Periodic TrendsPeriodic Trends

Can Studying Chemistry Be Trendy?Can Studying Chemistry Be Trendy? As you look at the periodic table and focus in on the As you look at the periodic table and focus in on the

elements and their characteristics, you can see there are elements and their characteristics, you can see there are noticeable patterns (trends) that go across a period noticeable patterns (trends) that go across a period (horizontal row) on the periodic table.(horizontal row) on the periodic table.

These quantitative (able to measured with numbers and These quantitative (able to measured with numbers and units) characteristics that follow distinct patterns across units) characteristics that follow distinct patterns across the periodic table are called the periodic table are called periodic trendsperiodic trends..

Remember…Mendeleev didn’t get all the fame and Remember…Mendeleev didn’t get all the fame and fortune for nothing – he was crazy smart!fortune for nothing – he was crazy smart!

The periodic trends that we will be studying are:The periodic trends that we will be studying are: Atomic RadiusAtomic Radius Ionization EnergyIonization Energy Electron AffinityElectron Affinity ElectronegativityElectronegativity

Atomic RadiusAtomic Radius The The atomic radiusatomic radius of an element is an estimate of the of an element is an estimate of the

size of an atom from its nucleus to its outer perimeter.size of an atom from its nucleus to its outer perimeter. The Trend of Atomic RadiusThe Trend of Atomic Radius……

Atomic radius gets smaller as you move left to Atomic radius gets smaller as you move left to right on the periodic table.right on the periodic table. As you go across a row, you add more protons to the As you go across a row, you add more protons to the

nucleus and more electrons to the orbits – this means nucleus and more electrons to the orbits – this means more attraction between the opposing charges and the more attraction between the opposing charges and the orbits are pulled in even closer to the nucleus.orbits are pulled in even closer to the nucleus.

Atomic radius gets larger as you go top to bottom Atomic radius gets larger as you go top to bottom on the periodic table.on the periodic table. Each time you go down a spot on one of the columns on Each time you go down a spot on one of the columns on

the periodic table, you are adding another orbit – this the periodic table, you are adding another orbit – this additional orbit increases the size of the atom.additional orbit increases the size of the atom.

Understanding atomic radius will actually help us Understanding atomic radius will actually help us understand some of the other periodic trends.understand some of the other periodic trends.

Atomic RadiusAtomic Radius

Ionization EnergyIonization Energy The trend of ionization energy deals with The trend of ionization energy deals with ionsions – atoms that have lost or – atoms that have lost or

gained electrons. (Anions are negative ions; cations are positive ions).gained electrons. (Anions are negative ions; cations are positive ions). Ionization energyIonization energy is the energy needed to remove an electron from a is the energy needed to remove an electron from a

gaseous atom.gaseous atom. The Trend of Ionization Energy…The Trend of Ionization Energy…

Ionization energy increases as you go left to right on the periodic Ionization energy increases as you go left to right on the periodic table.table. As you go let to right, the radius of the atom is smaller because of As you go let to right, the radius of the atom is smaller because of

the greater attraction between the protons and electrons. The the greater attraction between the protons and electrons. The electrons are being held more tightly and closely by the nucleus. electrons are being held more tightly and closely by the nucleus. You have to fight to get one free.You have to fight to get one free.

Ionization energy gets weaker as you move down a column on the Ionization energy gets weaker as you move down a column on the periodic table.periodic table. As you go down a column, you add another orbit so the negative As you go down a column, you add another orbit so the negative

electrons are further away from the positive protons and the electrons are further away from the positive protons and the attractive force between them is not as strong. It’s easier for attractive force between them is not as strong. It’s easier for anyone to come by an rip off an electron.anyone to come by an rip off an electron.

Multiple Ionization EnergiesMultiple Ionization Energies The term “multiple ionization energies” refers to The term “multiple ionization energies” refers to

the taking of more than one electron from a the taking of more than one electron from a gaseous atom.gaseous atom.

The trend here is that it gets a lot tougher to take The trend here is that it gets a lot tougher to take more and more electrons from an atom.more and more electrons from an atom.

The first electron taken will seem easy The first electron taken will seem easy compared to the second. The second electron compared to the second. The second electron will be tougher than the first, but, will come away will be tougher than the first, but, will come away easier than the third and so on…easier than the third and so on…

As an electron is taken away, the protons are As an electron is taken away, the protons are acting on fewer electrons and can pull them in acting on fewer electrons and can pull them in even tighter.even tighter.

Ionization EnergyIonization Energy

Electron AffinityElectron Affinity Electron affinityElectron affinity is the energy released when is the energy released when

an electron is added to a gaseous atom.an electron is added to a gaseous atom. There is no clear pattern for the periodic trend of There is no clear pattern for the periodic trend of

electron affinity although there tends to be a electron affinity although there tends to be a general increase in electron affinity as you go general increase in electron affinity as you go from the left to the right on the periodic table.from the left to the right on the periodic table.

Note that you must spend energy to rip an Note that you must spend energy to rip an electron off of an atom and energy is released, electron off of an atom and energy is released, or given off, when an electron in added to an or given off, when an electron in added to an atom.atom.

Electron AffinityElectron Affinity

ElectronegativityElectronegativity ElectronegativityElectronegativity is the relative strength of attraction an atom has is the relative strength of attraction an atom has

for electrons while it is in a chemical bond.for electrons while it is in a chemical bond. Remember that chemical bonds can involve the sharing of pairs of Remember that chemical bonds can involve the sharing of pairs of

electrons. The atoms are literally fighting to gain possession of electrons. The atoms are literally fighting to gain possession of those electrons – the amount those electrons – the amount ““electron-grabbing muscleelectron-grabbing muscle”” they they have is called electronegativity.have is called electronegativity.

The Trend of ElectronegativityThe Trend of Electronegativity…… Electronegativity increases as you go left to right across the Electronegativity increases as you go left to right across the

periodic table.periodic table. There are more protons in the atoms as you go across the periodic There are more protons in the atoms as you go across the periodic

table and this means there is more positive charge to attract the table and this means there is more positive charge to attract the negative electrons.negative electrons.

Electronegativity decreases as you go down a column on the Electronegativity decreases as you go down a column on the periodic table.periodic table. You are adding more orbits so the electrons are further away from You are adding more orbits so the electrons are further away from

the protons and there is less attractive force to grab the electrons.the protons and there is less attractive force to grab the electrons.

ElectronegativityElectronegativity

THE ENDTHE END