Lecture 6.3- Periodic Trends

Section 6.3 Lecture on Periodic Trends for Prep Chemistry(P).

1. Bellwork- Groups
Draw a simple periodic table and label the
following:
a)Alkali metals
b)Alkaline earth metals
c)Halogens
d)Noble gases
e)Transition metals

2. The atomic radius measures an
atom’s size.
It is one half of the distance between the
nuclei of two atoms of the same element
when the atoms are joined.

3. Group and Periodic Trends in Atomic Size
In general, atomic size increases
from top to bottom within a
group and decreases from left to
right across a period.

6. A neutral atom contains an equal
number of protons and electrons.
When an atom gains or loses
electrons it is no longer neutral.
It becomes a charged ion.
An ion has a charge.

7. If an atom or a compound becomes
charged it is called an ion

8. A positive ion is called a cation
A negative ion is called an anion
Positive
+
Positive
+
Positive
+

9. Anakin
NEGATIVE

10. When an atom gains an electron it
gains an additional negative charge.
A Chlorine atom will gain one electron to
become a Chlorine anion.
Cle
-
_

11. An Oxygen atom will gain two electrons
making an Oxygen ion with a charge of
negative two.
Oe
-e
-
_
2-

12. Atoms of elements from the left side of
the periodic table will lose electrons.
When an atom loses an electron it
has more protons than electrons,
so it is a positively charged ion.

13. Sodium will lose one electron
to create a sodium ion with a
“plus one” charge
Na
+

14. A Magnesium atom will lose two
electrons to form an ion with a
charge of positive two.
Mg
+
e
-
2+

15. The energy required to remove
an electron from an atom is
called ionization energy.
First ionization energy tends to
decrease from top to bottom within a
group and increase from left to right
across a period.

17. Electronegativity is the ability
of an atom of an element to
attract electrons when the atom
is in a compound.
Electronegativity values decrease
from top to bottom within a group.
For representative elements, the
values tend to increase from left to
right across a period.