Uranium
The sign or abbreviation to represent an element is called an "atomic symbol", and there is a distinct one for each element. Every atomic symbol begins with a capital letter, which may constitute the entire symbol but is usually followed by a lower case letter.
CD is an invalid element symbol. Element symbols must only have one capitalized letter. This is also an invalid substance as there is no element with the symbol "D" However "C" is a valid symbol for Carbon and the atomic number is 6
Manganese is a metal element. Atomic number of it is 25.
Na There is no atomic element.
The symbol for the chemical element sodium is Na and its atomic number is 11.
Atomic Symbol
Atomic Symbol
The sign or abbreviation to represent an element is called an "atomic symbol", and there is a distinct one for each element. Every atomic symbol begins with a capital letter, which may constitute the entire symbol but is usually followed by a lower case letter.
The atomic number of the element with the symbol Be (Beryllium) is 4.
The element represented by the letter 'U' is uranium (atomic number 92).
CD is an invalid element symbol. Element symbols must only have one capitalized letter. This is also an invalid substance as there is no element with the symbol "D" However "C" is a valid symbol for Carbon and the atomic number is 6
Manganese is a metal element. Atomic number of it is 25.
Na There is no atomic element.
The symbol for the chemical element sodium is Na and its atomic number is 11.
The chemical symbol for the element sodium consists of a first capital letter and a second non capital letter: "Na". The atomic number of sodium is 11. (The term "first symbol" used in the question has no particular meaning of which I am aware.)
Krypton is an element with symbol Kr and atomic number 36.
It would be called an atomic/chemical symbol.