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: The Standard English unit is pounds mass per cubic foot ( lbm/ft 3).Įlectron Affinity and Electronegativity of SodiumĮlectron Affinity of Sodium is 52.8 kJ/mol. The standard SI unit is kilograms per cubic meter ( kg/m 3). 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. It is an intensive property, which is mathematically defined as mass divided by volume:

Typical densities of various substances at atmospheric pressure.ĭensity is defined as the mass per unit volume. For 63Cu, the atomic mass is less than 63, so this must be the dominant factor. A nucleus with greater binding energy has lower total energy, and therefore a lower mass according to Einstein’s mass-energy equivalence relation E = mc 2. The nuclear binding energy varies between nuclei.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. The neutron is slightly heavier than the proton.There are two reasons for the difference between mass number and isotopic mass, known as the mass defect: 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. The isotopic mass usually differs for other isotopes and is usually within 0.1 u of the mass number. 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 Sodium Atomic Mass of Sodium Sodium – Properties Element Sodium Atomic Number 11 Symbol Na Element Category Alkali Metal Phase at STP Solid Atomic Mass 22.9897 Density at STP 0.968 Electron Configuration 3s1 Possible Oxidation States +1 Electron Affinity 52.8 Electronegativity 0.93 1st Ionization Energy 5.1391 Year of Discovery 1807 Discoverer Davy, Sir Humphry Thermal properties Melting Point 97.8 Boiling Point 883 Thermal Conductivity 141 Specific Heat 1.23 Heat of Fusion 2.598 Heat of Vaporization 96.96 Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged atom-the Na+ cation. Sodium is a soft, silvery-white, highly reactive metal. Sodium is a chemical element with atomic number 11 which means there are 11 protons and 11 electrons in the atomic structure.

Sodium atom