Electron Configuration and Periodic Table History

Questions and Answers

Why are there exceptions to the electron configuration rules?

Exceptions to the Aufbau principle are based on the fact that a few atoms are more stable when their electrons fill or half-fill an electron shell or subshell.

Define electron configuration.

The distribution of electrons of an atom or molecule in atomic or molecular orbitals.

How was the periodic table arranged in the past?

Based on physical properties.

Who is Johann Dobereiner?

He classified some elements into groups of three, called triads. Signup and view all the answers

What is the Halogen Triad?

Chlorine, bromine, iodine. Signup and view all the answers

What does the Law of Octaves propose?

The same properties appear every eighth element when listed in order of atomic masses. Signup and view all the answers

Who published a table of the elements organized by increasing atomic mass?

Dmitri Mendeleev. Signup and view all the answers

Who is Lothar Meyer?

He published a table of elements organized by increasing atomic mass around the same time as Mendeleev. Signup and view all the answers

Why is Mendeleev called the 'father of the modern periodic table'?

He predicated undiscovered elements and corrected atomic masses of elements. Signup and view all the answers

What is the role of Henry Moseley in periodic table development?

He arranged elements by increasing atomic number. Signup and view all the answers

What did Glenn T. Seaborg do?

Moved 14 elements out of the main body of the periodic table to form the 'Actinide' series and co-discovered 10 new elements. Signup and view all the answers

What is the periodic law?

The physical and chemical properties of elements are periodic functions of their atomic numbers. Signup and view all the answers

What are periods in the periodic table?

Rows on the periodic table. Signup and view all the answers

What are groups or families in the periodic table?

Vertical columns on the periodic table. Signup and view all the answers

What is a chemical symbol?

A one or two-letter abbreviation for the name of an element. Signup and view all the answers

Define atomic number.

Number of protons in the nucleus or electrons in the electron cloud. Signup and view all the answers

What is atomic mass?

Combined number of protons and neutrons in the nucleus. Signup and view all the answers

What are valence electrons?

Electrons on the outermost energy level of an atom. Signup and view all the answers

How many valence electrons can an atom have?

1 to 8. Signup and view all the answers

What are valence electrons used for?

To bond to other atoms to form compounds. Signup and view all the answers

How do you determine the number of valence electrons?

Look at the group number the element is in, ignoring transition elements. Signup and view all the answers

What kind of elements make up most of the periodic table?

Metals. Signup and view all the answers

What are metalloids?

Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Astatine. Signup and view all the answers

List the properties of metals.

Lustrous, malleable, ductile, good conductors. Signup and view all the answers

What are the properties of nonmetals?

Dull, brittle, poor/non-conductors. Signup and view all the answers

What are the properties of metalloids?

Have characteristics of both metals and nonmetals. Signup and view all the answers

What is a semiconductor?

Elements that have conduction capacities between nonmetals and metals. Signup and view all the answers

When does atomic radius increase on the periodic table of elements?

As you move down the vertical columns (groups/families). Signup and view all the answers

Why does atomic radius increase in columns?

Each step down adds an entirely new energy level to the electron cloud. Signup and view all the answers

When does atomic radius decrease on the periodic table?

From left to right in rows on the periodic table. Signup and view all the answers

Why does atomic radius decrease across a period?

The nucleus has a greater pull on the electron cloud as more protons are added. Signup and view all the answers

What is electron shielding?

Inner levels of electrons shield the outer electrons from the nucleus' attraction. Signup and view all the answers

When is an atom 'ionized'?

When an electron is pulled toward another atom with enough energy to overcome nuclear attraction. Signup and view all the answers

If an atom loses an electron, what happens?

It becomes positively charged. Signup and view all the answers

If an atom gains an electron, what happens?

It becomes negatively charged. Signup and view all the answers

What is ionization energy?

The energy required to remove an electron from an atom. Signup and view all the answers

What happens if an atom is larger?

It loses electrons easier. Signup and view all the answers

Are ionization energy and atomic radius directly or inversely proportional?

Inversely proportional. Signup and view all the answers

What is electron affinity?

The energy change that occurs when an atom gains an electron. Signup and view all the answers

What is metallic character?

A relative measure of how easily atoms lose or give up electrons. Signup and view all the answers

Define electronegativity.

An atom's attraction for another atom's electrons. Signup and view all the answers

What is the unit for electronegativity?

Pauling scale. Signup and view all the answers

How does electronegativity work on the periodic table?

Increases left to right, decreases top to bottom. Signup and view all the answers

What is the overall reactivity trend for metals?

Most reactive are the largest since they are the best electron givers. Signup and view all the answers

What is the overall reactivity trend for nonmetals?

Most reactive are the smallest ones, the best electron takers. Signup and view all the answers

What is the octet rule?

Atoms aim to have a group of 8 electrons in their valence energy level. Signup and view all the answers

What is an anion?

When an atom gains an electron, it becomes negatively charged. Signup and view all the answers

What is a cation?

Metal atoms can lose electrons, becoming positively charged. Signup and view all the answers

What is the ionic radius for cations?

Cations are always smaller than the original atom. Signup and view all the answers

What is the ionic radius for anions?

Anions are always larger than the original atom. Signup and view all the answers

What are noble gases?

Nonreactive gases that are monoatomic and almost inert in group 18. Signup and view all the answers

What are alkali metals?

Soft metals in Group 1 with an s1 configuration, very reactive with air or water. Signup and view all the answers

What are alkaline earth metals?

Metals in Group 2 with an s2 configuration, harder and less reactive than alkali metals. Signup and view all the answers

What are transition elements?

Elements in groups 3 through 12, usually harder and less reactive. Signup and view all the answers

What are lanthanides?

The 4f series of metals with atomic numbers 57-71, shiny and reactive. Signup and view all the answers

What are actinides?

The 5f series of metals with atomic numbers 89-103, all radioactive. Signup and view all the answers

What are main block elements?

Metals in groups 13 through 18. Signup and view all the answers

What are halogens?

Elements in Group 7, most reactive nonmetals forming salts with Group 1 metals. Signup and view all the answers

What are chalcogens?

Elements in Group 6 that often gain two electrons to achieve stability. Signup and view all the answers

What properties do noble gases exhibit?

They have filled electron shells and are very stable and nonreactive. Signup and view all the answers

What defines hydrogen's unique position on the periodic table?

Hydrogen can give away or gain an electron, acting as either a metal or a nonmetal. Signup and view all the answers

What is the shielding effect with ionization energy?

Inner electrons shield outer electrons from the positive nucleus. Signup and view all the answers

What is the Heisenberg uncertainty principle?

It is impossible to know both the velocity and position of a particle at the same time. Signup and view all the answers

What are the electron cloud levels?

Principal energy level, sublevel, orbital. Signup and view all the answers

How many principal energy levels are there?

Seven. Signup and view all the answers

What are subshells and orbitals?

s, p, d, f. Signup and view all the answers

Where does the modern quantum mechanical model come from?

The mathematical solutions to the Schrödinger equation. Signup and view all the answers

What is an atomic orbital?

A region of space with a high probability of finding an electron. Signup and view all the answers

What is the shape of an s orbital?

Spherical. Signup and view all the answers

What is the shape of a p orbital?

Dumbbell (can be Px, Py, and Pz). Signup and view all the answers

What are the number of electrons for the first four energy levels?

2, 8, 18, 32. Signup and view all the answers

What does the Aufbau principle state?

An electron occupies the lowest-energy orbital that can receive it. Signup and view all the answers

Which groups have filled s orbitals?

Groups 1A and 2A. Signup and view all the answers

Which groups have filled p orbitals?

Groups 3A - 8A. Signup and view all the answers

Which groups have filled d orbitals?

Groups 3B - 2B. Signup and view all the answers

Which groups have filled f orbitals?

The lanthanides and actinides. Signup and view all the answers

How to abbreviate electron configurations?

Indicate the innermost electrons with the symbol of the preceding noble gas. Signup and view all the answers

Why are there electron configurations that are exceptions?

Because half-filled sublevels are more stable than other configurations. Signup and view all the answers

What is the d^4 and d^9 rule?

These configurations are unstable and will steal electrons from the s-sublevel to stabilize. Signup and view all the answers

What is the Pauli Exclusion Principle?

A maximum of two electrons may occupy a single orbital with opposite spins. Signup and view all the answers

What is Hund's Rule?

Single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins. Signup and view all the answers

What is the order of electron configuration?

Electrons fill up empty orbitals before sharing with other electrons. Signup and view all the answers

What are quantum numbers?

Numbers used to describe the probable location of electrons. Signup and view all the answers

What is the principal quantum number?

Symbolized by n, indicates the main energy level occupied by the electron. Signup and view all the answers

What is the angular momentum (azimuthal) quantum number?

Symbolized by l, indicates the shape of the orbital. Signup and view all the answers

What does the magnetic quantum number indicate?

Symbolized by m, it indicates the orientation of an orbital around the nucleus. Signup and view all the answers

What is the spin quantum number?

The quantum number that has only two possible values, +1/2 and -1/2. Signup and view all the answers

What are subshells?

Orbitals with different shapes occupy different regions. Signup and view all the answers

What defines a nonpolar covalent bond?

Electronegativity is less than 0.5, and electrons are equally shared. Signup and view all the answers

What defines a polar covalent bond?

Electronegativity between 0.5 and 1.7; electrons are unequally shared. Signup and view all the answers

What defines an ionic bond?

Electronegativity greater than 1.7 between metal and nonmetal. Signup and view all the answers

Study Notes

Electron Configuration and Principles

Exceptions to the Aufbau principle arise from stability preferences in electron configurations, particularly in transition metals like copper and chromium.
Electron configuration refers to the distribution of electrons in an atom's orbitals.
The atom's electron arrangement is essential to understanding its chemical properties and reactivity.

Historical Periodic Table Arrangements

Initially, the periodic table was organized based on physical properties rather than atomic structure.
Johann Dobereiner classified elements into triads based on similar properties, like the halogen triad: chlorine, bromine, and iodine.
John Newlands introduced the Law of Octaves, suggesting that properties repeat every eighth element according to atomic mass.
Dmitri Mendeleev created a periodic table by increasing atomic mass, predicting undiscovered elements and their properties.

Key Figures in Periodic Table Development

Lothar Meyer produced a similar table to Mendeleev's around the same time.
Henry Moseley rearranged the periodic table by increasing atomic number, solidifying the modern organization.
Glenn T. Seaborg advanced the table by moving 14 elements to create the Actinide series and co-discovered ten new elements.

Structure of the Periodic Table

The periodic law states that the properties of elements are periodic functions of their atomic numbers.
Elements are arranged into rows (periods) and vertical columns (groups/families).
Chemical symbols are one or two-letter abbreviations derived from Greek or Latin names.

Atomic Characteristics

Atomic number indicates the number of protons or electrons in an atom.
The atomic mass is the sum of protons and neutrons in the nucleus.
Valence electrons are crucial for chemical bonding, with atoms typically having 1 to 8 in their outermost shell.

Trends in the Periodic Table

Atomic radius increases down a group due to the addition of energy levels, and decreases across a period due to increased nuclear charge.
Ionization energy, the energy required to remove an electron, is inversely proportional to atomic radius.
Electronegativity measures an atom's attraction for electrons; it increases left to right and decreases down a group.

Types of Elements

Most of the periodic table is made up of metals, which are typically shiny, malleable, ductile, and good conductors.
Nonmetals display opposite properties; they are dull, brittle, and poor conductors.
Metalloids possess characteristics of both metals and nonmetals, acting as semiconductors.

Chemical Bonds and Ion Formation

Atoms form ions through the gaining or losing of electrons, creating cations (positively charged) and anions (negatively charged).
Metallic character refers to how easily an atom can lose electrons, correlating with reactivity in metals and nonmetals.
The octet rule suggests that atoms strive for a full set of eight valence electrons for stability.

Quantum Mechanics and Electron Behavior

Quantum numbers describe electron positions, including principal energy levels, orbital shapes, orientations, and spins.
The Pauli Exclusion Principle allows a maximum of two electrons in an orbital with opposite spins, while Hund's Rule deals with the distribution of electrons among orbitals of the same energy.
Atomic orbitals have distinctive shapes: s orbitals are spherical, and p orbitals are dumbbell-shaped.

Bonding Types

Non-polar covalent bonds occur when electronegativity differences are less than 0.5, with electrons shared equally.
Polar covalent bonds arise from electronegativity differences between 0.5 and 1.7, resulting in unequal sharing of electrons.
Ionic bonds form when the electronegativity difference is greater than 1.7, typically between metals and nonmetals.

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Description

Explore the principles of electron configuration, including exceptions to the Aufbau principle, and the historical development of the periodic table. This quiz covers key figures and their contributions, such as Mendeleev and his predictions of undiscovered elements. Enhance your understanding of atomic structure and chemical properties.