ATOMOS
Periodic Trends
Atomic Radii
1) As you move down a group, atomic radius increases
WHY? - The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase.
2) As you move across a period, atomic radius decreases.
WHY? - As you go across a period, electrons are added to the same energy level. At the same time, protons are being added to the nucleus. The concentration of more protons in the nucleus creates a "higher effective nuclear charge." In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius.
1) As you move down a group, atomic radius increases
WHY? - The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase.
2) As you move across a period, atomic radius decreases.
WHY? - As you go across a period, electrons are added to the same energy level. At the same time, protons are being added to the nucleus. The concentration of more protons in the nucleus creates a "higher effective nuclear charge." In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius.
First Ionization Energy
Definition: The energy required to remove the outermost (highest energy) electron from a neutral atom in its ground state.
1) As you move down a group, first ionization energy decreases.
WHY?Electrons are further from the nucleus and thus easier to remove the outermost one. "SHIELDING" - Inner electrons at lower energy levels essentially block the protons' force of attraction toward the nucleus. It therefore becomes easier to remove the outer electron
2) As you move across a period, first ionization energy increases.
WHY? - As you move across a period, the atomic radius decreases, that is, the atom is smaller. The outer electrons are closer to the nucleus and more strongly attracted to the center. Therefore, it becomes more difficult to remove the outermost electron.
Second and Higher Ionization Energies
Definition: Second Ionization Energy is the energy required to remove a second outermost electron from a ground state atom.
Subsequent ionization energies increase greatly once an ion has reached the state like that of a noble gas. In other words, it becomes extremely difficult to remove an electron from an atom once it loses enough electrons to lose an entire energy level so that its valence shell is filled.
Definition: The energy required to remove the outermost (highest energy) electron from a neutral atom in its ground state.
1) As you move down a group, first ionization energy decreases.
WHY?Electrons are further from the nucleus and thus easier to remove the outermost one. "SHIELDING" - Inner electrons at lower energy levels essentially block the protons' force of attraction toward the nucleus. It therefore becomes easier to remove the outer electron
2) As you move across a period, first ionization energy increases.
WHY? - As you move across a period, the atomic radius decreases, that is, the atom is smaller. The outer electrons are closer to the nucleus and more strongly attracted to the center. Therefore, it becomes more difficult to remove the outermost electron.
Second and Higher Ionization Energies
Definition: Second Ionization Energy is the energy required to remove a second outermost electron from a ground state atom.
Subsequent ionization energies increase greatly once an ion has reached the state like that of a noble gas. In other words, it becomes extremely difficult to remove an electron from an atom once it loses enough electrons to lose an entire energy level so that its valence shell is filled.
Electron Affinity
Definition: The energy given off when a neutral atom in the gas phase gains an extra electron to form a negatively charged ion.
1) As you move down a group, electron affinity decreases.
2) As you move across a period, electron affinity increases.
Definition: The energy given off when a neutral atom in the gas phase gains an extra electron to form a negatively charged ion.
1) As you move down a group, electron affinity decreases.
2) As you move across a period, electron affinity increases.
Electronegativity
Definition: Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons.
1) As you go down a group, electronegativity decreases
WHY? - because the added energy levels shield the power of the nucleus to attract electrons.
2) As you go across a period, electronegativity increases
WHY? - because the increase in nuclear charge makes the nucleus more powerful to hold on to electrons.
Definition: Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons.
1) As you go down a group, electronegativity decreases
WHY? - because the added energy levels shield the power of the nucleus to attract electrons.
2) As you go across a period, electronegativity increases
WHY? - because the increase in nuclear charge makes the nucleus more powerful to hold on to electrons.
Unknown Compound Lab Submission
Unknown Compound Part 2
Course Handouts
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Intermolecular Forces Explained
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