## Atomic Number of Bohrium

Bohrium is a chemical element with atomic number 107 which means there are 107 protons and 107 electrons in the atomic structure. The chemical symbol for Bohrium is Bh.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Bohrium

Atomic mass of Bohrium is 264 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Bohrium

Density of Bohrium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Bohrium – Properties Summary

Element Bohrium
Atomic Number 107
Symbol Bh
Element Category Transition Metal
Phase at STP Synthetic
Atomic Mass [amu] 264
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 6d5 7s2
Possible Oxidation States
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1976
Discoverer Scientists at Dubna, Russia
Thermal properties
Melting Point [Celsius scale]
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Hassium

Hassium is a chemical element with atomic number 108 which means there are 108 protons and 108 electrons in the atomic structure. The chemical symbol for Hassium is Hs.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Hassium

Atomic mass of Hassium is 277 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Hassium

Density of Hassium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Hassium – Properties Summary

Element Hassium
Atomic Number 108
Symbol Hs
Element Category Transition Metal
Phase at STP Synthetic
Atomic Mass [amu] 277
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 6d6 7s2
Possible Oxidation States
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1984
Discoverer Armbruster, Paula & Muenzenberg, Dr. Gottfried
Thermal properties
Melting Point [Celsius scale]
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Dubnium

Dubnium is a chemical element with atomic number 105 which means there are 105 protons and 105 electrons in the atomic structure. The chemical symbol for Dubnium is Db.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Dubnium

Atomic mass of Dubnium is 262 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Dubnium

Density of Dubnium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Dubnium – Properties Summary

Element Dubnium
Atomic Number 105
Symbol Db
Element Category Transition Metal
Phase at STP Synthetic
Atomic Mass [amu] 262
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 6d3 7s2
Possible Oxidation States
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1967
Discoverer Scientists at Dubna, Russia (1967)/Lawrence Berkeley Laboratory (1970)
Thermal properties
Melting Point [Celsius scale]
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Seaborgium

Seaborgium is a chemical element with atomic number 106 which means there are 106 protons and 106 electrons in the atomic structure. The chemical symbol for Seaborgium is Sg.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Seaborgium

Atomic mass of Seaborgium is 266 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Seaborgium

Density of Seaborgium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Seaborgium – Properties Summary

Element Seaborgium
Atomic Number 106
Symbol Sg
Element Category Transition Metal
Phase at STP Synthetic
Atomic Mass [amu] 266
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 6d4 7s2
Possible Oxidation States
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1974
Discoverer Albert Ghiorso et. al.
Thermal properties
Melting Point [Celsius scale]
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Lawrencium

Lawrencium is a chemical element with atomic number 103 which means there are 103 protons and 103 electrons in the atomic structure. The chemical symbol for Lawrencium is Lr.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Lawrencium

Atomic mass of Lawrencium is 262 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Lawrencium

Density of Lawrencium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Lawrencium – Properties Summary

Element Lawrencium
Atomic Number 103
Symbol Lr
Element Category Rare Earth Metal
Phase at STP Synthetic
Atomic Mass [amu] 262
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 7s2 7p1
Possible Oxidation States +3
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1961
Discoverer Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, Robert M. Latimer
Thermal properties
Melting Point [Celsius scale] 1627
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Rutherfordium

Rutherfordium is a chemical element with atomic number 104 which means there are 104 protons and 104 electrons in the atomic structure. The chemical symbol for Rutherfordium is Rf.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Rutherfordium

Atomic mass of Rutherfordium is 261 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Rutherfordium

Density of Rutherfordium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Rutherfordium – Properties Summary

Element Rutherfordium
Atomic Number 104
Symbol Rf
Element Category Transition Metal
Phase at STP Synthetic
Atomic Mass [amu] 261
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 6d2 7s2
Possible Oxidation States +4
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale]
1st Ionization Energy [eV]
Year of Discovery 1964
Discoverer Scientists at Dubna, Russia (1964)/Albert Ghiorso et. al. (1969)
Thermal properties
Melting Point [Celsius scale]
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Mendelevium

Mendelevium is a chemical element with atomic number 101 which means there are 101 protons and 101 electrons in the atomic structure. The chemical symbol for Mendelevium is Md.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Mendelevium

Atomic mass of Mendelevium is 258 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Mendelevium

Density of Mendelevium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Mendelevium – Properties Summary

Element Mendelevium
Atomic Number 101
Symbol Md
Element Category Rare Earth Metal
Phase at STP Synthetic
Atomic Mass [amu] 258
Density at STP [g/cm3]
Electron Configuration [Rn] 5f13 7s2
Possible Oxidation States +2,3
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale] 1.3
1st Ionization Energy [eV] 6.58
Year of Discovery 1955
Discoverer Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, Albert Ghiorso
Thermal properties
Melting Point [Celsius scale] 827
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Nobelium

Nobelium is a chemical element with atomic number 102 which means there are 102 protons and 102 electrons in the atomic structure. The chemical symbol for Nobelium is No.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Nobelium

Atomic mass of Nobelium is 259 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Nobelium

Density of Nobelium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Nobelium – Properties Summary

Element Nobelium
Atomic Number 102
Symbol No
Element Category Rare Earth Metal
Phase at STP Synthetic
Atomic Mass [amu] 259
Density at STP [g/cm3]
Electron Configuration [Rn] 5f14 7s2
Possible Oxidation States +2,3
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale] 1.3
1st Ionization Energy [eV] 6.65
Year of Discovery 1958
Discoverer Albert Ghiorso, Glenn T. Seaborg, Torbørn Sikkeland, John R. Walton
Thermal properties
Melting Point [Celsius scale] 827
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Fermium

Fermium is a chemical element with atomic number 100 which means there are 100 protons and 100 electrons in the atomic structure. The chemical symbol for Fermium is Fm.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Fermium

Atomic mass of Fermium is 257 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Fermium

Density of Fermium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Fermium – Properties Summary

Element Fermium
Atomic Number 100
Symbol Fm
Element Category Rare Earth Metal
Phase at STP Synthetic
Atomic Mass [amu] 257
Density at STP [g/cm3]
Electron Configuration [Rn] 5f12 7s2
Possible Oxidation States +3
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale] 1.3
1st Ionization Energy [eV] 6.5
Year of Discovery 1952
Discoverer Albert Ghiorso et. al.
Thermal properties
Melting Point [Celsius scale] 1527
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]

## Atomic Number of Einsteinium

Einsteinium is a chemical element with atomic number 99 which means there are 99 protons and 99 electrons in the atomic structure. The chemical symbol for Einsteinium is Es.

Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements.

How does the atomic number determine the chemical behavior of atoms?

## Atomic Mass of Einsteinium

Atomic mass of Einsteinium is 252 u.

Note that each element may contain more isotopes. Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance.

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 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.

The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element.

How does the atomic mass determine the density of materials?

## Density of Einsteinium

Density of Einsteinium is –g/cm3.

Typical densities of various substances at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

In other words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).

## Einsteinium – Properties Summary

Element Einsteinium
Atomic Number 99
Symbol Es
Element Category Rare Earth Metal
Phase at STP Synthetic
Atomic Mass [amu] 252
Density at STP [g/cm3]
Electron Configuration [Rn] 5f11 7s2
Possible Oxidation States +3
Electron Affinity [kJ/mol]
Electronegativity [Pauling scale] 1.3
1st Ionization Energy [eV] 6.42
Year of Discovery 1952
Discoverer Albert Ghiorso et. al.
Thermal properties
Melting Point [Celsius scale] 860
Boiling Point [Celsius scale]
Thermal Conductivity [W/m K]
Specific Heat [J/g K]
Heat of Fusion [kJ/mol]
Heat of Vaporization [kJ/mol]