unit 3

Atomic Structure

• Atom

  • Definition: The smallest part of an element that retains its identity.

• Subatomic Particles

  • Definition: Particles that are even smaller than an atom. The main types include:

  • Protons

    • Charge: Positively charged.

    • Location: Located in the nucleus.

  • Neutrons

    • Charge: Subatomic particle with no charge (neutral).

    • Location: Also located in the nucleus.

  • Electrons

    • Charge: Negatively charged.

    • Location: Located in electron shells around the nucleus.

• Nucleus

  • Description: A dense central core made of protons and neutrons. It accounts for most of an atom's mass.

• Atomic Number

  • Definition: The number of protons in the nucleus of an atom.

• Periodic Table

  • Definition: An arrangement of elements separated into groups based on a set of similar characteristics.

  • Chemical symbols: Each element is represented by a one or two-letter symbol (e.g. H for Hydrogen, He for Helium).

• Mass Number

  • Definition: The total number of protons and neutrons in an atom.

• Calculating Number of Neutrons

  • Formula: $ext{Number of Neutrons} = ext{Mass Number} - ext{Atomic Number}$

• Isotopes

  • Definition: Atoms of the same element that have the same number of protons but different amounts of neutrons.

Model of the Atom

• Protons

  • Location: In the nucleus.

  • Charge: Positively charged.

  • Relative Weight: 1.

• Neutrons

  • Location: In the nucleus.

  • Charge: No charge (neutral).

  • Relative Weight: 1.

• Electrons

  • Location: In electron shells.

  • Charge: Negatively charged.

  • Relative Weight: 0.

Questions and Observations

• Observation: The nucleus accounts for most of the atom's mass, while the electrons account for most of the atom's volume.

• Example Elements:

  • Fluorine:

  • Atomic Number: 9

  • Iodine:

  • Atomic Number: 53

  • # of Protons: 53

  • # of Electrons: 53

• Similarity Between Elements: Magnesium and Barium are similar because they are in the same group in the periodic table.

• Oxygen Isotopes:

  • Example: Oxygen-16 and Oxygen-17.

  • Similarities: Same atomic number; differences are due to neutrons which have no charge.

Isotopes Example

• Carbon Isotopes:

  • Carbon-12:

  • # of Protons: 6

  • # of Neutrons: 6

  • Carbon-13:

  • # of Protons: 6

  • # of Neutrons: 7

  • Carbon-14:

  • # of Protons: 6

  • # of Neutrons: 8

• Atomic Mass

  • Definition: The average atomic mass of all the isotopes of an element.

Element Grid and Review

1. Electron: Definition - A negatively charged subatomic particle.

2. Location of Protons: Found in the nucleus.

3. Neutral Particles: Neutrons have no charge.

4. Modern Model of the Atom:

   • Atoms consist of a nucleus surrounded by electrons.

5. Atomic Number:

   • Number of protons in the nucleus of an atom.

6. Uniqueness of Atomic Number: Every element has its own atomic number; no two elements share the same atomic number.

7. Element with Smallest Atomic Number: Hydrogen has atomic number 1.

8. Mass of Neutrons and Protons:

   • Their masses are similar, both are counted as 1 AMU (atomic mass unit).

9. Count of Electrons: The number of protons is equal to the number of electrons in a neutral atom.

10. Mass Measurement: The mass of an atom is primarily measured in AMUs, with electrons considered negligible in mass for this measurement.

11. Mass Number: Total number of protons and neutrons in an atom.

12. Data Table Exercise for Practice:

    • Calculate and fill in the atomic number, mass number, and count of protons, neutrons, and electrons for various elements such as Lithium, Fluorine, Magnesium, and Oxygen.

• Example Data:

  • Lithium:

  • Symbol: Li

  • Atomic Number: 3

  • Atomic Mass: 6.941

  • # of Protons: 3

  • # of Neutrons: 4

  • # of Electrons: 3

  • Fluorine:

  • Atomic Number: 19

These notes capture the essential elements of atomic structure, definitions, examples, and observations based on the provided transcript material.