Chapter 2L Atoms Isotopes Ions. Molcules

What is Matter?

anything that has mass and takes up space1. It exists in different states: solid, liquid, gas, and plasm

What Are Elements?

Elements are pure substances made of only one type of atom3.

Common Elements in Life The four major elements in living organisms are:

1⃣ Carbon (C) – Backbone of organic molecules. 2⃣ Hydrogen (H) – Found in water and biomolecules. 3⃣ Oxygen (O) – Essential for respiration. 4⃣ Nitrogen (N) – Key component of proteins and DNA4.

Trace Elements & Their Importance Trace elements are needed in small amounts but are essential for biological function

xamples:

• Iron (Fe) – Oxygen transport in blood.

• Zinc (Zn) – Enzyme function.

• Iodine (I) – Thyroid hormone production

Effects of Element Imbalances

• Iron Deficiency → Anemia, fatigue.

• Iron Excess → Organ damage.

• Iodine Deficiency → Goiter, thyroid issues.

• Iodine Excess → Thyroid dysfunctio

Atoms, Molecules, & Compounds

• Atom → Smallest unit of an element.

• Molecule → Two or more atoms bonded together.

• Compound → A molecule with different elements7

Atomic Structure

• Protons → Positive charge, found in nucleus.

• Neutrons → Neutral charge, found in nucleus.

• Electrons → Negative charge, orbit nucleus

Atomic Number & Mass Number

• Atomic Number → Number of protons in an atom.

• Mass Number → Protons + Neutrons9.

✅ Isotopes & Radioactive Isotopes

• Isotopes → Same element, different neutron count8.

• Radioactive Isotopes → Unstable, decay over time9.

Half-Life Calculation

Half-life = Time for half of a radioactive isotope to decay

Valency in Biology Valency

Number of electrons an atom can share or donate9.

Covalent Bonds

haring electrons (strongest).

Ionic Bonds

→ Electron transfer (medium strength).

Hydrogen Bonds →

Weak attractions (important in DNA & water

Electronegativity Factors

1⃣ Atomic size – Smaller atoms attract electrons more. 2⃣ Nuclear charge – More protons = stronger pull. 3⃣ Electron shielding – More inner electrons reduce attraction

Cations → Positive ions

(lost electrons).

Anions → Negative ions

(gained electrons)

Why Is Carbon Important?

• Forms stable bonds with many elements.

• Can create complex molecules (proteins, DNA)1

Three Types of Isomers

1⃣ Structural → Different arrangement of atoms. 2⃣ Geometric → Same formula, different spatial orientation. 3⃣ Enantiomers → Mirror-image molecules (important in drugs)14.

unctional Groups & Their Importance

Hydroxyl (-OH)	Carbohydrates	Increases solubility
Carbonyl (-C=O)	Lipids	Found in ketones & aldehydes
Carboxyl (-COOH)	Proteins	Acidic properties
Amino (-NH₂)	Proteins	Forms amino acids
Sulfhydryl (-SH)	Proteins	Stabilizes protein structure
Methyl (-CH₃)	DNA	Regulates gene expression
Phosphate (-PO₄³⁻)	Nucleic acids	Energy transfer (ATP)