We know the atomic number of hydrogen is one, so there's one proton in the nucleus. So let's go ahead and draw an atom of hydrogen. In a neutral atom, the number of protons is equal to the number of electrons, because in a neutral atom there's no overall charge and the positive charges of the protons completely balance with the negative charges of the electrons. So it's right here, so there's one proton in the nucleus of a hydrogen atom. So for hydrogen, hydrogen's atomic number is one. So we're going to talk about hydrogen in this video. And you can find the atomic number on the periodic table. Lithium – Properties Summary Element Lithium Atomic Number 3 Symbol Li Element Category Alkali Metal Phase at STP Solid Atomic Mass 6.941 Density at STP 0.535 Electron Configuration 2s1 Possible Oxidation States +1 Electron Affinity 59.6 Electronegativity 0.98 1st Ionization Energy 5.3917 Year of Discovery 1817 Discoverer Arfvedson, Johan August Thermal properties Melting Point 180.5 Boiling Point 1342 Thermal Conductivity 85 Specific Heat 3.6 Heat of Fusion 3 Heat of Vaporization 145.So the atomic number is symbolized by Z and it refers to the number of protons in a nucleus. The Standard English unit is pounds mass per cubic foot ( lbm/ft 3). 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 Lithium 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 Lithium Since the number of electrons is responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. Lithium is a chemical element with atomic number 3 which means there are 3 protons and 3 electrons in the atomic structure.

Li atomic number