Ch 3 Section 3 Flashcards Preview

Chem > Ch 3 Section 3 > Flashcards

Flashcards in Ch 3 Section 3 Deck (74):
1

Atoms are much too small to be

Measured individually

2

Chemists can analyze atoms

Quantitatively by knowing fundamental properties of the atoms of each element

3

Mole

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

4

All atoms are composed of the

Same basic particles

5

Atoms of different elements have

Different numbers of protons

6

Atoms of the same element all have the same number of

Protons

7

The atomic number (Z) of an element is

The number of protons of each atom of that element

8

All atoms of the element hydrogen have

One proton

9

The atomic number identifies

An element

10

The simplest atoms are those of

Hydrogen

11

Like many naturally occurring elements hydrogen atoms can have

Different numbers of neutrons

12

The most common type of hydrogen is sometimes called

Protium

13

Protium accounts for

99.9885% of the hydrogen atoms found on earth

14

The nucleus of a protium atom consists of

One proton only and it had one electron moving about it

15

Another form of hydrogen is deuterium which accounts for

0.0115% of earths hydrogen atoms

16

Each deuterium atom has a

Nucleus with one proton and one neutron

17

The third form of hydrogen is known as tritium which is

Radioactive

18

Tritium exists in very small

Amounts in nature but can be prepared artificially

19

Each tritium atom has one

Proton, two neutrons, and one electron

20

Isotopes are atoms of the same element that have

Different masses

21

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

Protons and electrons but different numbers of neutrons

22

Most of the elements consist of

Mixtures of isotopes

23

Identifying an isotope requested knowing both the

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

24

The mass number is the

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

25

Isotopes are usually identified by

Specifying their mass number

26

There are two methods for

Specifying isotopes

27

In the first method the mass number is written with a

Hyphen after the name of the element (hyphen notation)

28

The second method shows the composition of a

Nucleus using the isotopes nuclear symbol

29

The superscript in nuclear symbol indicates the

Mass number (protons + neutrons)

30

The subscript in nuclear symbol indicates the

Atomic number (number of protons)

31

The number of neutrons is found by

Subtracting the atomic number from the mass number

32

Nuclide is a general term for a

Specific isotope of an element

33

Masses of atoms expressed in grams are

Very small

34

For most chemical calculations it is more convenient to use

Relative atomic masses

35

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

Arbitrarily chosen as the standard and assigned a mass value

36

The masses of all other atoms are expressed in

Relation to this defined standard

37

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

Carbon-12 atom

38

One atomic mass unit or 1 amu

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

39

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

Carbon-12 atom

40

Isotopes of an element may occur naturally or they may be

Made in the laboratory (artificial isotopes)

41

Although isotopes have different masses they do not

Differ significantly in their chemical behavior

42

The masses of subatomic particles can also be expressed in the

Atomic mass scale

43

The mass of the electron is

0.000 5486 amu

44

The mass of the proton is

1.007 276 amu

45

The mass of a neutron is

1.008 665 amu.

46

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

Quite close to each other

47

Mass number and relative atomic mass are not identical because the

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

48

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

Nucleus from its protons and neutrons

49

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

Nearly always the same no matter where the element is found

50

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

Calculating the elements average atomic mass

51

Average atomic mass is the

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

52

The average atomic mass of an element depends on both the

Mass and the relative abundance of each of the elements isotopes

53

The average atomic mass of copper can be calculated by

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

54

Most atomic masses are known to

Four or more significant figures

55

The relative atomic mass scale makes it possible to know

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

56

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

The basis for relating masses in grams to numbers of atoms

57

A mole is the amount of a

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

58

The mole is a

Counting unit

59

The number of particles in a mole has been

Experimentally determined in a number of ways

60

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

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

61

The number of particles in a mole is known as

Avogadro's number

62

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

Crucial in explaining the relationship between mass and numbers of atoms

63

Avogadro's number is the number of

Particles in exactly one mole of a pure substance

64

For most purposes Avogadro's number is rounded to

6.022 x 10^23

65

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

Avogadro's number of particles

66

The molar mass of a substance is the

Mass of one mole of a pure substance

67

Molar mass is usually written in units of

g/ mol

68

The molar mass of an element is numerically equal to the

Atomic mass of the element in atomic mass u to

69

The molar mass of an element contains

One mole of atoms

70

Chemists use molar mass as a

Conversion factor in chemical calculations

71

Avogadro's number can be used to find the

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

Such problems are useful in demonstrating the

Meaning of Avogadro's number

73

In these calculations Avogadro's number is expressed in

Units of atoms per mole

74

Neon is a

Minor component of the atmosphere