# Meitnerium – Mass Number – Neutron Number – Mt

Meitnerium is a chemical element with atomic number 109 which means there are 109 protons and 109 electrons in the atomic structure. The chemical symbol for Meitnerium is Mt.

## Neutron Number and Mass Number of Meitnerium

Mass numbers of typical isotopes of Meitnerium are 274, 276, 278, 282.

The total number of neutrons in the nucleus of an atom is called the neutron number of the atom and is given the symbol N. Neutron number plus atomic number equals atomic mass number: N+Z=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.

Neutron number is rarely written explicitly in nuclide symbol notation, but appears as a subscript to the right of the element symbol. Nuclides that have the same neutron number but a different proton number are called isotones. The various species of atoms whose nuclei contain particular numbers of protons and neutrons are called nuclides. Each nuclide is denoted by chemical symbol of the element (this specifies Z) with tha atomic mass number as supescript. Therefore, we cannot determine the neutron number of uranium, for example. We can determine the neutron number of certain isotope. For example, the neutron number of uranium-238 is 238-92=146.

### Neutron and Mass Numbers and Nuclear Properties

Properties of atomic nuclei (atomic mass, nuclear cross-sections) are determined by the number of protons and number of neutrons (neutron number). It must be noted, especially nuclear cross-sections may vary by many orders from nuclide with the neutron number N to nuclide with the neutron number N+1. For example, actinides with odd neutron number are usually fissile (fissionable with slow neutrons) while actinides with even neutron number are usually not fissile (but are fissionable with fast neutrons). Heavy nuclei with an even number of protons and an even number of neutrons are (due to Pauli exclusion principle) very stable thanks to the occurrence of ‘paired spin’. On the other hand, nuclei with an odd number of protons and neutrons are mostly unstable.

### Neutron and Atomic Numbers and Nuclear Stability

Nuclear stability is a concept that helps to identify the stability of an isotope. To identify the stability of an isotope it is needed to find the ratio of neutrons to protons. To determine the stability of an isotope you can use the ratio neutron/proton (N/Z). Also to help understand this concept there is a chart of the nuclides, known as a Segre chart. This chart shows a plot of the known nuclides as a function of their atomic and neutron numbers. It can be observed from the chart that there are more neutrons than protons in nuclides with Z greater than about 20 (Calcium). These extra neutrons are necessary for stability of the heavier nuclei. The excess neutrons act somewhat like nuclear glue. Only two stable nuclides have fewer neutrons than protons: hydrogen-1 and helium-3.

Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electric force due to their positive charge. These two forces compete, leading to various stability of nuclei. There are only certain combinations of neutrons and protons, which forms stable nuclei.

Neutrons stabilize the nucleus, because they attract each other and protons , which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus. If there are too many or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoes radioactive decayUnstable isotopes decay through various radioactive decay pathways, most commonly alpha decaybeta decaygamma decay or electron capture. Many other rare types of decay, such as spontaneous fission or neutron emission are known.

## Atomic Mass of Meitnerium

Atomic mass of Meitnerium is 268 u.

The atomic mass is the mass of an atom. The atomic mass or relative isotopic mass refers to the mass of a single particle, and therefore is tied to a certain specific isotope of an element. The atomic mass is carried by the atomic nucleus, which occupies only about 10-12 of the total volume of the atom or less, but it contains all the positive charge and at least 99.95% of the total mass of the atom. Note that, each element may contain more isotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance.

The size and mass of atoms are so small that the use of normal measuring units, while possible, is often inconvenient. Units of measure have been defined for mass and energy on the atomic scale to make measurements more convenient to express. The unit of measure for mass is the atomic mass unit (amu). One atomic mass unit is equal to 1.66 x 10-24 grams. One unified atomic mass unit is approximately the mass of one nucleon (either a single proton or neutron) and is numerically equivalent to 1 g/mol.

For 12C the atomic mass is exactly 12u, since the atomic mass unit is defined from it. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. For example, 63Cu (29 protons and 34 neutrons) has a mass number of 63 and an isotopic mass in its nuclear ground state is 62.91367 u.

There are two reasons for the difference between mass number and isotopic mass, known as the mass defect:

1. The neutron is slightly heavier than the proton. This increases the mass of nuclei with more neutrons than protons relative to the atomic mass unit scale based on 12C with equal numbers of protons and neutrons.
2. The nuclear binding energy varies between nuclei. A nucleus with greater binding energy has a lower total energy, and therefore a lower mass according to Einstein’s mass-energy equivalence relation E = mc2. For 63Cu the atomic mass is less than 63 so this must be the dominant factor.

Note that, it was found the rest mass of an atomic nucleus is measurably smaller than the sum of the rest masses of its constituent protons, neutrons and electrons. Mass was no longer considered unchangeable in the closed system. The difference is a measure of the nuclear binding energy which holds the nucleus together. According to the Einstein relationship (E=mc2), this binding energy is proportional to this mass difference and it is known as the mass defect.

1
H

Hydrogen

Nonmetals

2
He

Helium

Noble gas

3
Li

Lithium

Alkali metal

4
Be

Beryllium

Alkaline earth metal

5
B

Boron

Metalloids

6
C

Carbon

Nonmetals

7
N

Nitrogen

Nonmetals

8
O

Oxygen

Nonmetals

9
F

Fluorine

Nonmetals

10
Ne

Neon

Noble gas

11
Na

Sodium

Alkali metal

12
Mg

Magnesium

Alkaline earth metal

13
Al

Aluminium

Post-transition metals

14
Si

Silicon

Metalloids

15
P

Phosphorus

Nonmetal

16
S

Sulfur

Nonmetal

17
Cl

Chlorine

Nonmetal

18
Ar

Argon

Noble gas

19
K

Potassium

Alkali metal

20
Ca

Calcium

Alkaline earth metal

21
Sc

Scandium

Transition metals

22
Ti

Titanium

Transition metals

23
V

Transition metals

24
Cr

Chromium

Transition metals

25
Mn

Manganese

Transition metals

26
Fe

Iron

Transition metals

27
Co

Cobalt

Transition metals

28
Ni

Nickel

Transition metals

29
Cu

Copper

Transition metals

30
Zn

Zinc

Transition metals

31
Ga

Gallium

Post-transition metals

32
Ge

Germanium

Metalloids

33
As

Arsenic

Metalloids

34
Se

Selenium

Nonmetal

35
Br

Bromine

Nonmetal

36
Kr

Krypton

Noble gas

37
Rb

Rubidium

Alkali metals

38
Sr

Strontium

Alkaline earth metals

39
Y

Yttrium

Transition metals

40
Zr

Zirconium

Transition metals

41
Nb

Niobium

Transition metals

42
Mo

Molybdenum

Transition metals

43
Tc

Technetium

Transition metals

44
Ru

Ruthenium

Transition metals

45
Rh

Rhodium

Transition metals

46
Pd

Transition metals

47
Ag

Silver

Transition metals

48
Cd

Transition metals

49
In

Indium

Post-transition metals

50
Sn

Tin

Post-transition metals

51
Sb

Antimony

Metalloids

52
Te

Tellurium

Metalloids

53
I

Iodine

Nonmetal

54
Xe

Xenon

Noble gas

55
Cs

Caesium

Alkali metals

56
Ba

Barium

Alkaline earth metals

57-71

Lanthanoids

72
Hf

Hafnium

Transition metals

73
Ta

Tantalum

Transition metals

74
W

Tungsten

Transition metals

75
Re

Rhenium

Transition metals

76
Os

Osmium

Transition metals

77
Ir

Iridium

Transition metals

78
Pt

Platinum

Transition metals

79
Au

Gold

Transition metals

80
Hg

Mercury

Transition metals

81
Tl

Thallium

Post-transition metals

82
Pb

Post-transition metals

83
Bi

Bismuth

Post-transition metals

84
Po

Polonium

Post-transition metals

85
At

Astatine

Metalloids

86
Rn

Noble gas

87
Fr

Francium

Alkali metal

88
Ra

Alkaline earth metal

89-103

Actinoids

104
Rf

Rutherfordium

Transition metal

105
Db

Dubnium

Transition metal

106
Sg

Seaborgium

Transition metal

107
Bh

Bohrium

Transition metal

108
Hs

Hassium

Transition metal

109
Mt

Meitnerium

110
Ds

111
Rg

Roentgenium

112
Cn

Copernicium

113
Nh

Nihonium

114
Fl

Flerovium

115
Mc

Moscovium

116
Lv

Livermorium

117
Ts

Tennessine

118
Og

Oganesson

57
La

Lanthanum

Lanthanoids

58
Ce

Cerium

Lanthanoids

59
Pr

Praseodymium

Lanthanoids

60
Nd

Neodymium

Lanthanoids

61
Pm

Promethium

Lanthanoids

62
Sm

Samarium

Lanthanoids

63
Eu

Europium

Lanthanoids

64
Gd

Lanthanoids

65
Tb

Terbium

Lanthanoids

66
Dy

Dysprosium

Lanthanoids

67
Ho

Holmium

Lanthanoids

68
Er

Erbium

Lanthanoids

69
Th

Thulium

Lanthanoids

70
Yb

Ytterbium

Lanthanoids

71
Lu

Lutetium

Lanthanoids

89
Ac

Actinium

Actinoids

90
Th

Thorium

Actinoids

91
Pa

Protactinium

Actinoids

92
U

Uranium

Actinoids

93
Np

Neptunium

Actinoids

94
Pu

Plutonium

Actinoids

95
Am

Americium

Actinoids

96
Cm

Curium

Actinoids

97
Bk

Berkelium

Actinoids

98
Cf

Californium

Actinoids

99
Es

Einsteinium

Actinoids

100
Fm

Fermium

Actinoids

101
Md

Mendelevium

Actinoids

102
No

Nobelium

Actinoids

103
Lr

Lawrencium

Actinoids