a plus sign.
Atoms of nonmetallic elements tend to form ions by gaining one or more electrons.
is an ion with a negative charge. The charge for an anoin is written as a number followed by a minus sign.
Coeditor: Ian Kelly
Member: Jordan Majka
Trends in Ionization Energy
Electrons can move to higher energy levels when atoms absorb energy.
Occasionally, there is enough energy to overcome attraction of protons in the nucleus of the atom.
The energy that is required to remove an electron from an atom is called it's
Ionization Energy is measured when the element is in it's gaseous state.
The removal energy of the first electron from the elements gaseous state is called an element's first ionization energy.
- On the periodic table, this first ionization energy tends to increase from left to right in a group and decrease from top to bottom.
In addition to first ionization energy, there are also second and third ionization energy which is subsequently the energy required to remove the second and third electron (if possible) from an element in it's gaseous state.
In these cases, second ionization energy is removing an ion from an atom with a "1+" charge (as one of it's electrons was removed in first ionization energy), and third ionization energy likewise is removing an ion from an atom with a "2+" charge, in turn creating a "3+" charge in the atom of the element in it's gaseous state.
Ionization energy is helpful in predicting what ions elements will form.
ex. group 1A Metals will tend to form ions with a 1+ charge as the energy between first and second ionization is huge.
heres a lecture on ionization energy
Group Trends in Ionization Energy
In general, first ionization energy decreases from top to bottom within an atomic group.
Because atomic size increases as atomic number increases. As an atom size increases, nuclear charge has a smaller effect on electrons in the highest occupied energy level.
Less energy required to remove electron ---------> Lower first ionization level.
Below is a figure that helps explain the idea better:
Periodic Trends in Ionization energy
Across a periodic table, first ionization energy tends to increase left to right
It also tends to increase bottom to top.
Below is another figure helping to explain the idea better:
Coeditor: Ally Luongo
Member: Brittany Morgan
Trends in Ionic Size
When metals and non-metals have a reaction; metal atoms lose electrons and non-metal atoms gain electrons
This transfer has an effect on the size of the ions that’ll form
Cations are always smaller than the atoms from which they form
Anions are always bigger than the atoms from which they form
A comparison for a metal is that the sodium ion radius is 95 pm, half of the sodium atom’s radius which is 191 pm
When a sodium atoms loses an electron , attraction between the remains increases making the radius smaller as they condense
Metals that are representative lose their outermost electrons during ionization.
Ion has one fewer occupied energy level
A comparison for an ion is that the radius of a fluoride ion is 133 pm while the radius of a fluoride atom is 62 pm; the opposite of the metal’s trend
In the periodic table there are two visible trends; (from left to right) a gradual decrease in the size of positive ions and the gradual decrease in the size of negative ions
Trends in Electronegativity
- the ability of an atom of an element to attreact electrons when the atom is in a compund
Scientists use factors such as ionization energy to calculate values for electronegativity
electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.
metals on the left of the periodic table have low values; nonmetals on the right of the periodic table have high values
electronegativity values among the transition metals are not as regular
the least electoneagtive element is cesium (electronegativity value of 0.7) and fluorine is the most electronegative element (electronegativity value of 4.0)
Summary of Trends
-trends for atomic size, ionization energy, ionic size, and electronegativity vary within groups and periods
- the trends that exist among these properties can be explaned by variations in atomic structure
-the increase in nuclear charge within groups and across periods explains many trends
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