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Introduction to Chemistry: Matter, Bonding, and Forces, Lecture notes of Physical Chemistry

A comprehensive introduction to the fundamental concepts of chemistry, covering topics such as matter, mixtures, pure substances, elements, compounds, chemical bonds, and intermolecular forces. It explains the different types of matter, the properties of covalent and ionic compounds, and the various types of intermolecular forces that govern the behavior of molecules. Well-structured, using clear headings and subheadings to guide the reader through the material. It also includes numerous examples and illustrations to enhance understanding.

Typology: Lecture notes

2023/2024

Available from 01/01/2025

mistymarie
mistymarie 🇵🇭

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BEGINNINGS OF CHEMISTRY
CHEMISTRY
- is the study of matter and the
changes it undergoes
a. Microscopic
b. Macroscopic
MATTER
- is anything that occupies space and
has mass.
TWO TYPES OF MATTER (separation
based on physical methods)
1. Mixtures
- is a combination of two or more
substances in which the substances
retain their distinct identities.
a. Homogeneous mixture the
composition of the mixture is the
same throughout. (ex. soft drink,
solder)
b. Heterogeneous
mixture—composition is not uniform
throughout. (ex.
2. Pure Substances
substance
- is a form of matter that has a
definite composition and distinct
properties.
TWO TYPES OF PURE SUBSTANCES
(separation by chemical methods)
a. Compounds
- a substance composed of atoms of
two or more elements chemically
united in fixed proportions.
- Compounds can only be separated
into pure components (elements) by
chemical means.
b. Elements
- is a substance that cannot be
separated into simpler substances
by chemical means.
- 118 elements have been identified
- 82 elements occur naturally on
Earth
- gold, aluminum, lead, oxygen,
carbon, sulfur
Physical means
- can be used to separate a mixture
into its pure components.
- distillation, magnet
molecule
- is an aggregate of two or more
atoms in a definite arrangement held
together by chemical forces
a. diatomic molecule
- contains only two atoms
- H2, N2, O2, Br2, HCl, CO
b. polyatomic molecule
- molecule contains more than two
atoms
- O3, H2O, NH3, CH4
How many protons and electrons are in
27Al 3+ ? 13
13 protons, 10 (13 3) electrons
How many protons and electrons are in
78Se2-? 34
34 protons, 36 (34 + 2) electrons
pf3
pf4

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CHEMISTRY

  • is the study of matter and the changes it undergoes a. Microscopic b. Macroscopic MATTER
  • is anything that occupies space and has mass. **TWO TYPES OF MATTER (separation based on physical methods)
  1. Mixtures**
  • is a combination of two or more substances in which the substances retain their distinct identities. a. Homogeneous mixture – the composition of the mixture is the same throughout. (ex. soft drink, solder) b. Heterogeneous mixture —composition is not uniform throughout. (ex.
  1. Pure Substances substance
  • is a form of matter that has a definite composition and distinct properties. TWO TYPES OF PURE SUBSTANCES (separation by chemical methods) a. Compounds
  • a substance composed of atoms of two or more elements chemically united in fixed proportions.
  • Compounds can only be separated into pure components (elements) by chemical means. b. Elements
  • is a substance that cannot be separated into simpler substances by chemical means.
  • • 118 elements have been identified
  • • 82 elements occur naturally on Earth
  • gold, aluminum, lead, oxygen, carbon, sulfur Physical means
  • can be used to separate a mixture into its pure components.
  • distillation, magnet molecule
  • is an aggregate of two or more atoms in a definite arrangement held together by chemical forces a. diatomic molecule
  • contains only two atoms
  • H2, N2, O2, Br2, HCl, CO b. polyatomic molecule
  • molecule contains more than two atoms
  • O3, H2O, NH3, CH How many protons and electrons are in 27Al 3+? 13 13 protons, 10 (13 – 3) electrons How many protons and electrons are in 78Se2-? 34 34 protons, 36 (34 + 2) electrons

ionic compounds

  • consist of a combination of cations and an anions
  • The formula is usually the same as the empirical formula
  • The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero
  • The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds. TYPES OF CHEMICAL BONDS Chemical Bonds
  • net forces of attraction that hold atoms together 1. Covalent Bond
  • attraction between the nucleus of the 1st atom and the e-’s of the 2nd atom; and the attraction of the nucleus of the 2nd atom and the e-’s of the 1st atom
  • sharing of e-
  • atoms of non-metals combine
  • electronegativity difference is 0 to < 2 Electronegativity
  • is the ability of an atom to attract toward itself the electrons in a chemical bond. Electronegativity - relative, F is highest Properties of Covalent Compounds ◦ intermolecular forces of attraction is weak ◦ gas, liquid or low-mp solid ◦ insoluble in H2O (mostly) ◦ aqueous solutions do not conduct electricity Properties: Bond Energy ◦ amount of energy involved when bond is broken ◦ amount of energy released when bond is formed ◦ strong bond; ↑ bond energy Properties: Bond Length ◦ distance between the nuclei of atoms forming the bond ◦ strong bond; ↓ bond length Properties: Bond Order ◦ # of bonds between atoms ◦ single, double or triple ◦ strong bond; ↓ bond length; ↑ bond order 2. Ionic Bond
  • attraction between cations and anions
  • atoms of metal and nonmetal combine
  • atoms with a large difference in electronegativities (≥2)
  • metals lose e- (cations), nonmetals gain e- (anions) and the total net charge is 0 Valence electrons
  • are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding. Electron configuration
  • is how the electrons are distributed among the various atomic orbitals in an atom.

Intermolecular Forces of Attraction (IMFA)

  • Attractive forces between molecules
  • Versus intramolecular forces of attraction: covalent or ionic Intermolecular Forces of Attraction
  1. Dipole – dipole forces
  2. Ion- dipole forces
  3. London – dispersion forces (induced dipole forces)
  4. Ion - ion forces
  5. Hydrogen bonding Dipole-dipole forces
  • between polar (covalent) molecules
  • 0.4 < electronegativity difference <
  • The larger the dipole moment, the greater the force Ion-dipole forces
  • attraction between an ion (cation or anion) and a polar molecule
  • Depends on the charge and size of the ion and on the magnitude of the dipole moment and size of the molecule. What type of interaction takes place between the non-polar molecules? London dispersion forces
  • van der Waals interaction
  • attractive forces in all (covalent) molecules
  • usually increase with molar mass because molecules with larger molar mass tend to have more electrons,
  • increase in strength with the number of electrons. Dispersion forces, Ion- dipole forces and dipole- dipole forces are collectively known as Van der Waals forces of attraction. Ion-ion forces
  • Electrostatic forces
  • attractive forces between cations and anions in ionic compounds Hydrogen bond
  • special type of dipole-dipole interaction between the H atom in a polar bond and an electronegative O, N or F atom The stronger the IMF’s, the tighter the molecules cling to each other, the harder it is to separate them.