Chemistry of Elements Quiz

Study Notes

Atom - Single unit of an element. Example: Helium (He)
Element - Substance made of only one type of atom. Example: Gold (Au)
Most Common Biological Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).
Rare Elements in Biology:
- Sodium (Na) and Potassium (K) found in electrolytes and nerve impulses
- Magnesium (Mg) and Calcium (Ca) found in chlorophyll and bone structures
Valence Electrons: Electrons in the outermost shell of an atom, involved in chemical bonding.
- Carbon (C) has 4 valence electrons, similar to Silicon (Si).
- Nitrogen (N) has 5 valence electrons, similar to Phosphorus (P).
- Oxygen (O) has 6 valence electrons, similar to Sulfur (S).
Biological Ions:
- Ions are atoms that have gained or lost electrons, forming a charge.
- Anions: Gain electrons, become negatively charged. Example: Chloride (Cl-)
- Cations: Lose electrons, become positively charged. Example: Sodium (Na+)
- Group 1 and 2 elements in the periodic table are most likely to form cations.
- Group 17 elements in the periodic table are most likely to form anions.
Elements in Biomolecules:
- Carbohydrates: C, H, O
- Lipids: C, H, O (with some P)
- Proteins: C, H, O, N, (with some S)
- Nucleic Acids: C, H, O, N, P

Types of Chemical Bonds:
- Covalent Bonds: Sharing of electrons between atoms. Example: Water (H2O)
- Ionic Bonds: Transfer of electrons between atoms, forming ions with opposite charges. Example: Table Salt (NaCl)
- Hydrogen Bonds: Weak attraction between a hydrogen atom covalently linked to an electronegative atom (like oxygen or nitrogen) and a neighboring electronegative atom. Example: Water molecules.
Covalent Bonds:
- Nonpolar Covalent Bond: Equal sharing of electrons between atoms. Example: Methane (CH4)
- Polar Covalent Bond: Unequal sharing of electrons due to different electronegativity. Example: Water (H2O)
Electronegativity: The tendency of an atom to attract shared electrons in a covalent bond
- Decreases from top to bottom and from right to left on the periodic table
Biological Ions:
- Na+, K+, Ca2+, Mg2+ are all cations (positively charged)
- Cl-, PO43-, HCO3- are all anions (negatively charged)
Electronegativity and Bonding Capacity:
- Bonding Capacity: Refers to the number of covalent bonds an atom can form. Determined by the number of valence electrons available for sharing.
- Electronegativity: Influences the type of bond formed. Higher electronegativity difference leads to more polar bonds.
- Bonding Capacity and Electronegativity together determine the shape and properties of molecules. This is important in biology as it determines interactions between molecules in cells and tissues.