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.įor 12C, the atomic mass is exactly 12u since the atomic mass unit is defined from it. One atomic mass unit is equal to 1.66 x 10 -24 grams. The unit of measure for mass is the atomic mass unit (amu). Note that, each element may contain more isotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance. See also: Properties of Krypton Atomic Mass of Krypton Krypton – Properties Element Krypton Atomic Number 36 Symbol Kr Element Category Noble Gas Phase at STP Gas Atomic Mass 83.798 Density at STP 3.75 Electron Configuration 3d10 4s2 4p6 Possible Oxidation States 0 Electron Affinity - Electronegativity 3 1st Ionization Energy 13.9996 Year of Discovery 1898 Discoverer Ramsay, Sir William & Travers, Morris Thermal properties Melting Point -157.36 Boiling Point -153.22 Thermal Conductivity 0.00949 Specific Heat 0.248 Heat of Fusion 1.638 Heat of Vaporization 9.029 A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere and is often used with other rare gases in fluorescent lamps. Krypton is a member of group 18 (noble gases) elements.

The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.Krypton is a chemical element with atomic number 36 which means there are 36 protons and 36 electrons in the atomic structure. Chlorine most strongly attracts extra electrons.

Nonmetals like to gain electrons to form anions to have a fully stable electron shell. Nonmetals: Generally, nonmetals have more positive electron affinity than metals.Mercury most weakly attracts an extra electron. The electron affinity of metals is lower than that of nonmetals. Metals: Metals like to lose valence electrons to form cations to have a fully stable shell.Chlorine most strongly attracts extra electrons, while neon most weakly attracts an extra electron.Īffinities of Non metals vs. Atoms whose anions are more stable than neutral atoms have a greater affinity. Moreover, nonmetals have more positive affinity than metals. However, nitrogen, oxygen, and fluorine do not follow this trend. The electron affinities will become less negative as you go from the top to the bottom of the periodic table. Generally, the elements on the right side of the periodic table will have large negative electron affinity. Although affinity varies greatly across the periodic table, some patterns emerge. The greater the negative value, the more stable the anion is. This affinity is known as the second electron affinity and these energies are positive.Įlectron affinity can be either positive or negative value. However, more energy is required to add an electron to a negative ion which overwhelms any the release of energy from the electron attachment process. By convention, the negative sign shows a release of energy. This affinity is known as the first electron affinity and these energies are negative. When an electron is added to a neutral atom, energy is released. To use electron affinities properly, it is essential to keep track of sign. Kr + e – → Kr – – ∆H = Affinity = - kJ/mol Electron affinities are more difficult to measure than ionization energies.Īn atom of Krypton in the gas phase, for example, gives off energy when it gains an electron to form an ion of Krypton. Note that, ionization energies measure the tendency of a neutral atom to resist the loss of electrons. In other words, it can be expressed as the neutral atom’s likelihood of gaining an electron. The change in energy (in kJ/mole) of a neutral atom or molecule (in the gaseous phase) when an electron is added to the atom to form a negative ion. In chemistry and atomic physics, the electron affinity of an atom or molecule is defined as: Electron affinity of Krypton is - kJ/mol.

Krypton symbol