![]() ![]() ![]() Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.įor stable elements, there is usually a variety of stable isotopes. Neutron number plus atomic number equals atomic mass number: N+Z=A. 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. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10 -19 coulombs. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The Standard English unit is pounds mass per cubic foot ( lbm/ft 3).Ĭhlorine – Properties Summary Element Chlorine Atomic Number 17 Symbol Cl Element Category Halogen Phase at STP Gas Atomic Mass 35.453 Density at STP 3.214 Electron Configuration 3s2 3p5 Possible Oxidation States +1,5,7/-1 Electron Affinity 349 Electronegativity 3.16 1st Ionization Energy 12.9676 Year of Discovery 1774 Discoverer Scheele, Carl Wilhelm Thermal properties Melting Point -101 Boiling Point -34.6 Thermal Conductivity 0.0089 Specific Heat 0.48 Heat of Fusion 3.23 Heat of Vaporization 10.Atomic Number – Protons, Electrons and Neutrons in ChlorineĬhlorine is a chemical element with atomic number 17 which means there are 17 protons in its nucleus. 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. How does the atomic mass determine the density of materials? Density of Chlorine The atomic mass number determines especially the atomic mass of atoms. The mass number is different for each different isotope of a chemical element. 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. For other isotopes, the isotopic mass usually differs 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). Therefore this resulting atomic mass is calculated from naturally-occurring isotopes and their abundance. Note that each element may contain more isotopes. How does the atomic number determine the chemical behavior of atoms? Atomic Mass of Chlorine Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. Chlorine is a chemical element with atomic number 17 which means there are 17 protons and 17 electrons in the atomic structure. ![]()
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