3. Elements are arranged side by side in order of
increasing atomic number – makes it possible
to see commonalities among them.
Vertical – Groups/Columns of the periodic
table
Horizontal – Periods/Rows of the periodic
table
4. The atomic radius is one-half of the distance
between the nuclei of two atoms of the same
element when the atoms are joined.
6. Atomic Radius Increases Down a group
◦ Greater energy levels and orbitals surrounding
nucleus
◦ Outer electrons are further away from nucleus
◦ Shielding effect occurs as we go down the group
◦ Shielding effect: The reduction of attractive force
between a nucleus and its outer electrons due to
blocking effect of inner electrons
7.
8. Atomic Radius Decreases across a period
Energy level stays the same
◦ No shielding changes happen
◦ Increase in # of protons, therefore positive charge
increases
◦ Pulls valence electrons closer
9. Atomic number
increases
Energy level (orbitals)
increases
Shielding occurs
Decrease nuclear
charge
Radius increases
Atomic number
increases
Same Energy level , no
shielding
Increase in nuclear
charge,
Pulls electrons in tight
and decrease radius
Down a group Across a period
10. An ion
◦ is an atom or group of atoms that
has a positive or negative charge
◦ Cations
An ion with a positive charge
Metals
◦ Anions
An ion with a negative charge
Nonmetals
11. ◦ The energy required to
remove an electron from an
atom is called ionization
energy.
12. ionization energy is high,
◦ takes a lot of energy to remove the outermost
electron
ionization energy is low,
◦ takes only a small amount of energy to remove the
outermost electron.
Smaller atomic radius, what do you think the
IE is? Why?
◦ High IE, small radius, high nuclear charge therefore
holding valence electrons tight
13. Ionization energies can help you predict what
ions an element will form.
◦ It is relatively easy to remove one electron from a
Group 1A metal atom, but it is difficult to remove
a second electron.
◦ This difference indicates that Group 1A metals
tend to form ions with a 1+ charge
15. The ability of an atom to attract and hold an
extra electron
- Measured as the energy change that occurs
when an electron is added to an atom
- When an atom gains an extra electron it
becomes negative
- Electron affinity can be either a positive or
negative numerical value
- Negative Value: atom releases energy when it
gains an electron
- Positive Value: atom must absorb energy for
the electron to be added
16. Becomes More negative as we move from left
to right across a period
Explained by nuclear charge, atomic radius
and shielding effects
As we move down the groups, electron
affinity becomes less negative
17. ◦ Electronegativity
the ability of an atom of an element to attract
electrons when the atom is in a compound.
18. The least electronegative element in
the table is cesium, with an
electronegativity of 0.7.
It has the least tendency to attract electrons.
When it reacts, it tends to lose electrons and form
cations.
19.
20. The most electronegative element is
fluorine, with a value of 4.0.
fluorine has such a strong tendency to attract
electrons
when it is bonded to any other element it either
attracts the shared electrons or forms an anion.
21. In general, 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.
Metals at the far left of the periodic table have low values.
By contrast, nonmetals at the far right (excluding noble
gases) have high values.
Values among transition metals are not as regular.
Notas del editor
Weather changes day to day
Weather is related to your location on the globe
Florida…sunny and warm
Minnesota….cool and rainy
Rain forest recieves more rain then a dessert
TRENDS IN THE WEATHER
Like the weather… elements on the periodic table and their characteristics are related to where they are located on the table
What is the seasonal trends of weather here?
How is knowing the trends in the weather for a specific area helpful?
Planting, building, etc…
We think of atoms in a spherical manner, this is not necessarily the case, but it allows us to look at electrons in a more simplistic way.
As the atomic number increases within a group, the charge on the nucleus increases and the number of occupied energy levels increases.
The increase in positive charge draws electrons closer to the nucleus.
The increase in the number of occupied orbitals shields electrons in the highest occupied energy level from the attraction of protons in the nucleus.
The shielding effect is greater than the effect of the increase in nuclear charge, so the atomic size increases.
- DEMONSTRATE SHIELDING WITH SEVERAL STUDENTS AND A NUCLEUS
In summation
Nonmetals tend to form anions. Metals tend to form cations
When an ion is removed from an atom the ion becomes more positively charged
Called a Cation
Nonmetals tend to form anions. Metals tend to form cations
Which one do you think is easier to happen? Negative or positive?
Why?
Negative because it can more easily take in an extra electron – is it easier to warm up or to cool off?
Left to right, nuclear charge increases, atomic radius ecreases, and shileding effect remains the same, so attractive force nucleus can exert on another electron increases