Chemistry: Atoms and Elements

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

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28 Terms

1
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What does the Greek word 'atomos' mean?

Indivisible

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Who developed a theory that quantitatively explained Brownian motion?

Albert Einstein

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What is the smallest identifiable unit of an element?

An atom

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

Leucippus and Democritus

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What is the law of conservation of mass?

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

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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.

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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.

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

J. J. Thomson

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What did Robert Millikan deduce from his oil drop experiment?

The charge of a single electron

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What is the plum-pudding model?

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

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Who performed the gold foil experiment?

Ernest Rutherford

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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.

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

James Chadwick

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What defines an element?

The number of protons in its nucleus

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What are isotopes?

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

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What are ions?

Charged particles formed when atoms lose or gain electrons

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What is a cation?

Positively charged ions

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What is an anion?

Negatively charged ions

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What is the periodic law?

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

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

Semiconductors

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What are the group 8A elements called?

Noble gases

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What are the group 1A elements also called?

Alkali metals

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What are the group 2A elements also called?

Alkaline earth metals

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What are the group 7A elements also called?

Halogens

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What is the atomic mass?

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

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What is a mole?

The measure of material containing 6.02214 x 10^23 particles

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What is Avogadro's number?

6.02214 x 10^23

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What is the molar mass?

The mass of 1 mole of atoms of an element