Valence Electrons
An atom consists of a positively charged nucleus and
some negatively charged electrons. These particles interact with
each other at all times by means of electrical forces, also known
as electrostatic or Coulombic forces.
Electrostatic forces can attract particles together
or drive them apart. Oppositely charged particles, like a nucleus
(+) and an electron (-), are attracted to one another. Similarly
charged particles, like a pair of electrons, repel each other.
Lewis postulated (and it was later confirmed) that
an atom's electrons could be divided into two groups: core and valence.
The core electrons stay very close to the nucleus and constantly
feel its strong attraction. These electrons are unaffected by neighboring
atoms.
Valence electrons, on the other hand, stay
farther away from the nucleus and experience much less electrostatic
attraction. As a result, these electrons are readily influenced
by neighboring atoms.
Review problems
Test your understanding of this material by filling
in the blanks in the following paragraph. Write your answers on
a piece of paper and then click "answers" to see the complete
paragraph. If you have trouble with this material, try writing the
same kind of paragraph about the carbon atom (atomic number 6, mass
12).
The oxygen atom. The oxygen atom has an atomic
number of 8 and an atomic mass of 16. From this information, you
know that the oxygen nucleus contains ____ protons, ____
neutrons, and ____ electrons. The oxygen nucleus carries an electrical
charge of ____. An oxygen atom also contains ____ electrons. Each
electron carries an electrical charge of ____. The nucleus and the
electrons ____ (attract/repel) each other, while pairs of electrons
____ (attract/repel) each other. The ____ can be divided into two
groups: ____ and ____. The ____ electrons, of which there are ____,
stay very close to the nucleus. The ____ electrons, of which there
are ____, are much farther away from the nucleus and participate
in chemical bonding.
answers
answers
for carbon
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