Thus, each proton and neutron has a mass of about 1 amu. So as you go down the group 7A and element in the halogen family would have the same volume, the atomic mass increases. The acidic character of oxides of group 13 elements decreases down the group and the basic character increases. This is because they have smaller sizes, and hence small volumes. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Lithium, rubidium and caesium are much less abundant. Carbon: Value given for graphite form. This isotope of carbon has 6 protons and 6 neutrons. 2 Helium: Density at 0° Celsius. The chemical symbol for Hydrogen is H.. With a standard atomic weight of circa 1.008, hydrogen is the lightest element on the periodic table. The elements of group 13 have higher densities than group 2 elements. The densities of the Group 1 elements increase down the group (except for a downward fluctuation at potassium). The higher it is the more dense the substance is. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. This page explores the trends in some atomic and physical properties of the Group 1 elements - lithium, sodium, potassium, rubidium and caesium. Francium is radioactive and only has short lived isotopes formed from the decay of other elements. Isotopes Isotope of an element is defined by the sum of the number of protons and neutrons in its nucleus. Generally, the densities of all of the elements increase as you go down the group. Trends in Density. This trend is shown in the figure below: The metals in this series are relatively light— lithium, sodium, and potassium are less dense than water (less than 1 g cm-3). This is approximately the sum of the number of protons and neutrons in the nucleus. Density, or volumic mass, is a measure of mass per unit of volume, - either kilograms per cubic meter or grams per cubic centimeter. Acid-Base Characteristics. When it comes to the density of the metal, group one elements display a very low level of density of up to 1 gcm-3 which means that they can easily float on … Isotope: Atoms of the same element with the same atomic number, but different number of neutrons. 2 Density of diamond form is 3500. Sodium and potassium are the most abundant Group 1 elements on the Earth, and can be found in rock salt deposits formed from salt water evaporation. Notes on the Density of particular elements: Hydrogen: Density given for H at 0° Celsius. Relative atomic mass The mass of an atom relative to that of carbon-12. Hydrogen is a chemical element with atomic number 1 which means there are 1 protons and 1 electrons in the atomic structure.The chemical symbol for Hydrogen is H. With a standard atomic weight of circa 1.008, hydrogen is the lightest element on the periodic table. The alkali metals are so called because reaction with water forms alkalies (i.e., strong bases capable of neutralizing acids). The reason may be that as you go down a group, the atomic structure increases. The density increases from B to Tl. 2 Fluorine: Density given for F at 0° Celsius. Density (g cm −3) Density is the mass of a substance that would fill 1 cm 3 at room temperature. You will find separate sections below covering the trends in atomic radius, first ionisation energy, electronegativity, melting and boiling points, and density. The melting points of these elements are quite low, which is 180° Celsius in the case of Lithium, while it is 39° Celsius in the case of Rubidium. Hydrogen is a chemical element with atomic number 1 which means there are 1 protons and 1 electrons in the atomic structure. Nitrogen: Density given for N at 0° Celsius. Density. 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