Chemistry Unit 5

Who grouped elements into triads based on similar properties?

J.W. Dobereiner

What did John Newlands propose in 1865?

The law of octaves, organizing elements by atomic weight.

What was Mendeleev known for in the development of the periodic table?

He published the first periodic table and predicted undiscovered elements.

How is the modern periodic table arranged?

By increasing atomic number.

What are periods in the periodic table?

Horizontal rows where properties change across.

What are groups or families in the periodic table?

Vertical columns where elements share similar properties.

What is the IUPAC numbering system for groups?

1-18.

What are alkali metals known for?

Being highly reactive and forming 1+ cations.

What characterizes alkaline earth metals?

They are reactive and form 2+ cations.

What are halogens known for?

Having high electron affinities and forming 1- anions.

What is a defining feature of noble gases?

They have a full valence shell and are relatively nonreactive.

What are the properties of metals?

Good conductors, shiny, malleable, ductile, mostly solid.

What distinguishes nonmetals from metals?

Poor conductors and tend to be brittle solids or gases.

What are metalloids?

Elements with properties intermediate between metals and nonmetals.

What determines an element's chemical and physical properties?

Its electron configuration, particularly the outer shell electrons.

What is the significance of blocks in the periodic table?

They help visualize electron configurations and predict reactivity.

What is Coulomb's Law equation?

F = keq1q2/d2.

What does the force in Coulomb's Law depend on?

The charge of the particles and the distance between them.

What is the shielding effect?

The reduction of the attractive force of the nucleus on valence electrons.

What is effective nuclear charge (Zeff)?

The net positive nuclear charge experienced by an electron.

How does Zeff trend across a period?

Zeff increases from left to right.

What happens to atomic radius across a period?

It decreases from left to right.

What is the trend for ionic size of cations?

Cations are always smaller than their parent atoms.

What is the trend for ionic size of anions?

Anions are always larger than their parent atoms.

What is the general trend for atomic radius down a group?

It increases from top to bottom.

What is the smallest element in the periodic table?

Helium.

What is the largest element in the periodic table?

Francium.

What is ionization energy?

The energy required to remove the outermost electron from the ground state of a gaseous atom.

How does ionization energy change across a period?

Ionization energy generally increases from left to right across a period.

How does ionization energy change down a group?

Ionization energy generally decreases from top to bottom down a group.

What are successive ionization energies?

Each successive ionization energy is higher than the last because it's harder to remove an electron from an increasingly positive ion.

What does a large jump in ionization energy indicate?

It indicates the removal of a core electron.

How does atomic size relate to ionization energy?

Smaller atoms tend to have higher ionization energies.

What are noble gases known for regarding ionization energy?

Noble gases have very high ionization energies due to their stable, full valence shells.

How do metals and nonmetals differ in terms of ionization energy?

Metals have low ionization energies (tend to lose electrons), while nonmetals have higher ionization energies (tend to gain electrons).

What is electron affinity?

The energy change that occurs when an atom gains an electron.

How does electron affinity change across a period?

Electron affinity generally increases (becomes more negative) from left to right in Groups 15-17.

What is the electron affinity of noble gases?

Noble gases have very low electron affinities (positive or near zero) because they have full valence shells.

What is metallic character?

The tendency of an element to lose electrons and form cations.

How does metallic character change down a group?

Metallic character increases down a group.

How does metallic character change across a period?

Metallic character decreases across a period from left to right.

What is nonmetallic character?

The tendency of an element to gain electrons and form anions.

How does nonmetallic character change across a period?

Nonmetallic character increases across a period from left to right.

How does nonmetallic character change down a group?

Nonmetallic character decreases down a group.

What is periodicity?

The repeating pattern of properties when elements are arranged by atomic number.

What is the predictive power of the periodic table?

The periodic table allows scientists to predict properties of undiscovered elements or compare properties of known elements based on their position.

How did Mendeleev's approach differ from Newlands' in organizing the periodic table?

Mendeleev organized elements by atomic mass and properties, leaving gaps for undiscovered elements, while Newlands proposed a 'law of octaves' without accounting for undiscovered elements.

What is a period in the periodic table?

A period is a horizontal row in the periodic table, where properties change systematically.

What is a group in the periodic table?

A group (or family) is a vertical column, and elements within the same group share similar properties due to similar valence electron configurations.

What are the key properties of metals?

Metals are good conductors of heat and electricity, shiny, and malleable.

What are the key properties of nonmetals?

Nonmetals are generally poor conductors, lack luster, and solid nonmetals tend to be brittle.

What is a metalloid?

A metalloid is an element with properties intermediate between metals and nonmetals.

Where are metalloids located on the periodic table?

Metalloids are found in a zigzag pattern on the periodic table.

How can the conductivity of metalloids be manipulated?

Their conductivity can be manipulated, for example, by mixing silicon with boron to create semiconductors.

What is Coulomb's Law?

Coulomb's Law states that the force between two charged particles is directly proportional to their charges and inversely proportional to the square of the distance between them.

How does distance affect the force of attraction according to Coulomb's Law?

As the distance between charged particles increases, the force of attraction between them weakens significantly.

How does Zeff change across a period?

Zeff generally increases from left to right across a period.

What is the trend for atomic radius across a period?

Atomic radius decreases across a period from left to right.

What is the trend for atomic radius down a group?

Atomic radius increases down a group from top to bottom.

Why are cations smaller than their parent atoms?

Cations are always smaller than their parent atoms because they lose electrons, reducing electron-electron repulsion.

Why are anions larger than their parent atoms?

Anions are always larger than their parent atoms because they gain electrons, increasing electron-electron repulsion.

How does ionization energy relate to the stability of an element's electron configuration?

Ionization energy is related to stability because noble gases have high ionization energies due to their stable, full valence shells.

What increases down a group in the periodic table?

Atomic radius increases down a group.

What generally happens to atomic radius as you move up and to the right on the periodic table?

Atomic radius generally decreases.

How does ionization energy relate to stability?

Elements with stable electron configurations, like noble gases, have very high ionization energies.

Who contributed to the historical development of the periodic table?

Dobereiner, Newlands, and Mendeleev.

What did Mendeleev's work contribute to the periodic table?

He observed patterns and made predictions about undiscovered elements.

What does Coulomb's Law describe?

The force of attraction or repulsion between two charged particles.

What are alkali metals?

Elements in Group 1 of the periodic table, known for being highly reactive and easily losing one electron to form 1+ cations.

What are alkaline earth metals?

Elements in Group 2 of the periodic table, reactive metals that tend to lose two electrons to form 2+ cations.

What is an anion?

An atom or group of atoms that has gained one or more electrons, resulting in a net negative charge.

What is an atomic number?

The number of protons in the nucleus of an atom, which uniquely identifies an element.

What is atomic radius?

One-half the distance between the nuclei of two atoms of the same element.

What is a cation?

An atom or group of atoms that has lost one or more electrons, resulting in a net positive charge.

What are core electrons?

Electrons in the inner shells of an atom that shield the valence electrons from the nucleus.

Who was Dimitri Mendeleev?

A Russian chemist credited with significant contributions to the periodic table.

What does ductile mean?

A property of metals meaning they can be pulled and stretched into wires.

What is electron configuration?

The arrangement of electrons around the nucleus of an atom.

What are halogens?

Elements in Group 17 of the periodic table, highly reactive nonmetals.

Who was J.W. Dobereiner?

A German chemist who arranged elements into groups of three based on similar properties.

What is the significance of valence electrons?

They determine an element's reactivity and position within a specific group.

What is the periodic law?

States that when elements are arranged by increasing atomic number, there is a periodic repetition of their properties.