As children move towards middle and late childhood, the relationship between physical activity and motor skill competence evolves and strengthens (Stodden et al. 2008). During middle childhood, a childâs perceived motor competence more closely estimates their actual motor skill competence.
In 1842 Gustav Mosander separated yttria, found in the mineral gadolinite, into three fractions which he called yttria, erbia, and terbia. The names erbia and terbia became confused in this early period. After 1860, Mosander's terbia was known as erbia, and after 1877, the earlier known erbia became terbia. The erbia of this period was later shown to consist of five oxides, now known as erbia, scandia, holmia, thulia and ytterbia.
Tungsten (atomic number 74, symbol W) is a metal and chemical element that was discovered in 1781 by the Swedish mineralogist and chemist Torbern Bergman. It was in 1783 when the element was isolated for the first time. Fausto Elhuyar and Juan Jose Elhuyar isolated tungsten from wolframite. Properties and Radioisotopes.