Term of the Day
An elementA substance containing only one kind of atom and that therefore cannot be broken down into component substances by chemical means. in the periodic tableA chart showing the symbols of the elements arranged in order by atomic number and having chemically related elements appearing in columns. from lanthanum (atomic numberThe number of protons in the nucleus of an atom; used to define the position of an element in the periodic table; represented by the letter Z. 57) to lutetium (atomic number 71); also called lanthanoidAn element in the periodic table from lanthanum (atomic number 57) to lutetium (atomic number 71); also called lanthanide. Sometimes lanthanum itself is not included in this series; sometimes lutetium is not.. Sometimes lanthanum itself is not included in this series; sometimes lutetium is not.