H
Hydrogen
Nonmetal
Atomic Number:
1
Atomic Mass:
1.007u
Appearance:
Description:
Hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state.
Atomic Structure:
Number of Protons:
1
Number of Electrons:
1
Number of Neutrons:
0
He
Helium
Noble Gas
Atomic Number:
2
Atomic Mass:
4.002u
Appearance:
Description:
Helium is the second lightest element and is the second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter.
Atomic Structure:
Number of Protons:
2
Number of Electrons:
2
Number of Neutrons:
2
Li
Lithium
Alkali Metal
Atomic Number:
3
Atomic Mass:
6.941u
Appearance:
Description:
Under standard conditions, lithium is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil.
Atomic Structure:
Number of Protons:
3
Number of Electrons:
3
Number of Neutrons:
4
Actinoids
All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.
Alkali Metals
One of the best-known applications of the pure elements is the use of Rubidium and Caesium in atomic clocks, of which Caesium atomic clocks are the most accurate and precise. A common application of the compounds of Sodium is the sodium-vapour lamp. Table salt, or Sodium Chloride, has been used since antiquity. Sodium and Potassium are also essential elements, having major biological roles as electrolytes.
Alkaline Earth Metals
All the discovered alkaline earth metals occur in nature. Experiments have been conducted to attempt the synthesis of element 120, the next potential member of the group, but they have all met with failure.
Halogens
The name 'halogen' means 'salt-producing'. When halogens react with metals they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide.
Lanthanoids
The informal chemical symbol Ln is used in general discussions of lanthanide chemistry to refer to any lanthanide. All but one of the lanthanides are f-block elements, corresponding to the filling of the 4f electron shell; lutetium, a d-block element, is also generally considered to be a lanthanide due to its chemical similarities with the other fourteen. All lanthanide elements form trivalent cations, Ln3+, whose chemistry is largely determined by the ionic radius, which decreases steadily from lanthanum to lutetium.
Metalloids
Typical metalloids have a metallic appearance, but they are brittle and only fair conductors of electricity. Chemically, they behave mostly as nonmetals. They can form alloys with metals. Most of their other physical and chemical properties are intermediate in nature. Metalloids are usually too brittle to have any structural uses. They and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics.
