Covalent Substances - A0S 1 - Chapter 2

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Intramolecular Bonds

Bonds within a molecule (eg. covalent, ionic, metallic bonds)

Lewis Structure

Dot & Cross notation to show which atoms the electrons belong to

Non-bonding electrons

Electrons not part of the bond

Diatomic molecule

Contains 2 atoms

Polyatomic molecule

Contains more than 2 electrons

Types of VSEPR shapes

Tetrahedral, Pyramidal, Linear, Bent, Trigonal Planar

Structural Formula

Each bond is donated by lines, unlike the Lewis Structure

Non-polar bonds

If the electronegativity is same, or under 0.4 amongst the atoms.

Electron Density

Probability of electron being present at a particular place in the atom.

Polar Bonds

Electron distributivity is unequal and one atom pulls away electrons (creating a dipole).

Polarity

The electronegativity of the element/atom

If difference in electronegativity is more than 1.7?

>1.7: Ionic bond

<1.7: Polar covalent bond

Asymmetrical Vs. Symmetrical Molecules

Asymmetrical molecules are polar and symmetrical molecules are non-polar.

Types of Intermolecular Forces (between molecules)

Hydrogen-Hydrogen Bonding

Dipole-Dipole Bonding

Dispersion Forces

Temporary Dipoles

Temporary movement of electrons that causes a partial charge.

Strength Of Dispersion Forces

Increases as molecule size increases (is said to be the weakest of the other forces)

Dipole-Dipole Attraction

Happens between polar molecules to create a permanent dipole.

The more polar a molecule is, the stronger the dipole-dipole bond.

Hydrogen-Hydrogen Bonding

When Hydrogen bonds with Nitrogen, Oxygen or Fluorine (strongest of the bonds)

Reason For Other Polar Atoms Not Being Able To Bond Through Hydrogen-Hydrogen Method.

Others are generally larger, and electron density is more spread out - creates weaker dipole-dipole bonds.

Allotropes

Elements that can have several structural arrangements. (Only amongst the same element)

Allotropes of Oxygen

Oxygen gas, ozone

Allotropes Of Carbon

Diamond, Graphite

Properties Of Diamond

Hard

Non-conductive

Every carbon bonds with 4 other carbons

Brittle

Properties Of Graphite

Conductive (due to delocalized electron)

Slippery

Soft

Greasy

Properties of Amorphous (Irregular Carbon Structures)

Conductive

Non-crystalline

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