Ancient Ideas
Heraclitus believed the fundamental substance was this element.
Fire
This scientist theorized that atomic masses were multiples of hydrogen, called protyles
William Prout
Lavoisier’s list of 33 elements included these two, which are today not regarded as atomic
Light, caloric
Group 2 elements are called this and are very reactive with a +2 charge.
Alkaline earth metals
These metals (Groups 3–12) are good conductors and malleable.
Transition metals
Anaximander proposed “apeiron,” meaning this boundless substance.
Infinite, boundless
This 19th-century chemist organized atomic masses in triads, a precursor to modern columns.
Johann Wolfgang Döbereiner
Moseley’s work confirmed each element has a unique integer that represents this subatomic particle.
Proton
The upper f-block elements are called this.
Lanthanides
Helium is a part of this group despite having two electrons in its valence shell
Noble gases
Aristotle added this fifth element for the fixed stars.
Aether
Henry Moseley rearranged the periodic table using this atomic property instead of mass.
Atomic number
Mendeleev used his Periodic Law to predict these about undiscovered elements.
Properties, atomic masses
Large groupings in the periodic table based on electron configuration are called this.
Block
Group 1 elements are called this and are highly reactive with a +1 charge.
Alkali metals
Thales, the first Greek philosopher, believed everything was made of this substance.
Water
He wrote the first modern chemistry textbook with a list of 33 elements.
Antoine Lavoisier
Prout’s Hypothesis claimed all elements are made of multiples of this particle.
Protyle
Döbereiner grouped elements into these sets.
Triads
A column in the periodic table is called this.
Group
These are the four classical elements proposed by Empedocles.
Fire, earth, water, air
This scientist measured atomic masses relative to hydrogen.
John Dalton
Mendeleev’s Periodic Law states properties repeat at certain intervals when elements are arranged by this.
Atomic mass
These group 17 elements are highly reactive, often with a -1 charge
Halogens
A row in the periodic table is called this.
Period