Properties of Ionic and Covalent Compounds. Intermolecular Forces

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1 Properties of Ionic and Covalent Compounds Intermolecular Forces

2 Physical Properties & Bond Types Physical properties of substances are affected by the attractive forces between particles Greater attraction between the molecules more energy is required to overcome the attractive forces between molecules Increased melting point or boiling point Solubility depends on like dissolves like.

3 Structure of an Ionic Solid Ionic Compounds form a three-dimensional network called a crystal (or crystal lattice) Each ion is attracted to multiple ions of the opposite charge

4 Forces Between Particles Due to the attraction of oppositely charged ions There is a greater attraction between ions of greater charge Strongest forces between particles found in ionic compounds Interionic Forces

5 General Properties of Ionic Compounds High melting/boiling points Solids at room temperature Many are soluble in water Ions separate when dissolved in water Liquids & Solutions Good Conductors Ions are separated any substance that has separate charges allow for conduction of electricity Solids Poor conductors No separation of ions

6 General Properties of Covalent Compounds Lower Melting Points than ionic compounds Intermolecular Forces aren t as strong as interionic forces Cannot conduct electricity as solid, liquid, or when dissolved molecules will not separate into ions Will dissolve in liquids with similar molecular polarity Like dissolves like

7 Nonpolar Covalent Bonds Some atoms have similar attraction for electrons, so the shared pair(s) will be evenly distributed between each atom There are no positive or negative sides This is referred to as a nonpolar covalent bond Because there is no separation of charge within the molecule, they have little or no attraction for one another

8 General Properties of NonPolar Covalent Compounds Really low melting points and boiling points Many are gases at room temperature Cannot conduct electricity as solid, liquid, or when dissolved molecules will not separate into ions Will dissolve in liquids with similar molecular polarity Like dissolves like

9 Polar Covalent Bonds Some atoms have a greater attraction for electrons than other atoms Due to greater electronegativity When these atoms form a covalent bond, the electrons will not be shared equally This is referred to as a polar covalent bond

10 Attraction Between Polar Compounds Hydrogen is positive Hydrogen is positive The negative part of one water molecule is attracted to the positive part of another water molecule Oxygen is negative

11 Intermolecular Forces Polar molecules are attracted to each other via the negative end of one molecule being attracted to the positive end of another molecule Not as strong as ionic forces, but stronger than the very weak forces that (barely) exist between nonpolar molecules Dipole Forces

12 Differences Between Polar and Nonpolar Covalent Compounds Polar molecules will attract each other SLIGHTLY Nonpolar molecules have no attraction for each other Polar Compounds will have slightly higher melting points, but not as high as ionic compounds Still no ability to conduct charges Polar compounds will dissolve in other polar compounds, but not in nonpolar compounds

13 Boiling Point Comparison

14 Forces Between Particles Hydrogen Bonding Strongest of the intermolecular forces Attraction between molecules, not ions Hydrogen bonding arises where hydrogen atoms are bonded to highly electronegative elements such as F, O, and N

15 Forces Between Particles Hydrogen Bonding

16 General Properties of Covalent Compounds that Exhibit Hydrogen Bonding Lower Melting Points than ionic compounds, but higher than nonpolar or polar covalent compounds Intermolecular Forces aren t as strong as interionic forces, but Hydrogen bonding is stronger than other intermolecular forces Cannot conduct electricity as solid, liquid, or when dissolved Still no ions Will dissolve in liquids with similar molecular polarity Like dissolves like