Actinides

Actinides are a series of 15 metallic elements on the Periodic Table, from Actinium (Ac, 89)

through Lawrencium (Lr, 103).

These elements are radioactive and are mainly synthetically created.

Actinides usually have multiple oxidation states and are highly reactive.

These elements are used in nuclear industry and medical research.

Actinides have partially-filled f-orbitals, leading to their electron configurations.

Alkali Metals

Alkali metals, comprising Group 1 of the periodic table, are highly reactive elements due to their

single valence electron.

They include lithium, sodium, potassium, rubidium, cesium, and francium.

Alkali metals have low densities and soft enough to cut with a knife.

They quickly tarnish in air and react violently with water.

These metals form alkaline solutions, hence their name.

Aluminum

Aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft,

nonmagnetic and ductile metal.

Aluminum is known for its low density and high strength-to-weight ratio, making it popular for

use in aircraft construction.

The metal is highly resistant to corrosion, due to its ability to form a protective oxide layer.

Aluminum is the most abundant metal in the Earth's crust, but it never occurs in its pure form.

It is commonly used in everyday items such as beverage cans, foil, and kitchen utensils.

Anions

Anions are negatively charged ions formed when atoms gain electrons.

Anions are attracted to the positively charged ions, known as cations.

The presence of anions can affect the chemical properties of a substance.

Anions can form ionic bonds with cations to create compounds.

Anions are often involved in chemical reactions due to their high reactivity.

As the valence electrons increase

As the valence electrons increase, the reactivity of an element towards forming chemical bonds

also increases due to greater electron availability.

Elements with full valence electron shells are stable and less likely to form bonds.

Valence electrons determine an element's chemical properties and how it interacts with other

elements.

The group number on the periodic table indicates the number of valence electrons in an

element.

Valence electrons participate in forming chemical bonds with other atoms to achieve a stable

electron configuration.

As you move ACROSS a period

As you move across a period in the periodic table, the atomic number increases left to right,

resulting in an increase in the number of protons and electrons.

Atomic size decreases as the effective nuclear charge increases.

Electron affinity generally increases, except for noble gases.

Ionization energy generally increases as you move across a period.

Nonmetals are located on the right side of the periodic table.

As you move DOWN a group

Moving down a group on the periodic table involves elements with increasing atomic number

and additional electron shells, leading to greater atomic size and reactivity.

Each subsequent element will have one additional electron shell compared to the one above

it.

Atomic radius tends to increase due to added electron shells, while ionization energy

decreases as electrons are farther from the nucleus.

Reactivity may increase as the outermost electrons are further away from the nucleus and

easier to lose.

The pattern of properties repeating every period is due to the similar electron configurations

within each group.

atomic radius

Atomic radius refers to the size of an atom from the center of its nucleus to its outermost

electron orbital.

Atomic radius decreases across a period as increased nuclear charge attracts electrons

closer.

It increases down a group due to additional electron shells.

Covalent radius and van der Waals radius are types of atomic radii.

Factors influencing atomic radius include atomic number and electron configuration.

Bromine

Bromine is a chemical element with the symbol Br and atomic number 35. It is a red-brown,

corrosive liquid, and a member of the halogen group.

Bromine is the only nonmetallic liquid element at room temperature.

It is highly reactive and can react violently with metals, nonmetals, and even water.

Bromine is widely used as a flame retardant in many industries.

Its compounds are commonly used in pharmaceuticals, agrochemicals, and dyes.

Cations

Cations are positively charged ions that are formed when an atom loses electrons. They are

usually formed by metals.

Cations have a positive charge and are attracted to negatively charged ions called anions.

Cations are typically smaller in size than the parent atom due to the loss of electrons.

Cations play a crucial role in many chemical reactions and are often involved in the formation

of compounds.

The number of cations in a compound must balance the number of anions to maintain

electrical neutrality.

Columns

In the context of columns, these are vertical elements in the periodic table that share similar

chemical properties and electron configurations.

Columns are also known as groups and contain elements with the same number of valence

electrons.

The elements in the same column tend to exhibit similar patterns in terms of reactivity and

chemical behavior.

The columns are labeled numerically from 1 to 18 on the periodic table.

Understanding columns helps in predicting an element's characteristics based on its position

in the periodic table.

Diatomic elements

Diatomic elements are those composed of two identical atoms bonded together, such as

hydrogen (H2) and oxygen (O2). They form molecules in pairs.

Seven elements exist naturally as diatomic molecules, including hydrogen, nitrogen, oxygen,

fluorine, chlorine, bromine, and iodine.

Diatomic elements are often found in their gaseous state at room temperature.

These elements are important in understanding chemical reactions and balancing equations.

They are commonly encountered in nature, such as oxygen in the air and hydrogen in water.

Dmitri Mendeleev

Dmitri Mendeleev was a Russian scientist who is best known for creating the periodic table, a

tool used to organize and classify elements based on their chemical properties.

He arranged the elements in order of increasing atomic mass, leaving gaps for undiscovered

elements that were later confirmed.

Mendeleev's periodic table allowed for the prediction of the properties of these undiscovered

elements.

He published his first version of the periodic table in 1869.

Mendeleev's periodic table formed the foundation for the modern periodic table used today.

Electronegativity

Electronegativity refers to the tendency of an atom to attract electrons towards itself when it is

part of a chemical bond.

Electronegativity values range from 0.7 to 4.0.

Elements with higher electronegativity tend to have a stronger attraction for electrons.

The difference in electronegativity between bonding atoms determines the type of chemical

bond formed.

Electronegativity increases across a period and decreases down a group on the periodic

table.

Elements with less than 4 valence electrons

Elements with less than 4 valence electrons tend to lose electrons to achieve a stable octet,

forming positive ions.

Alkali metals like sodium have 1 valence electron.

Alkaline earth metals such as magnesium have 2 valence electrons.

Boron, with 3 valence electrons, tends to form covalent bonds.

Elements with 4 or more valence electrons can share, gain, or lose electrons to reach stability.

Elements with more than 4 valence electrons

Elements with more than 4 valence electrons tend to be nonmetals and include sulfur,

phosphorus, and chlorine. They are more likely to gain electrons.

These elements have a tendency to form negative ions when they react with other elements.

Having more than 4 valence electrons makes these elements more likely to participate in

covalent bonding.

Elements with more than 4 valence electrons are typically found in groups 15, 16, and 17 of

the periodic table.

The number of valence electrons in an element determines its reactivity and chemical

behavior.

Fluorine

Fluorine is a highly reactive element with symbol F and atomic number 9. It is the lightest

halogen and exists as a pale yellow gas.

Fluorine has the highest electronegativity among all the elements.

It readily reacts with almost all other elements, including metals and non-metals.

Fluorine is used in the production of fluorinated compounds, such as Teflon and Freon.

It is added to drinking water and toothpaste to prevent dental cavities.

Gaseous Elements

Gaseous elements exist in a state where individual atoms are not bonded together, exhibiting

high mobility and filling any container they are in.

Gaseous elements have low boiling points and high vapor pressures compared to other

elements.

They can be found in Group 18 of the periodic table and are known as the noble gases.

Examples include helium, neon, argon, and xenon.

These elements are often used in lighting, refrigeration, and various industrial processes.

Group 1

Group 1 elements are highly reactive metals that include Lithium, Sodium, and Potassium. They

exhibit a single electron in their outer shell.

They are soft metals that can be easily cut with a knife.

Group 1 metals react vigorously with water to form hydroxides and release hydrogen gas.

These elements are stored under oil to prevent them from reacting with moisture in the air.

They are used in various applications such as batteries, fireworks, and making soaps.

Group 2

Group 2 elements, also known as alkaline earth metals, include beryllium, magnesium, calcium,

strontium, barium, and radium. They have 2 valence electrons.

They are located in the second column of the periodic table.

Group 2 metals are reactive but less than Group 1 alkali metals.

They have a shiny appearance and are good conductors of heat and electricity.

These elements readily form 2+ positive ions.

Group 7

Group 7 elements, also known as the halogens, consist of fluorine, chlorine, bromine, iodine, and

astatine. They are highly reactive nonmetals.

Halogens have seven electrons in their outer shell, making them only one electron short of

achieving a full valence shell.

Halogens readily form halide ions by gaining an electron, making them negative ions.

Group 7 elements exhibit a trend of decreasing reactivity down the group, with fluorine being

the most reactive halogen.

Halogens are diatomic molecules in their natural state, meaning they exist as pairs of atoms

bonded together.

Group 8

Group 8 contains elements known as the noble gases, including helium, neon, argon, krypton,

xenon, and radon. These elements possess full outer electron shells, making them chemically

stable.

Noble gases are nonreactive due to their stable electron configuration.

Helium is the lightest noble gas, while radon is the heaviest and radioactive.

Noble gases are used in lighting, such as neon signs, and in welding to provide an inert

atmosphere.

The noble gases are located in the far-right column of the periodic table.

Halogens

Halogens are a group of elements on the periodic table known for their reactivity and ability to

form salts.

They include fluorine, chlorine, bromine, iodine, and astatine.

Halogens have seven valence electrons, making them highly reactive.

They can form diatomic molecules, such as Cl2 or F2.

Halogens can displace less reactive halogens from their compounds.

Henry Mosley

Henry Mosley was a British physicist who developed the concept of atomic numbers, leading to

the modern organization of the periodic table.

He determined the atomic numbers of elements through X-ray spectroscopy.

His work established the arrangement of elements based on atomic numbers, rather than

atomic weights.

Mosley's discoveries provided a more accurate understanding of the periodic table.

His research laid the foundation for the periodic laws that govern the elements.

Hydrogen

Hydrogen is a colorless, odorless, tasteless gas and the lightest and most abundant element in

the universe.

It occupies the first position on the periodic table.

It's primarily used in the production of ammonia and methanol.

It has one proton and one electron.

Hydrogen bonds are crucial in biochemistry, helping to form DNA and proteins.

Iodine & Sulfur

Iodine and sulfur are both nonmetals that can react to form compounds like iodine monosulfide

(I2S) and elemental sulfur (S8).

Iodine has a purple color while sulfur is yellow, aiding in distinguishing between the two

elements.

Sulfur is typically found in its solid form, while iodine can sublimate from a solid to a vapor.

Iodine and sulfur both have varying oxidation states, contributing to a wide range of possible

chemical reactions involving the elements.

Combining iodine and sulfur can lead to the formation of compounds with unique properties,

such as their distinct colors and bonding characteristics.

ion

An 'ion' refers to an atom or molecule with a net electric charge due to the loss or gain of one or

more electrons.

An atom can gain an electron to form a negatively charged ion, known as an anion.

An atom may also lose an electron and form a positively charged ion, called a cation.

Ions play significant roles in processes like electrolysis, cellular communication, and

conduction of electricity in solutions.

Ionic bonding, which involves the transfer and acceptance of electrons, results in the

formation of ions.

Ionic radii

Ionic radii refer to the size of ions, which are atoms or molecules that have gained or lost

electrons, affecting their radius.

Ionic size tends to increase as electrons are added, and decrease when electrons are lost.

Size variation is influenced by the number of electron shells and effective nuclear charge.

Cations (positively charged ions) are smaller in size than anions (negatively charged ions)

with the same electron configuration.

Ionic radius is an important factor in determining the structure and properties of ionic

compounds.

Ionization energy

Ionization energy refers to the energy required to remove an electron from a gaseous atom or

ion. It's measured in kilojoules per mole (kJ/mol) or electron Volts (eV)

Higher nuclear charge and lower electron shielding increase ionization energy

Different atoms have different ionization energies, reflecting their unique electron

configurations

Ionization energy generally increases across a period and decreases down a group in the

periodic table

First ionization energy is the energy to remove the first, outermost electron. Subsequent

ionization energies increase.

lanthanides

Lanthanides are a group of 15 metallic elements, from atomic numbers 57 to 71, found in the

periodic table's f-block.

Lanthanides include elements like Lanthanum, Cerium, Praseodymium, etc.

They are often called 'rare earth metals' given their dispersed presence in earth's crust.

Lanthanides have a similar chemical behavior due to their similar outer electron

configuration.

They are widely used in industries for manufacturing electronic devices, batteries, and lasers.

Less shielding

Less shielding refers to a situation where electrons in outer energy levels experience greater

nuclear attraction, leading to higher ionization energy and smaller atomic size.

Higher ionization energy makes it harder to remove outer electrons.

Trends in atomic size become more pronounced.

Elements may form more covalent bonds.

Can affect chemical reactivity and bond strength.

Mercury

Mercury is a silvery-white metal that is a liquid at room temperature and has a high density. It is

used in thermometers, barometers, and fluorescent lights.

Mercury is highly toxic and should be handled with caution.

It has a unique property of forming amalgams with other metals.

Mercury does not react with most acids and is a poor conductor of heat.

It has a historical use in dental fillings, although this is now being phased out.

Mercury & Bromine

Mercury is a liquid metal with symbol Hg and atomic number 80, while bromine is a halogen

element with the symbol Br and atomic number 35.

Mercury has a silvery appearance and is known for its high density.

Bromine is a red-brown liquid at room temperature and is highly reactive.

Mercury is often used in thermometers and barometers.

Bromine is a key component in flame retardants.

Both elements have industrial applications in various fields.

Metalloids

Metalloids are elements with properties between metals and non-metals. They appear in a stairstep

line on the periodic table.

Metalloids are semiconductors, useful in electronic devices.

Their reactivity depends on the element they are interacting with.

Silicon, germanium, arsenic, antimony, and tellurium are major metalloids.

They exhibit variable physical properties like lustre or lack thereof.

Metals

Metals are malleable, ductile, and conductive materials found on the left side of the periodic

table. They are usually shiny and solids at room temperature.

Metals form positive ions (cations) by losing electrons in reactions.

Most metals react with oxygen to form metal oxides.

They generally have high melting and boiling points.

Metals can form alloys by combining with other metals.

More shielding

More shielding refers to inner electron layers reducing the attraction between the nucleus and

outer electrons, decreasing effective nuclear charge.

This results in the outer electrons being held less tightly.

Shielding increases down a group due to additional energy levels.

Effective nuclear charge affects properties like ionization energy and atomic size.

Shielding can impact chemical reactivity and the formation of bonds.

Mosley

In the context of Mosley, it refers to the scientist Henry Mosley, known for the periodic law and

the concept of atomic numbers.

Mosley's work led to the organization of elements on the periodic table based on atomic

number.

He discovered that each element has a unique atomic number, which is equal to the number

of protons in its nucleus.

Mosley's contributions were crucial in developing the modern periodic table.

His research helped establish a more accurate understanding of the physical and chemical

properties of elements.

Noble Gases

Noble Gases, elements in group 18 of the periodic table, are colorless, odorless, and extremely

unreactive due to their full electron shell.

Examples include Helium, Neon, Argon, Krypton, Xenon, and Radon.

The low reactivity makes them stable and suitable for neon lights and helium balloons.

Noble Gases exhibit a glow when electric current passes through them.

Despite their inertness, some noble gases can form compounds under extreme conditions.

Nonmetals

Nonmetals are elements that typically lack the physical characteristics of metals and have

properties opposite to them, including conductivity, malleability, and luster.

There are 17 nonmetals on the Periodic Table, including hydrogen, oxygen, and carbon.

Nonmetals usually have high ionization energies and electronegativities.

Most nonmetals can gain electrons during reactions.

Nonmetals often form covalent bonds with other nonmetals.

Periodic Law

Periodic Law refers to the concept where elements arranged by atomic number show repeating,

or periodic, properties.

Mendeleev and Meyer are credited with being most responsible for the modern periodic law.

Periodicity dictates many elemental properties, such as reactivity.

This law is fundamental in the study of atomic structure and electronic configuration.

Periodic Table

The "Periodic Table" organizes all known elements based on their atomic number, electron

configuration, and recurring properties.

Initially built by Dmitri Mendeleev in 1869

Atomic number corresponds to the number of protons

Elements in the same group have similar properties

Periods represent energy levels or shells of electrons

Radon

Radon is a colorless, odorless, radioactive element found in the environment. It is formed as a

decay product of uranium and is the heaviest known noble gas.

Radon is a potential health risk and exposure to high levels can increase the risk of lung

cancer.

It can be found in the soil, air, and water, and can enter homes through cracks and gaps in the

foundation.

Radon levels can vary depending on geographic location and the type of soil.

Testing for radon in homes is important to ensure that levels are within the safe range to

protect occupants.

Reactivity

Reactivity is the propensity of an element or compound to undergo a chemical reaction with

another substance under certain conditions.

The reactivity of elements varies and is dictated by the element's electron configuration.

Highly reactive substances interact with other substances quite readily.

Reactivity can be influenced by certain conditions such as temperature and pressure.

In general, metals tend to be more reactive than nonmetals.

Rows

Rows in the periodic table are horizontal arrangements of elements that share similar properties.

Each row represents a new energy level.

Rows are also known as periods and indicate the number of electron shells an element's

atoms have.

Elements within the same row have the same number of electron shells but differ in the

number of electrons in the outer shell.

As you move from left to right across a row, the atomic number of the elements increases.

Chemical reactivity tends to decrease as you move from left to right within a row.

The Lewis Dot Effect

The Lewis Dot Effect explains the tendency for atoms to attain a stable electron configuration by

gaining, losing, or sharing electrons with other atoms.

Atoms achieve stability by acquiring the electron arrangement of a noble gas.

Valence electrons are depicted as dots in Lewis dot structures.

The Lewis Dot Effect aids in understanding chemical bonding and reactivity.

It provides a visual representation of electron distribution in molecules.

The Octet Rule

The Octet Rule states that atoms tend to gain, lose, or share electrons to achieve a stable

configuration with 8 electrons in their outer shell.

Atoms follow the Octet Rule to achieve stability by having a full outer electron shell.

In Lewis structures, atoms are depicted surrounded by valence electrons to adhere to the

Octet Rule.

The Octet Rule is most commonly observed among main group elements.

Exceptions to the Octet Rule include atoms with fewer or more than 8 valence electrons.

The Shielding Effect

The Shielding Effect refers to the phenomenon where inner electrons shield outer electrons from

full attraction to the nucleus.

It leads to a decrease in the effective nuclear charge felt by the outer electrons.

Shielding is greater in elements with multiple electron shells.

The shielding effect helps explain variations in atomic and ionic sizes across the periodic

table.

Electron shielding impacts the ease with which elements gain or lose electrons.

Transition metals

Transition metals are a group of elements that are located in the middle of the periodic table,

known for their ability to form multiple oxidation states and their unique electron configurations.

Transition metals often exhibit colorful compounds due to the presence of partially filled dorbitals.

These metals are typically good conductors of heat and electricity.

Transition metals play important roles in catalysis, helping to speed up chemical reactions.

They are commonly used in the production of alloys, such as stainless steel and bronze.

Trends

Trends in this context refer to the predictable variations of properties as you move across the

periodic table from left to right or top to bottom.

Atomic size generally increases down a group and decreases across a period.

Ionization energy tends to decrease down a group and increase across a period.

Electronegativity typically increases across a period and decreases down a group.

Metallic character decreases across a period and increases down a group.

Unknown term

In the context of Chemistry, an 'unknown term' refers to a term or concept that is not familiar or

has not been defined in the specific topic being studied.

The 'unknown term' can often require further research or clarification to fully understand its

meaning and relevance.

It is important for students to review their study materials and resources to identify and

clarify any 'unknown terms' they come across.

Seeking assistance from teachers or peers can also be helpful in defining and understanding

'unknown terms' in Chemistry.

Identifying and understanding 'unknown terms' is crucial for comprehending and effectively

applying the concepts and principles of Chemistry.

Valence Electrons

Valence Electrons are the outermost electrons of an atom and play a key role in determining its

chemical reactivity and bonding.

Valence Electrons either are shared, lost, or gained in chemical reactions.

The number of Valence Electrons helps to determine the group of the atom in the Periodic Table.

They are directly involved in forming chemical bonds with other atoms.

Different elements have different numbers of valence electrons ranging from 1 to 8