Chemistry: Atoms and Elements

Flashcards covering key concepts related to atoms and elements, including atomic structure, isotopes, ions, and the periodic table.

What does the Greek word 'atomos' mean?

Indivisible

Who developed a theory that quantitatively explained Brownian motion?

Albert Einstein

What is the smallest identifiable unit of an element?

An atom

Who first proposed that matter was composed of small, indestructible particles?

Leucippus and Democritus

What is the law of conservation of mass?

In a chemical reaction, matter is neither created nor destroyed.

What does the law of definite proportions state?

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.

What does the law of multiple proportions state?

When two elements (A and B) form two different compounds, the masses of element B that combine with 1 gram of element A can be expressed as a ratio of small whole numbers.

Who conducted cathode ray experiments that led to the discovery of the electron?

J. J. Thomson

What did Robert Millikan deduce from his oil drop experiment?

The charge of a single electron

What is the plum-pudding model?

Negatively charged electrons were small particles held within a positively charged sphere.

Who performed the gold foil experiment?

Ernest Rutherford

What is the nuclear theory of the atom?

Most of the atom’s mass and all of its positive charge are contained in a small core called a nucleus; Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed; There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) within the nucleus, so that the atom is electrically neutral.

Who demonstrated that the previously unaccounted for mass was due to neutrons, neutral particles within the nucleus?

James Chadwick

What defines an element?

The number of protons in its nucleus

What are isotopes?

Atoms with the same number of protons but a different number of neutrons

What are ions?

Charged particles formed when atoms lose or gain electrons

What is a cation?

Positively charged ions

What is an anion?

Negatively charged ions

What is the periodic law?

When the elements are arranged in order of increasing mass, certain sets of properties recur periodically.

What are metalloids also classified as, due to their intermediate electrical conductivity?

Semiconductors

What are the group 8A elements called?

Noble gases

What are the group 1A elements also called?

Alkali metals

What are the group 2A elements also called?

Alkaline earth metals

What are the group 7A elements also called?

Halogens

What is the atomic mass?

The average mass of the isotopes that compose that element, weighted according to the natural abundance of each isotope.

What is a mole?

The measure of material containing 6.02214 x 10^23 particles

What is Avogadro's number?

6.02214 x 10^23

What is the molar mass?

The mass of 1 mole of atoms of an element