Chemistry Chapter: Periodic Table and Elements

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Questions and Answers

How are elements in the periodic table arranged?

The elements in the periodic table are arranged in order of atomic (proton) number and so that elements with similar properties are in columns, known as groups.

Why is this table called a periodic table?

The table is called a periodic table because similar properties occur at regular intervals.

What similarities do elements in the same group have?

Elements in the same group in the periodic table have the same number of electrons in their outer shell, giving them similar chemical properties.

Before the discovery of protons, neutrons and electrons, how did scientists classify elements?

Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights. Signup and view all the answers

What was the problem of the early periodic tables?

The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed. Signup and view all the answers

How did Dimitri Mendeleev overcome problems?

Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights. Signup and view all the answers

What did Mendeleev do when the elements were discovered?

Elements with properties predicted by Mendeleev were discovered and filled the gaps. Signup and view all the answers

What did the knowledge of isotopes make possible?

Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct. Signup and view all the answers

What are metals?

Elements that react to form positive ions are metals. Signup and view all the answers

What are non-metals?

Elements that do not form positive ions are non-metals. Signup and view all the answers

Where are metals found on the periodic table?

Metals are found to the left and towards the bottom of the periodic table. Signup and view all the answers

Where are non-metals found on the periodic table?

Non-metals are found towards the right and top of the periodic table. Signup and view all the answers

What are the properties of metals?

Metals are strong but malleable, good conductors of heat and electricity, have high boiling points and melting points, and exhibit metallic bonding. Signup and view all the answers

What are the properties of non-metals?

Non-metals do not have metallic bonding, are dull-looking, brittle, aren't always solid at room temperature, do not conduct electricity, and often have lower density. Signup and view all the answers

Why are Group 0 elements called noble gases?

Group 0 elements are called noble gases because they are unreactive and do not easily form molecules due to their stable arrangements of electrons. Signup and view all the answers

What is the arrangement of Group 0 elements?

The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons. Signup and view all the answers

What are the properties of Group 0 elements?

Group 0 elements exist as monatomic gases, are colorless at room temperature, are inert, and have boiling points that increase with atomic mass. Signup and view all the answers

What are Group 1 metals also known as?

The elements in Group 1 of the periodic table are known as the alkali metals. Signup and view all the answers

What are the properties of Group 1 metals?

Lithium, sodium, potassium, rubidium, caesium, and francium are soft and have low densities. Signup and view all the answers

What is the trend of Group 1 metals?

In Group 1, the reactivity of the elements increases going down the group, along with lower melting and boiling points and high relative atomic mass. Signup and view all the answers

How do alkali metals form ionic compounds with non-metals?

It's easy for Group 1 elements to lose their outer electron, so they react to form ionic compounds that are white and dissolve in water to form colorless solutions. Signup and view all the answers

What happens when alkali metals (Group 1) react with water?

They react vigorously to produce hydrogen gas and metal hydroxides, with more reactive alkali metals producing violent reactions. Signup and view all the answers

What happens when alkali metals (Group 1) react with chlorine?

They react vigorously when chlorine gas is heated to form white metal chloride salts, with increasing reactivity down the group. Signup and view all the answers

What happens when alkali metals (Group 1) react with oxygen?

Group 1 metals can react with oxygen to form a metal oxide, with different products depending on the metal involved. Signup and view all the answers

What are Group 7 elements known as?

The elements in Group 7 of the periodic table are known as the halogens. Signup and view all the answers

What is the trend in Group 7?

In Group 7, the further down the group an element is, the higher its relative molecular mass, melting point, and boiling point. Signup and view all the answers

Describe the halogen fluorine.

Fluorine is a very reactive, poisonous yellow gas. Signup and view all the answers

Describe the halogen chlorine.

Chlorine is a fairly reactive, poisonous dense green gas. Signup and view all the answers

Describe the halogen bromine.

Bromine is a dense, poisonous red-brown volatile liquid. Signup and view all the answers

Describe the halogen iodine.

Iodine is a dark grey crystalline solid or purple vapour. Signup and view all the answers

Compare transition metals with Group 1 metals.

Group 1 metals are much more reactive than transition metals; they react more vigorously with water, oxygen, or Group 7 elements. Signup and view all the answers

What trends are observed in halogens?

As you go down Group 7, the halogens become less reactive, have higher melting and boiling points, and higher relative atomic masses. Signup and view all the answers

What is the concept of displacement of halogens?

More reactive halogens will displace less reactive halogens; for example, chlorine can displace bromine and iodine from their salts. Signup and view all the answers

Study Notes

Periodic Table Arrangement

Elements are ordered by atomic (proton) number, creating groups with similar properties.
The term "periodic" reflects the recurrence of similar properties at regular intervals.

Group Characteristics

Elements in the same group share the same number of outer shell electrons, leading to similar chemical behaviors.

Early Element Classification

Prior to proton, neutron, and electron discovery, classification was based on atomic weights.
Early periodic tables often placed elements incorrectly due to strict adherence to atomic weights.

Mendeleev's Contribution

Dimitri Mendeleev improved classification by leaving gaps for undiscovered elements and adjusting order based on properties.
His predictions for undiscovered elements were later confirmed with actual discoveries.

Isotopes and Atomic Weight

Understanding isotopes clarified discrepancies within atomic weight-based ordering.

Metals vs. Non-Metals

Metals form positive ions and are located on the left and bottom of the periodic table.
Non-metals do not form positive ions and are found towards the right and top.

Properties of Metals

Metals are strong, malleable, good conductors of heat/electricity, and have high melting/boiling points.
All metals exhibit metallic bonding.

Properties of Non-Metals

Non-metals lack metallic bonding, are dull, brittle, and often gaseous at room temperature.
They generally do not conduct electricity and have lower densities.

Noble Gases (Group 0)

Group 0 elements, or noble gases, are unreactive with stable electron arrangements, mostly consisting of colorless monatomic gases.
Their boiling points rise with atomic mass due to increased intermolecular forces.

Alkali Metals (Group 1)

Group 1 elements, known as alkali metals, have one outer shell electron, making them highly reactive.
Reactivity increases down the group, alongside decreasing melting/boiling points and increasing atomic mass.

Alkali Metals and Reactions

Alkali metals react vigorously with water, producing hydrogen gas and metal hydroxides.
Reactions with chlorine yield white metal chlorides and become more vigorous down the group.
They also form metal oxides upon reacting with oxygen, exhibiting varied products.

Halogens (Group 7)

Halogens possess seven outer shell electrons and form diatomic molecules, showing colored vapors.
Reactivity decreases down the group, while melting/boiling points and relative molecular masses increase.

Specific Halogen Properties

Fluorine: Very reactive, poisonous yellow gas.
Chlorine: Fairly reactive, dense poisonous green gas.
Bromine: Dense, red-brown volatile liquid that is also poisonous.
Iodine: Appears as dark grey crystalline solid or purple vapor.

Transition Metals vs. Group 1

Transition metals are less reactive than alkali metals but are stronger, denser, and typically have higher melting points.
Transition elements often form colored compounds and have variable ionic charges.

Displacement Reactions in Halogens

More reactive halogens can displace less reactive ones in aqueous solutions, demonstrating the trend in reactivity.

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Description

Explore the arrangement of the periodic table, including how elements are classified by atomic number and their group characteristics. Dive into the contributions of Mendeleev and the significance of isotopes in understanding atomic weights.