Chemistry PDF - Atomic Theory, Bonds, and Polarity

JOHN DALTON - (1808) he created the first atomic theory Dipole - “Two Poles” - He was an English school teacher who performed Higher EN - Partial Negative many experiments on atoms. Lower EN - Partially Positive - Dalton viewed...

JOHN DALTON - (1808) he created the first atomic theory Dipole - “Two Poles” - He was an English school teacher who performed Higher EN - Partial Negative many experiments on atoms. Lower EN - Partially Positive - Dalton viewed atoms as tiny, solid balls. ELECTRONEGATIVITY DIFFERENCE (△ EN) DALTON’S THEORY 4 STATEMENTS 1. Atoms are tiny, invisible particles TYPE OF BOND ELECTRONEGATIV ITY DIFFERENCE 2. Atoms of one element are all the same. (△ EN) 3. Atoms of different elements are different. IONIC ≥ 1.7 4. Compounds form by combining atoms POLAR COVALENT 0.5 to 1.6 POLARITY OF A MOLECULE (INTERMOLECULAR FORCES) NON POLAR ≥ 0.4 COVALENT Chemical Bonds - Formed when atoms lose, gain, or share Electrons. GEOMETRICAL ALL SHAPES Types of Bonds LINEAR - A molecular shape where atoms are arranged in a straight line with a bond angle of 180°. Ionic Bonds ( Metal + Non Metals ) - Metal loses Electrons while Non Metals accept Electrons. Covalent Bonds ( Non-Metals + Non-Metals) - Neither of them may lose and gain Electrons. - Electron Pairs are being shared by both Atoms. POLARITY OF BONDS AND ELECTRONEGATIVITY Polarity - is the distribution of electric charge among EXAMPLES: the atoms connected by a bond. Carbon dioxide (CO2) Two factors may determine polarity: Beryllium chloride (BeCl2) Nitric oxide (NO) Based on Polarity Beryllium fluoride (BeF2) Hydrogen cyanide (H−C≡N) Geometrical Shapes via Valence Shell Electron Xenon difluoride (XeF2) Pair Repulsion (VSEPR) BENT - A molecular shape where the central atom has Electronegativity (EN) - measures the relative lone pairs that push bonded atoms into a bent or "V" tendency of an atom to attract electrons to itself when shape, resulting in bond angles less than 120° or 109.5°, chemically combined with other atoms. depending on the electron geometry. A Polar Covalent Bond is formed when electrons are shaped unequally: Formed an electric dipole  TETDRAHEDRAL - A symmetrical three-dimensional shape where four atoms are evenly spaced around the central atom, with bond angles of approximately 109.5°. EXAMPLES: Sulphur Dichloride (SCl2) Methylene (CH2) Nitrogen dioxide (NO2) TRIGONAL - A flat, triangular molecular shape with three bonded atoms around the central atom and bond angles of 120°. EXAMPLES: Methane (CH4) Silane (SiH4) EXAMPLES: SQUARE PLANAR - A molecular shape with four atoms positioned in a flat square around the central atom, Pnictogen Hydrides (XH 3) typically influenced by lone pairs or electron repulsion Xenon Trioxide (XeO 3) on the central atom, with bond angles of 90°. Chlorate Ion (ClO− 3) PYRAMIDAL - A three-dimensional molecular shape where three bonded atoms form a triangular base and a lone pair on the central atom creates a pyramid-like structure. Bond angles are slightly less than tetrahedral due to lone pair repulsion. EXAMPLES: Xenon tetrafluoride (XeF4) EXAMPLES: PCI3 S03  - CS2 - OCF2 POLARITY OF MOLECULES AND THEIR PROPERTIES Polarity, Solubility, and Miscibility Molecular Polarity - In simple terms, polar means oppositely charged, - Polarity is a separation of electric charge and non-polar means equally charged. leading to a molecule or its chemical groups - Polar bonds do not share electrons equally while having an electric dipole moment, with a non-polar bonds share electron negatively charged end and a positively charged end. Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. - Solubility is defined as the ability of a solid substance to be dissolved in a given amount of solvent. - Miscibility is the ability of the two liquids to combine or mix in all proportions, creating a homogenous mixture. Example of Lewis Structure - The general rule to remember about the solubility and miscibility of molecular compounds can be summarized in a phrase, “like dissolves like” or “like mixes with like”. This means that polar substances will only be dissolved or mixed with polar substances while nonpolar substances will be soluble or miscible with another nonpolar substance. - Now I want you to try the exercises below in order to assess how much you have understood the solubility - HF (and miscibility) rule of substances in relation to their polarity. Which of the following substances below will most likely mix with each other? Let us define the physical properties of substance: a. water (H2O) and chloroform (CHCl) A. Boiling point: the temperature at which the vapor pressure and atmospheric pressure of a b. benzene (C6H6) and chloroform (CHCl3) liquid substance are equal. B. Melting point: the temperature at which solid c. water (H2O) and vinegar (CH3COOH) becomes liquid. At this point, the solid and d. acetone (C3H6O) and toluene (C6H5CH3) liquid phases exist in equilibrium. C. Surface tension: the energy needed to increase e. carbon tetrachloride (CCl4) and water(H2O) the surface area by a unit amount; D. Viscosity: the resistance of the liquid to flow. E. Vapor Pressure: pressure exerted by a B. Bond Strength and Physical Properties of Covalent substance in its gaseous state. Compound F. Volatility: measures the rate at which a substance vaporizes(changes from liquid to gas) - Intermolecular forces of attraction (IMFA) which exist - In the simplest sense, boiling point, melting point, between molecules. viscosity and surface tension increase as the strength of intermolecular forces increases. On the other hand, vapor 1. There are several types of IMFA and below they pressure and volatility decrease with increasing strength are arranged from STRONGEST to WEAKEST. of IMFA. London dispersion forces increase as the Ion-dipole→H-bonding→dipole-dipole→dipole molecular mass of a substance increases. Unlike in -induced dipole→London forces of attraction. H-bonding, as the molar mass increases, the boiling 2. The strength of IMFA greatly affects the point, melting point, viscosity, and surface tension physical properties of substances such as boiling decrease. point, melting point, vapor pressure, surface tension, etc. Table 1: shows the comparison of the various types of IMFA while table 2 shows the physical properties of polar and nonpolar molecules as affected by the type of IMFA present. Table 2. General Properties of polar and nonpolar molecule