Chemistry Unit 3 - Electron Config.

Who developed the first periodic table and what was it based on?

Dimitri Mendeleev developed the first periodic table based on atomic mass and periodic trends in properties.

How did Henry Moseley revise Mendeleev's periodic table?

Henry Moseley arranged the elements according to their atomic number.

What do vertical columns in the periodic table represent?

Vertical columns, called groups, represent elements that share similar valence electron configurations.

What is the key characteristic of Alkali metals in Group 1?

Alkali metals are reactive and have one valence electron.

What is the difference between metals and nonmetals?

Metals are good conductors, shiny, and malleable; nonmetals are poor conductors and brittle.

Describe the Bohr model of atomic structure.

The Bohr model describes electrons orbiting the nucleus in fixed, circular paths.

What limitation does the Bohr model have?

It is primarily accurate for hydrogen and fails for heavier elements.

What does the wave mechanical model state about electron paths?

Electrons occupy orbitals, which are three-dimensional regions of space, rather than following fixed orbits.

What is the Aufbau principle in electron configuration?

The Aufbau principle states that electrons fill the lowest energy levels and orbitals first.

What does the Pauli Exclusion Principle dictate?

It states that each orbital can hold a maximum of two electrons with opposite spins.

What is the significance of Hund's Rule?

Hund's Rule states that within a sublevel, each orbital must contain one electron first before pairing.

In electron configuration, what does the term 'core electrons' refer to?

Core electrons are the inner electrons that are not involved in chemical bonding.

What is the Octet Rule?

Atoms strive to achieve a full valence shell, typically with 8 valence electrons, for stability.

What is an isoelectronic species?

Isoelectronic species are atoms or ions that have the same electron configuration.

Give an example of an isoelectronic pair.

Oxygen ion (O²⁻) and Neon (Ne) are isoelectronic as both have the electron configuration 1s² 2s² 2p⁶.