Chapter 2 - Atoms and Elements Flashcards
(59 cards)
The first people to propose that matter was composed of small, indestructible particles were _________ and his student __________.
Leucippus and his student Democritus.
_________ and __________ proposed that many different kinds of atoms existed, each different in shape and size, and that they moved randomly through empty space.
Leucippus and Democritus
What were the three most important laws that led to the development and acceptance of the atomic theory?
The law of conservation of mass, the law of definite proportions, and the law of multiple proportions.
State the law of conservation of mass.
“In a chemical reaction, matter is neither created nor destroyed.”
State the law of definite proportions.
- All samples of a given compound have the same proportions of their constituent elements.
- Compounds have definite proportions of their constituent elements because the atoms that compose them, each with its own specific mass, occur in a definite ratio.
- Since the ratio of atoms is the same for all samples of a particular compound, the ratio of masses is also the same.
In order for the results to be consistent with the law of ________ __________, the ratios must be the same for the two samples.
definite proportions
Who published the law of multiple proportions?
John Dalton.
State the law of multiple proportions.
- When two elements (A and B) form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.
- The masses of B that react with a fixed mass of A are always related to one another as small whole-number ratios.
State John Dalton’s first postulate on atomic theory.
- Each element is composed of small, indestructible particles called atoms.
State John Dalton’s second postulate on atomic theory.
- All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
- All atoms are unique.
State John Dalton’s third postulate on atomic theory.
- Atoms combine in simple, whole-number ratios to form compounds.
State John Dalton’s fourth postulate on atomic theory.
- Atoms of one element cannot change into atoms of another element.
- In a chemical reaction, atoms only change the way they are bound together with atoms.
Who discovered the electron?
J.J Thomson.
What was Robert Millikan’s famous experiment and what did he discover?
The oil drop experiment. He discovered the charge of a single electron.
The mass of an electron is about ____x lighter than hydrogen, the lightest atom.
2000x
The magnitude of the charge of the electron is of tremendous importance because…
it determines how strongly an atom holds its electrons.
Explain J.J Thomson’s Plum Pudding Model.
J.J Thomson proposed that the negatively charged electrons were small particles held within a positively charged sphere.
-Think of a blueberry muffin; the blueberries being the electrons and the rest of the muffin being the positively charged sphere.
__________ - the emission of small energetic particles from the core of certain unstable atoms.
Radioactivity
What are the three different types of radioactivity?
Alpha particles, beta particles, and gamma rays.
Ernest Rutherford, who had worked under ________ and subscribed to his plum pudding model, performed an experiment in order to confirm ________’s model.
Thompson
Ernest Rutherford is famous for his ____ _____ experiment
gold foil
Rutherford’s experiment, which employed _____ particles, proved it wrong instead.
alpha
In Rutherford’s experiment, if the gold atoms were indeed like blueberry muffins or plum pudding - with their mass and charge spread throughout the entire volume of the atom, these speeding probes would pass right through the gold foil with _______ deflection
minimum
Rutherford concluded that, in contrast to the plum-pudding model, matter must not be as uniform as it appears. It must contain large regions of empty space dotted with small regions of very dense _____.
matter
