Metalloid what classification criteria are used. Emsley recognised four metalloids (germanium, arsenic, antimony, and tellurium); James et al. listed twelve (Emsley's plus boron, carbon, silicon, selenium, bismuth, polonium, moscovium, and livermorium). On average, seven elements are included in such lists; individual classification arrangements tend to share common ground and vary in the ill-defined margins. A single quantitative criterion such as electronegativity is commonly used, metalloids having electronegativity values from 1.8 or 1.9 to 2.2. Further examples include packing efficiency (the fraction of volume in a crystal structure occupied by atoms) and the Goldhammer-Herzfeld criterion ratio. The commonly recognised metalloids have packing
Period 4 element can also be found in semiconductors. Germanium (Ge) is an element in period 4, between gallium and arsenic. Germanium, like silicon above it, is an important semiconductor and is commonly used in diodes and transistors, often in combination with arsenic. Germanium is fairly rare on Earth, leading to its comparatively late discovery. Germanium, in compounds, can sometimes irritate the eyes, skin, or lungs. Arsenic (As) is an element in period 4, between germanium and selenium. Arsenic, as mentioned above, is often used in semiconductors in alloys with germanium. Arsenic, in pure form and some alloys, is incredibly poisonous to all