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Chem > Ch 3 Section 3 > Flashcards

Ch 3 Section 3 Flashcards

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1
Q

Atoms are much too small to be

A

Measured individually

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2
Q

Chemists can analyze atoms

A

Quantitatively by knowing fundamental properties of the atoms of each element

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3
Q

Mole

A

A special unit used by chemists to express amounts of particles, such as atoms and molecules

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4
Q

All atoms are composed of the

A

Same basic particles

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5
Q

Atoms of different elements have

A

Different numbers of protons

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6
Q

Atoms of the same element all have the same number of

A

Protons

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7
Q

The atomic number (Z) of an element is

A

The number of protons of each atom of that element

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8
Q

All atoms of the element hydrogen have

A

One proton

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9
Q

The atomic number identifies

A

An element

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10
Q

The simplest atoms are those of

A

Hydrogen

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11
Q

Like many naturally occurring elements hydrogen atoms can have

A

Different numbers of neutrons

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12
Q

The most common type of hydrogen is sometimes called

A

Protium

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13
Q

Protium accounts for

A

99.9885% of the hydrogen atoms found on earth

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14
Q

The nucleus of a protium atom consists of

A

One proton only and it had one electron moving about it

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15
Q

Another form of hydrogen is deuterium which accounts for

A

0.0115% of earths hydrogen atoms

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16
Q

Each deuterium atom has a

A

Nucleus with one proton and one neutron

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17
Q

The third form of hydrogen is known as tritium which is

A

Radioactive

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18
Q

Tritium exists in very small

A

Amounts in nature but can be prepared artificially

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19
Q

Each tritium atom has one

A

Proton, two neutrons, and one electron

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20
Q

Isotopes are atoms of the same element that have

A

Different masses

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21
Q

The isotopes of a particular element all have the same number of

A

Protons and electrons but different numbers of neutrons

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22
Q

Most of the elements consist of

A

Mixtures of isotopes

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23
Q

Identifying an isotope requested knowing both the

A

Name or atomic number of the element and the mass of the isotope

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24
Q

The mass number is the

A

Total number of protons and neutrons that make up the nucleus of an isotope

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25
Q

Isotopes are usually identified by

A

Specifying their mass number

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26
Q

There are two methods for

A

Specifying isotopes

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27
Q

In the first method the mass number is written with a

A

Hyphen after the name of the element (hyphen notation)

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28
Q

The second method shows the composition of a

A

Nucleus using the isotopes nuclear symbol

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29
Q

The superscript in nuclear symbol indicates the

A

Mass number (protons + neutrons)

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30
Q

The subscript in nuclear symbol indicates the

A

Atomic number (number of protons)

31
Q

The number of neutrons is found by

A

Subtracting the atomic number from the mass number

32
Q

Nuclide is a general term for a

A

Specific isotope of an element

33
Q

Masses of atoms expressed in grams are

A

Very small

34
Q

For most chemical calculations it is more convenient to use

A

Relative atomic masses

35
Q

In order to set up a relative scale of atomic mass one atom has been

A

Arbitrarily chosen as the standard and assigned a mass value

36
Q

The masses of all other atoms are expressed in

A

Relation to this defined standard

37
Q

The standard used by scientists to compare units of atomic mass is the

A

Carbon-12 atom

38
Q

One atomic mass unit or 1 amu

A

Is exactly 1/12 the mass of a carbon-12 atom

39
Q

The atomic mass of any other atom is determined by comparing it with the mass of the

A

Carbon-12 atom

40
Q

Isotopes of an element may occur naturally or they may be

A

Made in the laboratory (artificial isotopes)

41
Q

Although isotopes have different masses they do not

A

Differ significantly in their chemical behavior

42
Q

The masses of subatomic particles can also be expressed in the

A

Atomic mass scale

43
Q

The mass of the electron is

A

0.000 5486 amu

44
Q

The mass of the proton is

A

1.007 276 amu

45
Q

The mass of a neutron is

A

1.008 665 amu.

46
Q

The mass number and relative atomic mass of a given nuclide are

A

Quite close to each other

47
Q

Mass number and relative atomic mass are not identical because the

A

Proton and neutron masses deviate slightly from 1 amu and the atomic masses include electrons

48
Q

A small amount of mass is changed to energy in the creation of a

A

Nucleus from its protons and neutrons

49
Q

The percentage of each isotope in the naturally occurring element on earth is

A

Nearly always the same no matter where the element is found

50
Q

The percentage at which each of an elements isotopes occurs in nature is taken into account when

A

Calculating the elements average atomic mass

51
Q

Average atomic mass is the

A

Weighted average of the atomic masses of the naturally occurring isotopes of an element

52
Q

The average atomic mass of an element depends on both the

A

Mass and the relative abundance of each of the elements isotopes

53
Q

The average atomic mass of copper can be calculated by

A

Multiplying the atomic mass of each isotope by its relative abundance (in decimal form) and adding the results

54
Q

Most atomic masses are known to

A

Four or more significant figures

55
Q

The relative atomic mass scale makes it possible to know

A

How many atoms of an element are present in a sample of the element with a measurable mass

56
Q

Three very important concepts- mole, Avogadro’s number, and molar mass- provide

A

The basis for relating masses in grams to numbers of atoms

57
Q

A mole is the amount of a

A

Substance that contains as many particles as there are atoms in exactly 12 g of carbon-12

58
Q

The mole is a

A

Counting unit

59
Q

The number of particles in a mole has been

A

Experimentally determined in a number of ways

60
Q

The best modern value for the number of particles in a mole is

A

6.022 141 79 x 10^23 which means that exactly 12 g of carbon contains that number of carbon-12 atoms

61
Q

The number of particles in a mole is known as

A

Avogadro’s number

62
Q

Avogadro’s number is named for the 19th century Italian scientist whose ideas were

A

Crucial in explaining the relationship between mass and numbers of atoms

63
Q

Avogadro’s number is the number of

A

Particles in exactly one mole of a pure substance

64
Q

For most purposes Avogadro’s number is rounded to

A

6.022 x 10^23

65
Q

An alternative definition of mole is the amount of a substance that cot subs

A

Avogadro’s number of particles

66
Q

The molar mass of a substance is the

A

Mass of one mole of a pure substance

67
Q

Molar mass is usually written in units of

A

g/ mol

68
Q

The molar mass of an element is numerically equal to the

A

Atomic mass of the element in atomic mass u to

69
Q

The molar mass of an element contains

A

One mole of atoms

70
Q

Chemists use molar mass as a

A

Conversion factor in chemical calculations

71
Q

Avogadro’s number can be used to find the

A

Number of atoms of an element from the amount in moles or to find the amount of an element in miles from the number of atoms

72
Q

Such problems are useful in demonstrating the

A

Meaning of Avogadro’s number

73
Q

In these calculations Avogadro’s number is expressed in

A

Units of atoms per mole

74
Q

Neon is a

A

Minor component of the atmosphere

Chem (54 decks)

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