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Chemistry periodicity Atomic and Ionic Radius

DO NOW : Take out HW to check. PERIODIC TABLES REQUIRED CALCULATORS NOT REQUIRED. Chemistry periodicity Atomic and Ionic Radius. The Size of an Atom. The size of an atom is a hard thing to grasp… how small is very small? 10 -10 m = 1 Angstrom (Å) … one tenth of a billionth of a meter.

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Chemistry periodicity Atomic and Ionic Radius

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  1. DO NOW: Take out HW to check. PERIODIC TABLES REQUIRED CALCULATORS NOT REQUIRED ChemistryperiodicityAtomic and Ionic Radius

  2. The Size of an Atom • The size of an atom is a hard thing to grasp… how small is very small? • 10-10 m = 1 Angstrom (Å) … one tenth of a billionth of a meter. • Angstroms are used to measure the radius of atoms.

  3. Periodic Trends - Atomic Radius • As you move down a column in the periodic table, the energy levels increase. • This is like adding layers to the onion, or wrapping tinfoil sheets on each other, getting bigger with each wrap. • Atoms will get larger as you move down a column. • Li < Na < K < Rb < Cs

  4. Periodic Trends - Atomic Radius • As you move across a row, the number of protons and electrons increase in the same layer, or energy level. • Add more positive charges (protons) and more negative (electrons), and the electrical pull increases, making the atom smaller. • Atoms will get smaller as you move across a row from left to right. • B > C > N > O > F

  5. Effective Nuclear Charge • Effective nuclear charge (Zeff) is the charge that an electron “feels” from the nucleus. • It is found by taking the atomic number (Z), and subtracting the number of inner electrons (S). • These inner electrons “shield” the outer electrons from the nucleus. • Zeff = Z – S • The higher thevalue of Zeff,the more thenucleus pullson the valenceelectrons.

  6. Ionic Radius • Cations have less electrons than protons, giving the nucleus greater pull on the electrons. • Cation radii are smaller than atomic radii. • K+ < K • Anions have more electrons than protons, lessening the pull on the nucleus and increasing the -/- repulsion of electrons, expanding the radius. • Anion radii are larger than atomic radii. • F- > F • Impact of ions is greater than columns on radius.

  7. Ionic Radius

  8. Recap • Moving down a column increases the radius. • Moving across a row decreases the radius. • Cationsdecrease the radius. • Anions increase the radius. • Greatest change in radius = cation/anion • Medium change in radius = up/down columns • Lowest change in radius = across row

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