71
During Class Invention
Shielding
Name(s) with Lab section in Group
______________________
__________________________________________________
1. How many electrons, protons and neutrons in the following atoms?
Atom
Nuclear Charge
#protons
#neutrons
# electrons
H
+1
1
0
1
He
+2
2
2
2
Ne
+10
10
10
10
2. How would we remove an electron from a hydrogen atom? How would we excite an
electron in a hydrogen atom?
By adding enough energy to ionize the atom (remove an electron). To excite an
electron in an atom we need to add an amount of energy that is exactly equal to the
energy separation between two energy level. (See the Bohr Model DCI to calculate
the energy required to excite an electron from n = 1 to n = 4 level.)
3. Write a chemical equation that describes the first ionization energy for
a) a hydrogen atom
energy + H(g) → H+(g) + 1e–
d) a helium atom
energy + He(g) → He+(g) + 1e–
e) a neon atom
energy + Ne(g) → Ne+(g) + 1e–
4. For each of the following atoms what ‘core’ charge are the electrons in the outer shell
attracted by?
a) Hydrogen Z = +1 there are no inner core electrons so the core charge is +1.
b) Lithium Z = +3. The electron configuration for lithium is 1s22s1. There are two inner
core electrons shielding the valence electron from some of the nuclear charge so the
core charge for the valence electron in lithium is +1.
c) Beryllium Z = +4. The electron configuration for beryllium is 1s22s2. There are two
inner core electrons shielding the valence electron from some of the nuclear charge
so the core charge for the valence electron in beryllium is +2.
d) Fluorine Z = +9. The electron configuration for fluorine is 1s22s22p5. There are two
inner core electrons shielding the valence electron from some of the nuclear charge
so the core charge for the valence electron in fluorine is +9.
