Collisions between atoms are often elastic, but sometimes inelastic collisions occur, and the lost kinetic energy can become internal energy in the atoms, exciting electrons to higher energy orbitals or even ejecting then from the atom entirely, which is called ionization (and the required energy the ionization energy).2 (a) a cs 133 atom (mass 133 amu) has an ionization energy of 4.0 ev.3 express this energy in joules. (b) what is the minimum speed that a o16 atom can have if it is to ionize a cesium atom at rest upon impact?

a) E = 6.4 1019 J    b)  v = 0.69 10⁴4 m / s

Explication

a) convert E = 4.0 eV

    1 eV = 1.6 10⁻¹⁹ J

   E = 4.0 eV (1.6 10⁻¹⁹ J / 1 eV)

   E = 6.4 10⁻¹⁹ J

b) Suppose we have a frontal shock and all the kinetic energy of oxygen is transferred to Cs

    Ei = K = ½ m v²

    Ef = 6.4 10⁻¹⁹ J

    ½ m v² = 6.4 10⁻¹⁹

The oxygen mass of the periodic table is

     PA = 15,999 u

     1u = 1.660 10⁻²⁷ kg

     Pa = 15,999 1,660 10⁻²⁷ kg

     m= Pa = 26,558 10⁻²⁷ kg

Let's calculate the speed

    v2 = 2 / m 6.4 10⁻¹⁹

    v2 = 2 / 26,558 10⁻²⁷ 6.4 10⁻¹⁹ =

    v = √0.4819 10⁸

    v = 0.69 10⁴4 m / s