Ch.2 Flashcards

(39 cards)

1
Q

Who were the early philosophers that discussed the basic structure of matter?

A

Leucippus and Democritus

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2
Q

What term did Leucippus and Democritus use to describe the smallest particles of matter?

A

atomos

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3
Q

What did Aristotle believe about the composition of matter?

A

Matter consisted of various combinations of the four elements: fire, earth, air, and water

This view dominated for over two thousand years

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4
Q

Who revolutionized chemistry with atomic theory in the early 19th century?

A

John Dalton

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5
Q

(Dalton Postulate 1) What is the smallest unit of an element that can participate in a chemical change?

A

Atom

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6
Q

(Dalton Postulate 2) Fill in the blank: An element consists of only one type of atom, which has a mass that is characteristic of the element and is the same for all _______.

A

atoms of that element

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7
Q

What does Dalton’s atomic theory state about compound’s ratios?

A

The number of atoms of each element are always present in the same ratio. Whole number ratio

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8
Q

What does Dalton’s atomic theory state (postulate 5) about atoms during a chemical change?

A

Atoms are neither created nor destroyed but are rearranged

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9
Q

What is the law of conservation of matter?

A

The total mass of matter remains constant during a chemical change

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10
Q

What does the law of definite proportions state?

A

All samples of a pure compound contain the same elements in the same proportion by mass

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11
Q

True or False: Samples that have the same mass ratio are necessarily the same substance.

A

False

Many compounds other than isooctane also have a carbon-to-hydrogen mass ratio of 5.33:1.00.

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12
Q

What is the law of multiple proportions?

A

When two elements react to form more than one compound, a fixed mass of one element reacts with masses of the other element in a ratio of small, whole numbers

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13
Q

What does this ratio demonstrate?

1.116 g Cl/1 g Cu – brown compound
(divided by)
0.558 g Cl/1 g Cu – green compound

= 2/1

A

The law of multiple proportions

The brown compound has twice the amount of chlorine per amount of copper as the green compound

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14
Q

What was physicist J.J. Thomson’s main experiment?

A

A cathode ray tube experiment investigating electrical discharges in low-pressure gases.

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15
Q

What did J.J. Thomson find in his cathode ray tube experiment?

A

Particles in the cathode ray were negatively charged, less massive than atoms, and fundamental subatomic constituents of all atoms. They are now called electrons.

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16
Q

What was Robert A. Millikan’s main experiment?

A

The oil drop experiment, where microscopic oil droplets were electrically charged and suspended using an electric field to determine the charge of a single electron.

17
Q

How did Millikan’s experiment confirm the charge of an electron?

A

The charge of an oil droplet was always a multiple of 1.6 × 10⁻¹⁹ C, meaning it must be the fundamental charge of a single electron.

18
Q

How was the mass of an electron determined?

A

Since Thomson had already found the charge-to-mass ratio (1.759 × 10¹¹ C/kg), and Millikan found the charge, the mass was calculated using a simple equation.

19
Q

What was J.J. Thomson’s model of the atom?

A

The “plum pudding” model (1904), which described a positively charged mass with electrons embedded in it.

20
Q

What was Ernest Rutherford’s experiment?

A

A beam of high-speed, positively charged alpha (α) particles was directed at a thin gold foil to observe how they scattered.

21
Q

What surprising result did Rutherford observe in his experiment?

A

Most α particles passed through the foil, but some were slightly deflected, and a few bounced almost straight back.

22
Q

How did Rutherford describe his unexpected findings?

A

He compared it to firing a 15-inch shell at a piece of tissue paper and having it bounce back.

23
Q

What did Rutherford conclude about the volume of an atom?

A

Most of the atom consists of empty space.

24
Q

What did Rutherford determine about the nucleus of an atom and why?

A

The nucleus is small, heavy, and positively charged because some α particles deflected sharply when they encountered its concentrated positive charge.

25
What is the nuclear model of the atom proposed by Rutherford?
An atom has a small, positively charged nucleus where most of its mass is concentrated, surrounded by negatively charged electrons.
26
What fundamental particle did Rutherford discover in atomic nuclei?
The proton, a positively charged subatomic particle.
27
What are isotopes?
Atoms of the same element that have different masses but are chemically identical. ## Footnote Discovered by Frederick Soddy. (Nobel prize for this in 1921)
28
What observation led to the discovery of isotopes?
Scientists found that some substances, like mesothorium, had different atomic masses but were chemically identical to known elements.
29
Who discovered the neutron, and when?
James Chadwick discovered the neutron in 1932.
30
What is a neutron?
A neutral subatomic particle with a mass approximately equal to that of a proton.
31
What is an anion?
A negatively charged atom. It has more electrons | Think emo anion (negative)
32
What is a cation?
A postively charged atom. It has fewer electrons | Think cation = cat and cats are positive
33
What is an ion?
A charged atom
34
What's the offical name for the attraction between opposites | "opposites attract"
Electrostatic attraction
35
How do you find the average atomic mass of an element?
Add up all the isotopes's mass (times % abundance). DONT DIVIDE!! | *Unless equal 50% 50% abundance
36
What are the properties of nonmetals?
Can be liquid, gas, or solids at room temperature; solids are brittle; nonconductors
37
What are the general properties of metalloids?
Shining solids (like metals), brittle (like nonmetals), semi conductors
38
What are the
39
Ionic compounds