R-AECHE-15

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Patterns in the Periodic table:

Across the period, atomic radius will decrease. (increasing electrons will increase attraction between them and nucleus, decreasing radius)

Going down groups, atomic radius will increase. (shells are being added).

• Electrons are added to a new shell as you go down a period.
• Nuclear charge increases,
• Effective nuclear charge

Larger atoms mean that valence electrons can be lost more easily, as they are further away from the nucleus and thus experience less weak nuclear attraction force.

Valency:

• Valency is the combining power of an atom and is equal to the number of hydrogen atoms it could combine with or displace from a compound. (Hydrogen has a valency of 1)

• Valency and number of valence electrons are not the same thing

• e.g. Nitrogen:

  • Nitrogen has a valency of 3, thus to achieve stability via gaining the electron configuration of nearest noble gas, it must lose 3 electrons.
  • Here, the number of valence electrons is 5, but the valency is 3.

• Principle quantum shells - refers to the shells of an atom. e.g. Sodium's principle quantum shells represents 2,8,1.

• Nuclear attraction is derived from the nuclear charge of an element minus the number of inner electrons shielding the outer electrons.

• Electronegative - higher density of electrons

• Going across a period will increase nuclear charge!

• If the molecule is symmetrical it is non-polar and doesn't have dipole-dipole

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