History of the Periodic Table

These flashcards cover key vocabulary related to the history and concepts of the periodic table as discussed in the lecture.

Dmitri Mendeleev

A chemistry professor who organized elements by atomic mass.

Atomic Mass

The mass of an atom that is used to organize elements in the periodic table.

Periodic Pattern

A cyclic or periodic pattern in the reactivity of elements.

Cross-classification

Organizing elements so that members of the same row and column share similarities.

Empty Spaces

Gaps left in Mendeleev's periodic table for undiscovered elements.

Eka-Aluminum

Name given by Mendeleev to Gallium before it was discovered.

Valence Electrons

Electrons that are in the outermost energy level of an atom.

Elements

Pure substances that cannot be broken down into simpler substances.

Reactivity

The tendency of a substance to undergo a chemical reaction.

Atomic Number

The number of protons in the nucleus of an atom.

Sodium

Element with atomic number 11 and symbol Na.

Gallium

Element with atomic number 31 and melting point of 29.78°C.

Hydrogen

The lightest and most abundant element in the universe.

Periodic Table

A chart that organizes all known elements by their properties.

Molar Mass

The mass of a given substance, in grams, divided by the amount of substance, in moles.

Chemical Symbol

An abbreviation for a chemical element, usually one or two letters.

Group

A vertical column in the periodic table, indicating elements with similar properties.

Period

A horizontal row in the periodic table, indicating elements with the same number of energy levels.

Cyclic Pattern

A repeating pattern observed in the periodic table based on atomic mass.

Diacidic Bases

Compounds that can yield two protons (H+) in solution.

Transition Metals

Elements found in groups 3 to 12 that have distinct properties.

Reactivity with Water

The ability of a substance to react with water to form new substances.

Mendeleev's Confidence

Mendeleev's assurance that the missing elements would eventually be discovered.

Boiling Point of Gallium

The temperature at which Gallium changes from a liquid to a gas, 2403°C.

Element Discovery Rate

In 1863, elements were being discovered at a rate of about one per year.

Periodicity

The repetitive pattern of chemical and physical properties of elements in the periodic table.

Electronegativity

The tendency of an atom to attract electrons towards itself.