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Periodicity Notes.notebook
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January 13, 2020
Jan 86:02 PM
Ionization Energy
Ionization energy measures the attraction between the nucleus and outer electrons in an atom by stating the energy needed to remove an electron
Measures the energy required to remove an electron from a gaseous atom/ion to form a gaseous ion with a higher charge Energies are positive (endothermic, absorbs/requires energy) The higher the ionization energy, the harder it is to remove the electron
Na(g) Na+(g) + e
Na+(g) Na2+(g) + e
Jan 86:07 PM
Trends in Ionization Energy
From left to right across a period, ionization energy tends to increase (with a couple of exceptions). Increase in effective nuclear charge from left to right means electrons are more attracted to the nucleus and harder to remove this makes sense as nonmetals tend to want to GAIN electrons, not give them away.
Down a group, ionization energy tends to decrease. The valence electrons get further and further from the nucleus as atoms get bigger, and are less attracted...this makes them easier to remove
Periodicity Notes.notebook
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January 13, 2020
Jan 86:06 PM
First Ionization Energies for First 20 Elements
Jan 86:10 PM
If ionization energy increases from left to right, then explain why ionization energy for oxygen is lower than for nitrogen...
Periodicity Notes.notebook
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January 13, 2020
Jan 86:11 PM
Electron Affinity the energy change that occurs when one mole of electrons is added to one mole of gaseous atoms to produce one mole of gaseous ions:
X(g) + e X(g)
It is essentially the opposite of the first ionization energy, as we are ADDING electrons instead of removing them
Jan 86:17 PM
Electrons are attracted to the positive nucleus, so the first electron affinity is usually exothermic (gives off energy, reported as negative number)
Adding a second or third electron is generally endothermic (requires energy, positive number) since electrons are repelled by a negatively charged ion
Noble gases don't tend to form ions, so there is no electron affinity for them
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January 13, 2020
Jan 86:21 PM
Electron Affinities for First 18 Elements
Group 17 (halogens) have a large effective nuclear charge of +7 and an almost full valence shell strongly attract electrons Electron affinity is a large negative value VERY EXOTHERMIC, releases lots of energy
Jan 86:21 PM
Electron Affinities for First 18 Elements
Group 1 (alkali metals) have a small effective nuclear charge of +1 and would rather lose one electron than gain any, and attract electrons least..still a negative electron affinity, but only slightly exothermic, releases a bit of energy
Periodicity Notes.notebook
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January 13, 2020
Jan 86:22 PM
Electronegativity measures the ability of an atom to attract electrons in a covalent bond (a bond between two atoms in which electrons are SHARED instead of fully transferred)
Elements with high electronegativity have strong pulling power
Elements with low electronegativity have poor pulling power
Related to ionization energy, as it is also measuring how strongly valence electrons (or bonding electrons, as valence electrons are used to form covalent bonds) are attracted to the nucleus
Jan 86:29 PM
Electronegativity:
Increases from left to right across a period, as the effective nuclear charge increases and does a better job attracting electrons
Decreases down a group as the outer (bonding/valence) electrons are furthest from nucleus and not as strongly attracted
Periodicity Notes.notebook
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January 13, 2020
Jan 86:32 PM
Okay wait...ionization energy, electron affinity and electronegativity all seem pretty similar??? What is the difference?
Electron affinity and ionization energy are both properties of gaseous atoms and can be measured directly
Electronegativity is a property of AN ATOM IN A MOLECULE and can only be measured indirectly using experimental bond energies
Jan 86:34 PM
Why do metals conduct electricity and non metals do not?
Since metals generally have lower electronegativities and ionization energies than nonmetals, their electrons are able to move away from the nucleus more easily
Electricity is basically just the ability of electrons to move from one place to another metals are more willing to release electrons!
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January 13, 2020
Jan 131:04 PM
Pearson IB Text pg 105 110 Worksheet
q 9, 10, 11, 12, 15, 16, 18, 19
Feb 1410:29 PM
More on Ionization Energy
Recall first ionization energy is energy needed to remove one mole of electrons from the GROUND state of one mole of gaseous atoms. For hydrogen, this would mean removing an electron from the 1s orbital
H(g) H+(g) + e
Once an electron is removed from an atom, it is we consider it to be an infinite distance from the nucleus and part of n = ∞
Periodicity Notes.notebook
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January 13, 2020
Feb 1410:39 PM
This shows electrons returning from
excited energy states to lower energy.
Notice at high energy, the energy levels
become very close together they
CONVERGE.
Ionization energy corresponds to the
transition of an electron from n = 1 to
n = ∞ if we know the frequency or wavelength where the lines converge, we can calculate the energy of this transition TRANSITION ENERGY!
Feb 1410:43 PM
To calculate ionization energy for the n = 1 to n = ∞ transition, we must first recall:
Example: Determine the energy, in J, of a photon of red light, correct to four significant digits, given the wavelength for red light is 650.0 nm.
Periodicity Notes.notebook
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January 13, 2020
Feb 1410:50 PM
Example 2: Calculate the first ionization energy, in kJ/mol, for the hydrogen atom given that its shortest wavelength line in the Lyman series is 91.16 nm.
Feb 158:58 AM
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January 13, 2020
Feb 1410:56 PM