4.5 Periodic Trends Flashcards
Atomic size, ionization energy, and electronegativity
How do we define the atomic size of an atom
Using atomic radius - distance between the center of an atom to outermost shell
How do we define the atomic size of a diatomic atom
One half the distance between the centers of a homonuclear diatomic molecule
What are the 3 factors that influences the atomic size of an atom?
- Number of protons in the nucleus (nuclear charge)
- Number of electron shells
- Number of electrons held between the nucleus and valence electrons (shielding effect)
How does the atomic radius increases on the periodic table?
Increases from right to left and up to down of the periodic table
What does energy levels have to do with how big/small the atomic radius gets?
Each period in the periodic table represents another electron shell, and each energy level is larger than the last one
What is the shielding effect of the atomic radius
Describes the balance between the pull of protons on valence shells and repulsion forces from inner electrons
What does the shielding effect do?
It explains why valence electrons are more easily removed from an atom
More shielding, more spread out valence shells are -> bigger atomic size
How does the nuclear charge determine the atomic radius?
Number of protons increases while number of electron shells stay the same -> Net pull of electrons towards the nucleus
What is an ion?
An atom that has lost/gained electrons
Define ionization energy
The energy required to remove the most loosely held electron from an atom
Are metal ions smaller or bigger than their original atom?
Smaller; they loose electrons easily
Are non-metal ions smaller or bigger than their original atom?
Bigger; they gain electrons easily
Why is it harder to remove electrons from an atom with high ionization energy?
They have a stronger nuclear attraction between the nucleus and the valence electrons, hence it requires more energy
Why is it easier to remove electrons from atoms further down a group?
Atoms get larger, meaning electrons are further away from the nucleus - weaker shielding effect
Why is it harder to remove electrons as you move left to right of the periodic table?
Decrease in atomic size and increase in effective nuclear charge
What is the definition of electronegativity?
Potential energy released when an electron is added to a gaseous atom/ion
Measure of tendency of an atom to attract a bonding pair of electrons
Why does electronegativity decrease as you go down a group?
Less energy is released when electrons are added because they can’t move as close to the nucleus
What is the relation between electronegativity and ionization energy?
Both related to atomic size
Large atoms have low ________ and ________, therefore they tend to _____ electrons
Ionization energy, electronegativity, lose
Small atoms have high _____________ and _________, therefore they tend to ______ electrons
Ionization energy, electronegativity, gain
What is the exception for the electronegativity rule?
Noble gases; the outer shell is filled and it’s hard to loose/gain electrons
What is the Pauling scale?
A scale based on the electronegativity of bonded atoms
