06-31-2022-Elements and Compounds part 1

Elements and Compounds

• Parts of Matter

  • Organisms are composed of matter

  • Matter: Anything that takes up space and has mass

• Definitions

  • Element: A substance that cannot be broken down into simpler substances by chemical reactions

  • Compound: A substance consisting of two or more elements in a fixed ratio

    • Characteristics different from its constituent elements (emergent properties)

Properties of Compounds

• Atomic Structure

  • A compound is made of atoms joined by bonds

  • Atoms and Bonds:

    • The number of protons determines an atom's identity

    • The distribution of electrons determines its bonding ability

• Example: Formic Acid

  • Composition: H, H, O

  • Property of compounds depends on its atomic composition and bonding

Essential Elements for Life

• Approximately 20-25% of the 92 natural elements are required for life (essential elements)

  • Main elements: Carbon, Hydrogen, Oxygen, Nitrogen (96% of living matter)

  • Remaining 4%: Calcium, Phosphorus, Potassium, Sulphur

  • Trace Elements: Required in minute quantities (e.g., Iron, Iodine, Copper)

Elements in the Human Body (Table 2.1)

• Major Elements:

  • Oxygen (O): 65.0%

  • Carbon (C): 18.5%

  • Hydrogen (H): 9.5%

  • Nitrogen (N): 3.3%

  • Calcium (Ca): 1.5%

  • Phosphorus (P): 1.0%

• Trace Elements: Include B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Si, Sn, V, Zn (less than 0.01% of mass)

Atomic Structure

• Atoms:

  • Composed of unique structures and smallest unit of matter retaining element properties

• Subatomic Particles:

  • Neutrons: No charge

  • Protons: Positive charge

  • Electrons: Negative charge forming a cloud around the nucleus

  • Mass of neutrons and protons is nearly equal and measured in daltons

Atomic Number and Mass

• Atomic Number: Number of protons in the nucleus

• Mass Number: Sum of protons and neutrons

• Formula: Mass number (A) = Atomic number (Z) + Neutron number (N)

Isotopes

• Isotopes are atoms of the same element with different numbers of neutrons

  • Radioactive Isotopes: Decay spontaneously, emitting particles and energy

Chemical Bonds and Molecules

• -Chemical Bonding:

  • Formed through sharing or transferring of electrons

• Covalent Bonds:

  • Sharing of a pair of valence electrons

  • A single bond shares one pair; a double bond shares two pairs

Bonding Capacity

• Valence Electrons: Electrons in the outermost shell determine an atom’s reactivity

• Atoms bond to complete valence shells, influencing compound formation

Practice Questions and Applications

• Understanding atomic structure and bonding is fundamental to identifying elements and their reactivity

• Use practice questions to solidify knowledge of atomic number, mass number, and differences between ionic and covalent bonds.