In 1789, French chemist Antoine Lavoisier grouped the known elements into categories he called metals, nonmetals, gases, and earths.
In 1789, what did French chemist Antoine Lavoisier do?
Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.
How did Mendeleev arrange the elements in his periodic table?
A periodic table is an arrangement of elements in columns, based on a set of properties that repeat from row to row.
What is a periodic table?
Mendeleev placed bromine in Group VII because bromine and chlorine have similar properties.
Why did Mendeleev place bromine in Group VII of his periodic table?
The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.
What evidence helped verify the usefulness of Mendeleev’s table?
Mendeleev arranged the elements in rows in order of increasing mass so that elements with similar properties were in the same column.
Describe how Mendeleev organized the elements into rows and columns in his periodic table.
The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.
How did the discovery of new elements such as gallium demonstrate the usefulness of Mendeleev’s table?
Mendeleev provided an organizing principle that worked for all of the known elements.
Scientists before Mendeleev had proposed ways to organize the elements. Why were Mendeleev’s efforts more successful?
In solitaire, cards are arranged into categories called suits and ordered by value.
What characteristic of solitaire did Mendeleev use as a model for his periodic table?
In order to place elements with similar properties in the same column, Mendeleev needed to leave spaces for undiscovered elements.
Why did Mendeleev leave space in his table?
The scientist test whether the model can be sued to make accurate predictions.
In general, how can a scientist test the correctness of a scientific model?
With only 17 known elements to work with, the scientist would not have had enough data
Inferring: Explain why it would not have been possible for a scientist in 1750 to develop a table like Mendeleev’s
Mendeleev based his predictions on the properties of nearby elements and other elements in the same column.
Predicting: How was Mendeleev able to predict the properties of elements that had not yet been discovered?
In the modern periodic table, elements are arranged by increasing atomic number (number of protons).
How is the modern periodic table organized?
Each row in the table of elements is a period.
What is a period?
The number of elements per period varies because the number of available orbitals increases from energy level to energy level.
Why does the number of elements per period vary?
Each column on the periodic table is called a group
What is a group?
Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.
Properties of elements repeat in a predictable way when what is being used to arrange elements into groups?
The pattern of repeating properties is the periodic law
What is periodic law?
Atomic mass is a value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes.
What does the atomic mass of an element depend on?
An atomic mass unit (amu) is defined as one twelfth the mass of a carbon-12 atom.
What is an atomic mass unit (amu)?
First, elements are classified as solids, liquids, or gases, based on their states at room temperature.
Second, elements are divided into those that occur naturally and those that do not.
The third classification system puts elements into categories based on their general properties.
Second, elements are divided into those that occur naturally and those that do not.
The third classification system puts elements into categories based on their general properties.
What three ways does the periodic table classify elements?
Elements are classified as metals, nonmetals, and metalloids.
What categories are used to classify elements on the periodic table?
Metals are elements that are good conductors of electric current and heat.
What are metals?
Transition metals are elements that form a bridge between the elements on the left and right sides of the table.
What are transition metals?
Nonmetals are elements that are poor conductors of heat and electric current.
What are nonmetals?
Metalloids are elements with properties that fall between those of metals and nonmetals.
What are metalloids?
Transition metals
Which type of metals tend to form compounds with distinctive colors?
Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.
How do properties vary across a period in the periodic table?
In the modern periodic table, elements are arranged by increasing atomic number.
What determines the order of the elements in the modern periodic table?
Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.
Describe the periodic law.
Atomic mass is a value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes.
What two factors determine the atomic mass of an element?
Metals, nonmetals, and metalloids
Name three categories that are used to classify the elements in the periodic table.
The elements become less metallic and more nonmetallic in their properties.
What major change occurs as you move from left to right across the periodic table?
The tellurium isotopes that are most abundant have many neutrons in their nuclei or that all tellurium atoms have more neutrons than iodine atoms.
Formulating Hypotheses: The atomic mass of iodine (I) is less than the atomic mass of tellurium (Te). But an iodine atom has one more proton than a tellurium atom. Explain how this situation is possible.
The atomic number of an element corresponds to the number of protons in the element’s atoms. The atomic number must be a whole number. All the places between 1 and 100 are already filled with existing elements.
Applying Concepts: Explain how you know that no new element with an atomic number less than 100 will be discovered.
Sodium reacts quickly and violently with water at room temperature. Magnesium will not react unless the water is hot.
Comparing and Contrasting: Compare the reactions with water of the elements sodium and magnesium.
A valence electron is an electron that is in the highest occupied energy level of an atom.
What is a valence electron?
Elements in a group have similar properties because they have the same number of valence electrons.
Why do the elements in a group have similar properties?
The elements in Group 1A are called alkali metals.
These metals have a single valence electron and are extremely reactive.
What are alkali metals?
The reactivity of alkali metals increase from the top of Group 1A to the bottom.
As you go from top to bottom of Group 1A how does the reactivity of alkali metals get affected?
An alkali metal has one valence electron.
How many valence electrons does an alkali metal have?
The elements in Group 2A are called alkaline earth metals.
All alkaline earth metals have two valence electrons. Metals in Group 2A are harder than metals in Group 1A.
What are alkaline earth metals?
Differences in reactivity among the alkaline earth metals are shown by the way they react with water.
How is the differences in reactivity among the alkaline earth metals shown?
Group 3A contains the metalloids boron, the well known metal aluminum, and three less familiar metals (gallium, indium and thallium). All these elements have three valence electrons.
The Boron Family
Aluminum is the most abundant metal in the Earth’s crust.
What is the most abundant metal in the Earth’s crust?
Group 4A contains a nonmetal (carbon), two metalloids (silicon and germanium), and two metals (tin and lead). Each of these elements has four valence electrons. Notice that the metallic nature of the elements increases from top to bottom within the group.
The Carbon Family
Except for water, most of the compounds in your body contain carbon.
Except for water, what element does most of the compounds in your body consist of?
Carbon
Which Group 3A element is a nonmetal?
Group 5A contains two nonmetals (nitrogen and phosphorus), two metalloids (arsenic and antimony), and one metal (bismuth). Despite their differences, all the elements in Group 5A have five valence electrons.
The Nitrogen Family
Besides nitrogen, fertilizers often contain phosphorus.
Besides nitrogen, fertilizers often contain what other element?
Group 6A has three nonmetals (oxygen, sulfur, and selenium), All the elements in Group 6A have six valence electrons.
The Oxygen Family
Oxygen is the most abundant element in the Earth’s crust.
What is the most abundant element in the Earth’s crust?
The elements in Group 7A are called halogens.
Each halogen has seven valence electrons. Despite their physical differences, the halogens have similar chemical properties.
What are Halogens?
The elements in Group 8A are called noble gasses.
Helium has two valence electrons. Each of the other gases has eight valence electrons. The noble gases are colorless and odorless and extremely unreactive.
What are noble gasses?
They have similar properties because they have the same number of valence electrons.
Explain why elements in a group have similar properties.
The reactivity of alkali metals increases from the top of Group 1A to the bottom.
What is the relationship between an alkali metal’s location in Group 1A and its reactivity?
Carbon
What element exists in almost every compound in your body?
Nitrogen and phosphorus
Which Group 5A elements are found in fertilizer?
The noble gases (Group 8A)
Which group of elements is the least reactive?
Hydrogen is placed with other elements that have a single valence electron.
Why is hydrogen located in a group with reactive metals?
The process that uses sunlight to produce sugar in plants
What biological function requires magnesium?
The energy needed to purify recycled aluminum is only about 5% of the energy needed to extract aluminum from bauxite.
Why is aluminum recycled?
To produce sulfuric acid
What is the main use of sulfur?
Chlorine is added to drinking water to kill bacteria
Why is chlorine added to drinking water?
The reactivity of nonmetals decreases from the top to the bottom of a group.
Making Generalizations: What happens to the reactivity of nonmetals within a group from the top of the group to the bottom?
c. mass
Mendeleev arranged the elements in his periodic table in order of
a. atomic number
b. number of electrons
c. mass
d. number of neutrons
a. atomic number
b. number of electrons
c. mass
d. number of neutrons
d. gallium
Mendeleev’s decision to leave gaps in his periodic table was supported by the discovery of
a. electrons
b. protons
c. argon
d. gallium
a. electrons
b. protons
c. argon
d. gallium
a. atomic number
In a modern periodic table, elements are arranged in order of
a. atomic number
b. number of isotopes
c. atomic mass
d. number of neutrons
a. atomic number
b. number of isotopes
c. atomic mass
d. number of neutrons
b. 7
How many periods does the periodic table have?
a. 18
b. 7
c. 9
d. 8
a. 18
b. 7
c. 9
d. 8
a. one twelfth the mass of a carbon-12 atoms
An atomic mass unit is
a. one twelfth the mass of a carbon-12 atoms
b. the mass of a carbon-12 atom
c. the mass of a neutron
d. the mass of a proton
a. one twelfth the mass of a carbon-12 atoms
b. the mass of a carbon-12 atom
c. the mass of a neutron
d. the mass of a proton
b. metal
An element that is shiny and conducts electric current is likely to be a
a. gas.
b. metal
c. metalloid
d. nonmetal
a. gas.
b. metal
c. metalloid
d. nonmetal
d. a transition metal
Copper is an example of
a. an alkali metal
b. an alkaline earth metal
c. a nonmetal
d. a transition metal
a. an alkali metal
b. an alkaline earth metal
c. a nonmetal
d. a transition metal
b. group
Elements that have the same number of valence electrons are
a. in the same period.
b. in the same group.
c. called noble gases.
d. called transition metals
a. in the same period.
b. in the same group.
c. called noble gases.
d. called transition metals
c. alkali metals
The most reactive metals are the
a. transition metals
b. alkaline earth metals
c. alkali metals
d. metalloids
a. transition metals
b. alkaline earth metals
c. alkali metals
d. metalloids
d. Group 8A
Which elements are all gases at room temperature?
a. Group 1A
b. Period 3
c. Group 7A
d. Group 8A
a. Group 1A
b. Period 3
c. Group 7A
d. Group 8A
Mendeleev knew their relative masses and properties.
What information did Mendeleev have about the elements he organized into a periodic table?
Mendeleev placed elements in the groups where they logically belonged based on their properties.
How did Mendeleev know where to leave the spaces in his table?
The number of elements per period varies because the number of available orbitals increases as the energy level increases.
Why does the number of elements vary from period to period?
An atomic mass is a weighted average of the atomic masses of an element’s isotopes. The distribution of the isotopes determines how much each isotope affects the weighted average.
Explain how the atomic mass of an element is affected by the distribution of its isotopes in nature.
Elements can be classified by their state at room temperature; by whether they exist in nature; and by whether they are metals, nonmetals, or metalloids.
List three ways that the elements in the periodic table can be classified.
Across a period from left to right, metals become less reactive and nonmetals become more reactive.
In general, what happens to the reactivity of elements in groups labeled A as atomic number increase across a period?
Elements in the same A group do not have identical properties because their valence electrons are in different energy levels
Why don’t the elements within an A group in the periodic table have identical properties?
The noble gases were difficult to discover because they are colorless, odorless, and vary rarely react.
Why was it difficult to discover the noble gases?
There is not enough data for the solid because solids at room temperature can be metals, nonmetals, or metalloids. There is enough data for the gas because there are no gaseous metals or metalloids at room temperature.
Classifying: If you know that an element is a solid at room temperature, do you have enough data to classify the element as a metal, metalloid, or nonmetal? if you know that the element is a gas at room temperature, do you have enough data? Explain your answers.
Boron, with an atomic mass of 10.81
Applying Concepts: An element on the periodic table has two naturally occurring isotopes. One isotope has an atomic mass of about 10 amu. The other isotope has an atomic mass of about 11 amu. What is the name of this element?
Three
Predicting: How many valence electrons would an element with atomic number 113 have?
Cesium is an extremely reactive metal; argon is an extremely unreactive nonmetal.
Applying Concepts: Why are samples of the alkali metal cesium usually stored in argon gas?
Halogens are always found in nature in compounds because halogens are highly reactive nonmetals.
Applying Concepts: Why are halogens found in nature only in compounds?
Silicon
Applying Concepts: Which element on the periodic table has chemical properties that are most similar to those of carbon?
You would choose fluorine because it is much more likely to reach than nitrogen is.
Designing Experiments: If you were trying to make a compound of the noble gas xenon, would you use nitrogen or fluorine? Explain your choice.
The beaker might shatter
Predicting: What might happen to a heated beaker made from glass that does not contain boron if the beaker were placed in a pan of ice water?
Nitrogen and phosphorus
Inferring: Based on the content of most fertilizers, name two elements other than carbon that are found in compounds in plants.
An element that is helpful in small quantities may be harmful when present in larger quantities. For example, trace amounts of selenium help maintain the immune system, but larger amounts can cause nerve damage.
Making Generalizations: Explain how the amount of a trace element an organism is exposed to affects the element’s ability to help or harm an organism. Use the example of selenium.
The books would not fall apart if stored in a noble-gas atmosphere.
Problem Solving: Sometimes old books fall apart when they are stored in air. Use what you know about the reactivity of elements to propose a way that old books could be kept from falling apart.
There is a repeating pattern of days and months on a calendar. However, Tuesdays do not necessarily have a different set of properties from Thursdays and there are no trends among Tuesdays equivalent to the trends in atomic mass or reactivity within a group in the periodic table.
Using Analogies: Explain how a calendar is similar to a periodic table and how it is different.
Magnesium is required to produce chlorophyll, the green pigment in plants.
Relating Cause and Effect: When corn plants have yellow leaves, it is a sign that the plants lack an essential element. Which element must be added to the soil to produce leaves with a healthy green color?
b) halogens
Which elements are as reactive as alkali metals?
a) alkaline earth metals
b) halogens
c) noble gases
d) transition metals
e) metalloids
a) alkaline earth metals
b) halogens
c) noble gases
d) transition metals
e) metalloids
c) 6
How many valence electrons do atoms of oxygen and sulfur have?
a) 2
b) 4
c) 6
d) 8
e) 10
a) 2
b) 4
c) 6
d) 8
e) 10
a) elements become less metallic
Moving across a period from left to right,
a) elements become less metallic
b) elements become more metallic
c) elements become more reactive
d) elements become less reactive
e) elements have fewer valence electrons.
a) elements become less metallic
b) elements become more metallic
c) elements become more reactive
d) elements become less reactive
e) elements have fewer valence electrons.
c) Nonmetals have properties opposite of those of metals
Which statement best describes nonmetals?
a) Nonmetals are good conductors of heat and electric current.
b) Nonmetals are brittle solids
c) Nonmetals have properties opposite to those of metals
d) Nonmetals are located on the left side of the periodic table
e) All nonmetals are extremely reactive
a) Nonmetals are good conductors of heat and electric current.
b) Nonmetals are brittle solids
c) Nonmetals have properties opposite to those of metals
d) Nonmetals are located on the left side of the periodic table
e) All nonmetals are extremely reactive
