This post is about Chemistry Periodic Table Trends (Across a period).
Across a Period: Atomic size decreases, and electronegativity and ionization energy increase.
Trends:
Across a Period: Atomic size decreases, and electronegativity and ionization energy increase.
Down a Group: Atomic size increases, and electronegativity and ionization energy decrease.
Atomic Size Decreases Across a Period:
Reason: As you move from left to right across a period, the number of protons in the nucleus increases, while the number of electron shells remains the same.
The increased nuclear charge (positive charge from the protons) pulls the electrons closer to the nucleus, resulting in a smaller atomic radius (atomic size).
Tip: More protons and same number of electron shells, smaller atom.
Electronegativity Increases Across a Period:
Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond.
Reason: As the atomic size decreases, the nucleus becomes better able to attract electrons because the distance between the nucleus and the valence electrons is smaller.
The increased nuclear attraction makes the atom more likely to pull bonding electrons towards itself, thus increasing electronegativity.
Tip: Smaller atoms attract electrons better.
Ionization Energy Increases Across a Period:
Ionization energy is the energy required to remove one electron from a neutral atom in the gaseous state.
Reason: As the nuclear charge increases, electrons are held more tightly by the nucleus. This makes it more difficult to remove an electron, leading to a higher ionization energy.
Additionally, since the atomic radius is smaller, the outer electrons are closer to the nucleus, and removing them requires more energy.
Tip: Smaller atoms -> harder to lose electrons.
In summary:
The nucleus charge increases across a period (due to more protons).
The atomic radius decreases, pulling the outer electrons closer to the nucleus.
This results in higher electronegativity and higher ionization energy as atoms more strongly attract electrons and hold onto them more tightly.
Finished!
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