When an electron beam strikes a block of copper, x-rays of frequency 6 x 10^18 Hz are emitted. What is the wavelength of these x-rays? Answer in units of pm.

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

The big bang nucleosynthesis theory states that elements were produced in the first few minutes of the big bang while elements have their origins in the interiors of stars, forming much later in the history of the universe.

Compare and contrast physical changes with chemical changes.