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D-head (clipped head) nail – a common or box nail with part of the head removed for some pneumatic nail guns; Double-ended nail – a rare type of nail with points on both ends and the "head" in the middle for joining boards together. See this patent. Similar to a dowel nail but with a head on the shank.
In thermodynamics, the particle number (symbol N) of a thermodynamic system is the number of constituent particles in that system. [1] The particle number is a fundamental thermodynamic property which is conjugate to the chemical potential. Unlike most physical quantities, the particle number is a dimensionless quantity, specifically a ...
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
One dalton is approximately the mass of one a single proton or neutron. [2] The unified atomic mass unit has a value of 1.660 538 921 (73) × 10 −27 kg. [3] The amu without the "unified" prefix is an obsolete unit based on oxygen, which was replaced in 1961.
The number density (symbol: n or ρ N) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density.
A pair of scales: An instrument for measuring mass in a force field by balancing forces. Balance; Check weigher measures precise weight of items in a conveyor line, rejecting underweight or overweight objects. Inertial balance; Katharometer; Mass spectrometers measure the mass-to-charge ratio, not the mass, of ionised particles. Weighing scale
One mole is an aggregate of exactly 6.022 140 76 × 10 23 elementary entities (approximately 602 sextillion or 602 billion times a trillion), which can be atoms, molecules, ions, ion pairs, or other particles. The number of particles in a mole is the Avogadro number (symbol N 0) and the numerical value of the Avogadro constant (symbol N A ...
The Avogadro constant, commonly denoted N A [1] or L, [2] is an SI defining constant with an exact value of 6.022 140 76 × 10 23 mol −1 (reciprocal moles). [3] [4] It is this defined number of constituent particles (usually molecules, atoms, ions, or ion pairs—in general, entities) per mole and used as a normalization factor in relating the amount of substance, n(X), in a sample of a ...