Elements, Atomic Structure, Radioactivity, Electronic Structure of Atoms Flashcards Preview

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Flashcards in Elements, Atomic Structure, Radioactivity, Electronic Structure of Atoms Deck (156):
1

What do atoms consist of?

Three sub atomic particles and a dense nucleus

2

What are the three subatomic particles found in an atom?

Electron, neutron, proton

3

What is the relative charge of -
Proton
Neutron
Electron

P- +1
N- neutral
E- -1

4

What is the relative mass [amu] of-
Proton
Neutron
Electron

P-1
N-1
E-1/1838

5

What is the location within an atom of
Proton
Neutron
Electron

P- Nucleus
N- Nucleus
E- In energy levels orbiting the nucleus

6

Who discovered proton?

Rutherford

7

Who discovered neutron?

Chadwick

8

Who discovered the electron?

JJ Thomson

9

What do electrons occupy in an atom?

Definite energy levels orbiting the nucleus

10

Who discovered the existence of energy levels?

Niels Bohr

11

How did Niels Bohr find the existence of energy levels

He studied the emission spectra of hydrogen atoms that had been given energy and found a series of lines of specific energy, indicating that only specific energy jumps [absorbance and emissions] were possible in an atom

12

What provides strong evidence for the existence of energy levels within the atom?

Line spectra

13

What is the name given to the spectra of Paschen, Balmer, Lyman?

Electromagnetic spectrum

14

What region of the electromagnetic spectrum does Paschen lie?

Infrared [passion-red]

15

What region of the electromagnetic spectrum does Balmer lie?

Visible

16

What region of the electromagnetic spectrum does Lyman lie?

Ultraviolet

17

What is an energy level?

It’s the fixed amount of energy that an electron can have in an atom

18

Where do energy levels start in atom?

Closest to Nucleus

19

What formula did Neil’s Bohr produce to work out the maximum number of electrons that would fit each orbital?

2n^2

20

What are energy levels further divided into

Sublevels

21

What are sublevels?

Group of atomic orbitals, all of which have the same energy

22

What is an orbital?

A region in space where there is a high probability of finding electrons

23

What shape is an s orbital?

Spherical

24

What shape is the P orbital?

Dumbbell

25

Features of electrons

-occupy lowest available energy level
-fit max of two electrons in each sublevel
-wave-particle dualism
-not possible to determine the position and velocity of an electron at the same time

26

What causes the nuclear charge in an atom?

Protons

27

What is the atomic number?

It’s the number of protons in the nucleus of an atom

28

What does the atomic number tell you?

PEP
-position on periodic table
-number of electrons present
-number of protons

29

What is a mass number?

The sum of the number of protons and neutrons in the nucleus of an atom

30

What are isotopes?

Atoms of an element that contain the same number of protons but different number of neutrons and thus have different atomic masses

31

What is the relative atomic mass?

It’s the average mass of an atom of an element relative to one twelfth the mass of an atom of carbon-12

32

Why do we need a relative atomic mass?

In order to represent different varieties of isotopes and relative abundance’s

33

What is radioactivity?

It’s the spontaneous breaking up of unstable nuclei accompanied by the emission of radiation

34

What are the three different types of radiation?

Alpha particle, Beta particle, Gamma Ray

35

What is an alpha particle?

Helium nuclei with a positive charge and little penetrating ability

36

What is a beta particle?

Electrons with a negative charge and greater penetrating ability than alpha particles

37

What are gamma rays?

High energy electromagnetic radiation, with greater penetrating ability than beta particles

38

What stops penetrating power of an alpha particle?

A sheet of paper

39

What stops penetrating power of a beta particle?

5mm of aluminium

40

What stops penetrating power of an alpha particle?

Thick block of lead

41

Example of alpha particle and use

Americium-241
Smoke detectors

42

Example of beta particle and use

Carbon-14
Carbon dating [archaeology]

43

Example of gamma ray and use

Cobalt-60
Radiotherapy

44

What is the reason for the difference in mass numbers of isotopes?

Different number of neutrons

45

What did the ancient greeks propose?

All substances are composed of four elements - earth, air, water and fire

46

What did Robert Boyle propose?

Element definition
-an element is a substance that cannot be broken down into simpler substances by chemical means

47

What did John Dalton propose about the atom?

-atoms are tiny, indivisible, indestructible particles
-that are unique to each element

48

What did John Dalton propose about the element?

Elements combine to form compounds, they do so in fixed whole number ratios

49

What is the law of conservation of mass?

It states that matter is neither created nor destroyed in the course of a chemical reaction

50

What did Crookes discover?

Cathode rays
Maltese cross placed in path of rays, cast sharp shadow at end of discharge tube

51

What did Johnstone Stony propose?

Suggested a name for the negative particles [cathode rays] - electrons

52

How did JJ Thomson discover electron?

Showed cathode rays were negatively charged particles when attracted to positive plate in electric field

53

What did Thomson discover

Electron
Their charge to mass ratio

54

What did Henry Mosley discover?

Atomic number

55

How did Henry Mosley discover the atomic number?

Using X-rays, measured the number of positive charges [later called protons] in atoms and found the number was different for every element - unique

56

What was the significance of the discovery of the atomic number?

Confirmed Mendeleev’s positioning of some elements in periodic table

57

What did Millikan discover?

Measured change of electron accurately, conducting his oil drop experiment

58

What did Rutherford discover?

Nucleus and Proton

59

How did Rutherford discover the nucleus?

Bombarded gold foil with alpha particles

60

What was the result of the Geiger-marsden experiment?

-few were repelled back
-most pass straight through
-some were deflected at large angles

61

What was concluded from Geiger marsden experiment?

Atom consists mostly of space, with a dense positive nucleus

62

How was the proton discovered?

Rutherford bombarded atom’s nuclei and eventually pushed out positive particles known as protons

63

What did James Chadwick discover?

Neutron

64

How was the Neutron discovered?

Bombarded beryllium with alpha particles which caused neutral particles with same mass as protons to be pushed out

65

What did Niels Bohr discover?

The existence of energy levels, that electrons have fixed energies
Defined energy levels and 2n^2

66

What does the Heisenberg uncertainty principle state?

It is impossible to measure the velocity and position of an electron at the same time

67

What did Humphrey Davy discover?

Isolated new elements such as calcium and magnesium using electrochemical techniques

68

What did Dobereiner propose?

Law of triad -
Chemicals with similar properties were to be grouped in threes, the middle one having a mass midway between the other two
Discovered, Li, Na, K

69

What did Newlands propose?

Law of octaves
Chemical properties of every eight element were repeated

70

What did Mendeleev propose?

Periodic table
Arranged elements known and unknown in periodic lines according to increasing atomic weight

71

What did Becquerel discover?

Spontaneous radioactive emissions

72

What did Marie Curie discover?

Isolated two highly radioactive elements -polonium and radium

73

Who coined the term “radioactivity”

Marie Curie

74

What substance was used to discover polonium and radium?

Purified Pitchblende

75

What substance was used to discover spontaneous radioactive emissions?

Uranium salts

76

What were the features of elements in a triad?

-similar chemical properties
-atomic weight of the middle elements would be midway between the other two

77

What was the law of triads limitation?

Restricted to only a small number of elements

78

What link made by dobereiner was essentially important in drawing up periodic table?

Link between different elements depended upon atomic weights

79

Limitations of the law of octaves

-tried to force all known elements to fit pattern and fitted very reactive metals in the same group as unreactive metals
-only worked for a small number of elements

80

What relationship was made in the periodic table?

Properties of elements and their atomic weights

81

Differences between Mendeleev’s periodic table and the Modern Periodic table

Mendeleev -
gaps left for undiscovered elements
in order of increasing atomic weight
Modern -
gaps filled
in order of increasing atomic number

82

What property of cathode rays allowed Thomson to measure charge to mass ratio

They are deflected by magnetic fields

83

Describe Thompson’s plum pudding model

Atoms were positive spheres in which negatively charged electrons were embedded

84

Who disproved plum pudding model?

Rutherford
instead - mostly made up of empty space with positive dense nucleus, electrons orbiting nucleus

85

What was the Bohr Model of the Atom?

Electrons were arranged in a series of concentric circular orbits at an increasing distance from the nucleus

86

Name the series of coloured lines in the line emission spectrum of hydrogen corresponding to transitions of electrons from higher energy levels to the second n=2 energy level

Balmer series

87

Name the series of coloured lines in the line emission spectrum of hydrogen corresponding to transitions of electrons from n=3 to n=1

Ultraviolet region

88

Give an example of a radioactive isotope and state one common use made of this isotope?

Americium -241 [smoke alarms]
Carbon -14 [archaeological dating]
Cobalt-60 [radiotherapy]

89

What is used to calculate the relative atomic mass of an element?

Mass spectrometer

90

What is the principle of the mass spectrometer?

Positive charged ions are separated on the basis of their relative masses moving in a magnetic field

91

What are the five processes in mass spectrometry?

-vaporisation
-ionisation
-acceleration
-separation
-detection

92

Give a use of mass spectrometry

Drug tests

93

Explain what occurs in vaporisation in mass spectrometry

Sample becomes heated and turns into a gas

94

Explain what occurs in ionisation in mass spectrometry

High energy electrons are shot at sample which knocks out an electron to form a positive ion

95

Explain what occurs in acceleration in mass spectrometry

Passes through an electric field to accelerate positive ions to high speed

96

Explain what occurs in separation in mass spectrometry

Pass through magnetic field and are deflected : lighter ions are deflected more than heavier ions. in this way, particles with different masses can be separates and identified

97

Explain what occurs in detection in mass spectrometry

ions are detected

98

What instrument was fundamental in detecting the existence of isotopes?

Mass spectrometer

99

What is the difference between a nuclear reaction and a chemical reaction?

Chemical - changes in distribution of electrons, cannot change one element into another element
Nuclear - changes in nucleus and can cause elements to change into other elements

100

What is a radioisotope?

Unstable, radioactive isotopes

101

What is the half-life of a radioactive isotope?

It’s the time taken for half of the atoms in a sample of the isotope to decay

102

What gas makes up more than half of the background radiation?

Radon gas

103

What are we told from carrying out the flame test

Each metal has their own characteristic colour, therefore the colours obtained can be used to identify the metals present in unknown compounds

104

Why is the line spectrum of each element unique?

The spacing between energy levels in terms of energy are also unique in atoms of that element

105

What colour does barium turn in flame tests?

Green

106

What colour does copper turn in flame tests?

Blue-green

107

What colour does lithium turn in flame tests?

Deep red

108

What colour does potassium turn in flame tests?

Lilac

109

What colour does sodium turn in flame tests?

Yellow

110

What colour does strontium turn in flame tests?

Red

111

Procedure for flame tests

-using a soak wooden splint
-crush a little bit of the salt to be tested using mortar and pestle
-dip wooden splint in salt and put over Bunsen flame and note the characteristic colour given off
-repeat the experiment with other salts

112

Why is the emission spectra useful in identifying an element?

The emission spectrum of an element is characteristic of that element

113

What is the ground state?

The lowest energy state

114

What is the excited state?

A higher energy state

115

What occurs when energy is emitted in an atom?

Electron moves from a higher energy level to a lower energy level

116

Under normal circumstances, where is the hydrogen electron found?

The ground stage

117

What occurs if an electron receives enough energy?

It will move to an excited state [here it’s relatively unstable]

118

Why does the electron in the hydrogen often atom eventually fall back down?

It is unstable in the excited state, therefore drops back down emitting energy

119

What is the aufbau principle?

States that electrons will occupy the lowest energy sublevel available

120

What is the atomic radius of an element?

It is half the distance between the nuclei of two atoms of the element that are joined together by a single covalent bond

121

Describe and account for the trend in atomic radii of the elements across the second period

Decreases
Increase in Nuclear charge - exerts a greater attractive force on the outer electrons
No screening effect - electrons are held closer and therefore radius is smaller

122

Describe and account for the trend in atomic radii of the elements going down a group

Increases
Addition of extra energy levels -increase in number of filled shells
Screening effect - electrons in inner shells partially neutralise the nuclear charge by repelling the outer electron

123

What is first ionisation energy

It’s the energy required to remove the most loosely bound electron from an isolated atom in its ground state

124

What is the equation of first ionisation energy?

X -> X^+ + e^-

125

What is the first ionisation energy measured in?

KJ per mole

126

Describe and account for the trend in first ionisation energy of the elements across period

General increase -
Increase in nuclear charge which holds the electrons more tightly making them difficult to remove
Decrease in atomic radius holds electrons in more tightly and also make them difficult to remove
No screening effect

127

Describe and account for the trend in first ionisation energy of the elements going down a group

Decrease
Increase in atomic radius makes it easier to remove an electron despite the increased nuclear charge
Screening effect of inner levels - electrons in inner shells partially neutralise the nuclear charge by repelling the outer electron

128

Account for the decrease in first ionisation energy between nitrogen and oxygen
[write out electronic configuration]

Nitrogen is more stable due to its half filled 3p orbital
Oxygen has a pair of electrons in px sublevel. If electron was taken away it would be stable.

129

Explain why the second ionisation energy of sodium is significantly higher than the first while the increase in the second ionisation energy or Neon compared to its first is relatively small
[write out electronic configuration]

Na = 1st electron removed is from the third shell which gives sodium a high stability configuration, but loss of second is from high stability atom, higher
Ne = both electrons are removed from same sublevel

130

Peaks in trend table
Explain :
High peaks, low peaks and medium peaks
[draw electronic configuration]

The high peaks - represent already stable atoms with filled p sublevel
Medium peaks - half filled sub levels or filled sublevels
Low troughs - atoms happy to have electrons removed due to unstable electronic configuration

HIGH = STABLE
LOW = UNSTABLE

131

What is the second ionisation energy?

Minimum energy required to remove the most loosely bound electron from each monopositive ion in a mole of these ions

132

How is the second ionisation energy represented in an equation?

X^+ -> X2+ + e^-

133

How does the definition of second ionisation energy differ from that of first ionisation energy?

The electron is removed from each monopositive ion

134

Evidence supporting Bohr Theory

-ionisation energy always rises due to protons in the nucleus pulling on less and less electrons causing a decrease in the radius of an atom
-energy jumps = small differences between ionisation energies for electrons belonging to the same shell but large differences of electrons are removed from different shells

135

Bohrs limitations

-only worked for hydrogen
-did not take into account of wave-particle duality
-did not take into account Heisenberg’s uncertainty principle
-didn’t include the discovery of sublevels

136

Features of transition metals

High densities
High boiling /meltingpoints

137

Calculate the mass of sodium chloride required to prepare 500cm^3 of a .9% w/v saline solution

G/500 =.9
G= 500(.9)
G= 450
450/100 - 4-5 g
[per 100cm^3]

138

M^2+ has 25 electrons and 32 neutrons
What is the atomic number and the mass number?

Atomic number [protons] - 27
Mass number [protons and neutrons] - 59

139

How many electrons and neutrons has the aluminium ion
27
13 Al ^3+

Electrons [-3] - 13-3 = 10
Neutrons - 27-13 = 14

140

Explain why relative atomic masses are rarely whole numbers

Average of mass numbers of isotopes of an element

141

What changes take place in the nucleus of an atom when beta decay occurs?

Neutron changes into proton
Electron emitted

142

When 19.05g of copper reacted with nitrogen, 20.45g of copper nitride.
Deduce the empirical formula of copper nitride

Cu3N
19.05/64 - .3
20.45-19.05 = 1.4/78 = .1
3:1

143

Find the empirical formula of a compound containing 40% sulfur and 60% oxygen, by mass

40/32 - 1.25
60/16 - 3.75
1:3
SO3

144

Calculate the daly mass of potassium iodide needed to supply .15mg of iodide ion

.15/127 - .00118
.00118 x 166 - .196

145

How many neutrons are there in
.14g of carbon 14

.14/14 - .01
.01 x 6 x 10^23 x 8 NEUTRONS =
4.8 x10^22

146

When hydrogen gas was passed over 1.59g of copper oxide, 1.27g of metallic copper were produced. Find by calculation the empirical formula of the copper oxide

1.59 - 1.27 = .32
1.27/64 = .02
.32/16 = .02

147

Complete and balance the equation for the chemical reaction that occurs when sodium is added to ethanol
C2H5OH + Na ->

C2H5OH + Na -> C2H5ONa + 1/2 H2

148

State the number of sublevels and orbitals in an argon atom (atomic no : 18)

1s2,2s2,2p6,3s2,3p6
Sublevels - 5 (s,s,p,s,p)
Orbitals - 9 (s,s,px,py,pz,s,px,py,pz)

149

Write a balanced nuclear equation for the beta particle decay of iodine-131 (atomic no - 53)

53 -1
131 I -> 0 é + Xe

150

Give two properties of cathode rays

Positively charged
Negligible mass
Travel in straight lines

151

Write the electron configuration of the oxygen (oxide) ion O2-

1s2,2s2,2p6

152

How many atoms of iron are there in a 30g bowl of cornflakes that contains .0024g of iron per 30g serving

.0024/mr(56) = 4.29 x 10-5 x 6 x 10^23 = 2.6 x 10^19

153

How many iron atoms should be consumed daily to meet the recommended daily intake of iron in a diet of 0.014g

.014 / 56 = .00025 x 6 x10^23 = 1.5 x 10^20

154

A 500cm^3 can of beer contains 21.5cm^3 of ethanol. Calculate its % alcohol

21.5/500 x 100/1 = 4.3%

155

Name the scientist who identified cathode rays as subatomic particles

JJ. Thomson

156

Calculate the percentage carbon, by mass, in methylbenzene

Carbon (mr of 12) - 7 carbons x 12 = 84
Hydrogen (mr of 1) = 8 hydrogens x 1 = 8
84/84+8 x100/1 = 91.3%