Fundamentals of Chemistry: Atoms and Elements

Fundamentals of Chemistry: Part 1 - Atoms and Elements

• Learning Goals:
  • Understanding basic atomic structure
  • Understanding electron organization in simple elements
  • Representing electron configuration
  • Relating electron organization to Periodic Table position

The Human Body - Elemental Composition by Mass

• Elements: Hydrogen, Carbon, Nitrogen, Oxygen, Fluorine, Sodium, Magnesium, Phosphorus, Sulfur, Chlorine, Potassium, Calcium, Iron, Cobalt, Copper, Zinc, Selenium, Iodine.
• Percentage by Mass: (Values are approximate; specific percentages vary by individual and context)
  • Hydrogen (10%)
  • Carbon (18%)
  • Nitrogen (3%)
  • Oxygen (65%)
  • Fluorine (<0.01%)
  • Sodium (0.1%)
  • Magnesium (0.05%)
  • Phosphorus (1.2%)
  • Sulfur (0.2%)
  • Chlorine (0.2%)
  • Potassium (0.2%)
  • Calcium (1.5%)
  • Iron (<0.05%)
  • Others (in very small proportions)

Structure of the Atom

• Definition: Smallest unit of an element.
• Structure: Central nucleus surrounded by one or more electrons.
• Nucleus: Contains protons and neutrons.
• Electrons: Orbit the nucleus in specific regions (orbitals).
• Protons: Positively charged particles.
• Neutrons: Neutral particles.
• Hydrogen Atom Image: An image of a hydrogen atom with orbiting electrons, produced using a quantum microscope.

The Atomic Nucleus

• Composition: Protons and usually neutrons
• Mass: Protons and neutrons have approximately the same mass (one atomic mass unit).
• Charge: Proton is positive; neutron is neutral.
• Force: Held together by the nuclear force

Components of the Atom

• Particle: Proton, Neutron, Electron
• Mass: Proton(1), Neutron(1), Electron (very small: 5.5 x 10^-4amu or about 1/1800 of a proton or neutron).
• Charge: Proton(+1.6 x 10^-19 C), neutron(0), Electron(-1.6 x 10^-19 C)

Elements and Isotopes

• Elements: Atoms with different numbers of protons and thus, electrons.
• Isotopes: Atoms of the same element with the same number of protons (and thus electrons), but a different number of neutrons.
• Carbon Isotope Example: Carbon-12, Carbon-13, Carbon-14 are isotopes of carbon with varying numbers of neutrons and have slightly differing percentages for each isotope.

The Periodic Table

• Organization: Elements are organized by increasing atomic number.
• Groups (Columns): Elements in the same group have similar chemical properties.
• Periods (Rows): Elements in the same period have similar electron configurations.
• Formulator: Dmitri Mendeleev (1869)

Elements and Periodic Table

• Atomic Mass: Sum of protons and neutrons.
• Atomic Number: Number of protons or electrons in an atom
• Relationship to Periodic Table: Atomic Number determines where an element is located in the Periodic Table.
• Atomic Mass is greater than Atomic Number: Atomic mass includes protons and neutrons and the mass of electrons is comparatively negligible.

Atomic Mass and Molecular Masses

• Molecules: Composed of atoms;
• Molecular Mass: Sum of the atomic masses of atoms in the molecule.
• Carbon Dioxide Example: A CO2 molecule contains one Carbon atom and two Oxygen atoms; it's molecular mass can be calculated through summing the individual atomic masses.

Molecular Mass, Moles and Avogadro's Number

• Avogadro's Number: 6.02 x 10²³
• Mole: A unit used to represent a certain number of particles.
• One Mole: Contains 6.02 x 10²³ particles of that substance.
• NaCl (Table salt) Example: 1 mole of NaCl = 58.44 g (RMM = 58.44)

Moles and Molarity

• Moles: A unit of substance amount - no capital letter is used.
• Molar: A unit of concentration
• Molarity: Moles per liter (mol/L) or written as (M); capital M is used.

Electron Configuration: arrangement of electrons in the shell

• Helium Example: Helium (He), Atomic Number=2, 2 protons, 2 electrons, electron configuration 1s².
• Neon Example: Neon (Ne), Atomic Number=10, 10 protons, 10 electrons, electron configuration 1s²2s²2p⁶
• Fluorine Example: Fluorine (F), Atomic Number = 9, 9 protons, 9 electrons, Electron configuration 1s²2s²2p⁵.

Core and Valence Electrons

• Core Electrons: Filled electron shells that are closest to the nucleus.
• Valence Electrons: Outermost shell electrons. Participate in chemical reactions.
• Lewis's Dot Structure: Visual representation of valence electrons.

Electron Organisation

• Orbitals: Regions of space surrounding the nucleus where electrons reside. Each orbital can have a maximum of 2 electrons.
• Shells: Groups of equivalent orbitals are shells. Shells are further organized into subshells. Numbers increase from the nucleus outward.

Electronegativity and Polarity

• Electronegativity: Ability of an atom to attract electrons in a chemical bond.
• Polar Covalent Bond: Unequal sharing of electrons.
• Non-polar Covalent Bond: Equal or near-equal sharing of electrons.
• Ionic Bond: Complete transfer of electron(s).

Pauling Scale electronegativity

• Period Trend: Electronegativity generally increases across a period in the periodic table.
• Group Trend: Electronegativity generally decreases down a group in the periodic table.
• Bigger radius = lower electronegativity: Valence electrons are further away from the nucleus as the atomic radius increases.

Summary

• Periodic Table Location: Predicts element properties' and reactivity.
• Atomic Mass & Molecules: Necessary for calculations.
• Electron Organization: Determines chemical properties.
• Electronegativity: Determines type of bonding (polarity).
• Moles & Avogadro's Number: Essential calculations related to molar masses.

MCQ Quizzes

• Topic: Fundamentals of Chemistry, part 1 (Atoms)
• Purpose: Assist ongoing studies in Biochemistry.
• Use in Seminars: Used for discussions with further analysis.