Download Valence Electrons

1.3 : Atoms vs. Ions,
Valence Electrons
1/11/16
SPS1. Students will investigate our current understanding of the atom. a. Examine the structure of the
atom in terms of proton, electron, and neutron locations, atomic mass and atomic number, atoms with
different numbers of neutrons (isotopes), and explain the relationship of the proton number to the
element’s identity. SPS4. Students will investigate the arrangement of the Periodic Table.
a. Determine the trends of the following: number of valence electrons, types of ions formed by
representative elements, location of metals, nonmetals, and metalloids, and phases at room temperature.
b. Use the Periodic Table to predict the above properties for representative elements.
Part I: Atoms vs. Ions
• atom = an electrically neutral unit of matter containing protons
and electrons in equal numbers.
• ion = an atom that has become charged, by the loss or addition of
electrons (never protons!).
•cation = a positive ion, created when an atom loses electrons.
•anion = a negative ion, created when an atom gains electrons.
• important to note: when an ion is created, it is because the
electron number changes. If the proton number were to change,
the element itself would change! Take a look:
• important to note: when an ion is created, it is because the
electron number changes. If the proton number were to change,
the element itself would change! Take a look:
sodium atom
11 protons
11 electrons
0 charge
sodium ion
11 protons
10 electrons
+1 charge
• important to note: when an ion is created, it is because the
electron number changes. If the proton number were to change,
the element itself would change! Take a look:
chlorine atom
17 protons
17 electrons
0 charge
chlorine ion
17 protons
18 electrons
-1 charge
The number of (protons,
neutrons, electrons)
changes when an atom
becomes an ion.
When forming an ion,
sodium (loses, gains) an
electron, forming a
(cation, anion).
Part II: Valence Electrons
• the number of electrons an atom has to lose or wants to gain
depends on the number of electrons it has on its outermost
energy level.
• valence electrons = an electron that is available to be lost or
gained in the formation of chemical compounds.
•the periodic table is arranged in such a way as to show the
repeating pattern in the number of valence electrons an atom
has (see below).
•the periodic table is arranged in such a way as to show the
repeating pattern in the number of valence electrons an atom
has (see below).
1
2
3
4
5
6
7
•only the e- on the outermost energy level are counted as
valence e-!
8
How many valence
electrons does
5
nitrogen have? ____
8
Argon? ____
3
Aluminum? ____
1
2
3
4
5
6
7
8
•only the e- on the outermost energy level are counted as
valence e-!
•all elements want 8 valence electrons for maximum stability.
•elements in the last column of the periodic table, known as
the noble gases, already have 8 valence electrons, so they
are very stable.
•due to this, noble gases do not form compounds with other
elements.
•due to this, noble gases do not form compounds with other
elements.
•the reason atoms with 1 -7 valence electrons form ions is to
look like a noble gas on the outside (but their proton number
does not change!).
•elements with 5, 6, or 7 valence electrons gain electrons to
make 8:
•7 + 1 = 8 (elements with 7 v.e.
have a -1 charge)
•6 + 2 = 8 (elements with 6 v.e.
have a -2 charge)
•5 + 3 = 8 (elements with 5 v.e.
have a -3 charge)
When forming an ion,
2
oxygen would gain ___
electrons since it has
6 v.e. to start with.
___
•due to this, noble gases do not form compounds with other
elements.
•the reason atoms with 1 -7 valence electrons form ions is to
look like a noble gas on the outside (but their proton number
does not change!).
•elements with 5, 6, or 7 valence electrons gain electrons to
make 8:
•7 + 1 = 8 (elements with 7 v.e.
have a -1 charge)
•6 + 2 = 8 (elements with 6 v.e.
have a -2 charge)
•5 + 3 = 8 (elements with 5 v.e.
have a -3 charge)
•elements with 1, 2, or 3 valence electrons lose electrons to
leave 8 exposed in the next level below:
•1 - 1 = 8 (elements with 1 v.e.
have a +1 charge)
•2 - 2 = 8 (elements with 2 v.e.
have a +2 charge)
•3 - 3 = 8 (elements with 3 v.e.
have a +3 charge)
•elements with 4 valence
electrons can either lose or
gain 4 electrons (they have
a 4 charge).
When forming an ion,
3
aluminum would lose___
electrons since it has
3 v.e. to start with.
___
•elements with 1, 2, or 3 valence electrons lose electrons to
leave 8 exposed in the next level below:
•1 - 1 = 8 (elements with 1 v.e.
have a +1 charge)
•2 - 2 = 8 (elements with 2 v.e.
have a +2 charge)
•3 - 3 = 8 (elements with 3 v.e.
have a +3 charge)
•elements with 4 valence
electrons can either lose or
gain 4 electrons (they have
a 4 charge).
•elements with 4 valence electrons can either lose or gain 4
electrons (they have a 4 charge).
•elements in the first 2 and last 6 columns of the periodic table
always have a valence electron number equal to their column
number.
•elements not found in the first two or last 6 columns of the
table have varying numbers of valence electrons, so their
charges vary as well.
•elements not found in the first two or last 6 columns of the
table have varying numbers of valence electrons, so their
charges vary as well.