248 Cm has been produced only in milligram amounts. Curium is similar in some regards to gadolinium, its rare earth homolog, but it has a more complex crystal structure. Curium metal is lustrous, malleable, silver in color, chemically reactive, and is more electropositive than aluminum. Curium metal exist in two crystal forms, a double hexagonal close packed (dhcp) and a high temperature face-centered cubic close packed (fcc) structure. Metallic curium dissolves rapidly in dilute acid to form Cm(III) solutions. Curium metal surfaces rapidly oxidize in air to form a thin film possibly starting out as CmO, Oxidation then progressing to Cm 2 O 3, and eventually to form stable CmO 2. Note however that the formation of divalent compounds of curium such as CmO have never been observed in bulk form.
Video: Read-Only Memory (ROM): Definition & Types. Computers have various types of memory. Read-only memory (ROM) contains the instructions for what needs to happen when a computer is powered on. The data in ROM cannot be modified, or only with great difficulty, since these instructions do not need to be changed very often.
Main memory (sometimes known as internal memory or primary storage) is another name for RAM (and ROM). Main memory is usually used to store data temporarily. In the case of RAM, it is volatile (this means that when power is switched off all of the data in the memory disappears).