The Periodic Table and Its History

A substance that cannot be broken down into simpler substances by chemical means.

Groups of three elements with similar properties, where the middle element's atomic weight is roughly the average of the other two.

Arrangement of elements where every 8th element has similar properties.

Arrangement of elements according to increasing atomic weight, where elements with similar properties appear at regular intervals (periodically).

The average mass of an atom of an element or isotope.

Irish chemist who gave a modern definition of an element.

English chemist who discovered elements using electricity.

Russian scientist who created a periodic table.

Elements arranged by increasing atomic weight exhibit repeating properties.

Number of protons in an atom's nucleus.

Properties of elements repeat periodically when arranged by increasing atomic number.

Elements ordered by increasing atomic number.

Sum of protons and neutrons in an atom's nucleus.

Represented by the letter "Z".

Represented by the letter "A".

Mass number minus atomic number equals the number of neutrons.

Atoms of the same element with the same atomic number but different mass numbers due to varying neutron counts.

The average mass of an element's isotopes, considering their natural abundance.

An instrument used to separate and identify isotopes, measure abundances, and determine relative atomic mass.

The process of converting atoms or molecules into ions by removing electrons.

Change of state from liquid to gas, occurring due to vacuum inside the spectrometer.

Increasing the speed of positive ions using charged plates inside the mass spectrometer

Charged particles in a magnetic field are deflected differently based on their masses, separating them.

A symbolic representation of the arrangement of electrons in different energy levels and sublevels within an atom. It describes which orbitals are occupied by electrons and how many electrons each orbital contains.

The rule that states that electrons are added to orbitals in order of increasing energy levels, starting with the lowest energy level.

Regions around the nucleus of an atom where electrons have specific energy levels. Higher energy levels are further from the nucleus.

Subdivisions of energy levels within an atom, identified by letters (s, p, d, f). Each sublevel consists of one or more orbitals.

Regions of space around the nucleus where an electron is most likely to be found. Each orbital can hold a maximum of two electrons.

Elements in the periodic table where the last electron added enters a d-orbital. They are located in groups 3-12.

The 4s sublevel is lower in energy than the 3d sublevel, so it is filled first according to the Aufbau principle. This is because the electrons in the 4s sublevel are closer to the nucleus and experience less shielding from other electrons.

The electronic configuration of Chromium (Cr) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵, where one 4s electron moves to the 3d orbital to achieve greater stability by having half-filled 3d orbitals and a half-filled 4s orbital.

The electronic configuration of Copper (Cu) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰, where one 4s electron moves to the 3d orbital to achieve greater stability by having a completely filled 3d orbital.

An atom that gains electrons becomes negatively charged, forming an anion. The number of gained electrons determines the ion's negative charge.

An atom that loses electrons becomes positively charged, forming a cation. The number of lost electrons determines the ion's positive charge.

Hund's Rule states that electrons individually occupy available orbitals of equal energy before pairing up within a subshell.

The Pauli Exclusion Principle states that no more than two electrons can occupy an orbital, and they must have opposite spins.

The periodic system is the arrangement of elements based on increasing atomic weight, where elements with similar properties recur periodically.

When elements are arranged in order of increasing atomic weight, their properties repeat or recur, creating periodic patterns. This is the basis of the periodic table.

Mendeleev switched their order because iodine's chemical properties (similar to chlorine and bromine) were more important than its atomic mass, which was lower than tellurium's.

They hadn't been discovered yet!

It eliminates the need to rearrange elements to fit their correct groups, making the periodic table more logical.

The fixed amount of energy an electron can have within an atom.

An orbit, according to Bohr, is a circular path an electron follows. An orbital is a region of space where there's a high probability of finding an electron, taking into account its wave properties.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸