Chemistry: Atoms, Elements and Particles

• A chemical symbol is used for representing an element.

Parts of an Atom

• The two main parts of an atom are the nucleus and the electron cloud.

Size and Mass

• The electron cloud (or the space the electrons occupy) is larger than the nucleus.
• The nucleus has a greater mass than the electron cloud.

Particles in an Atom

• Protons are found in the nucleus and have a positive charge.
• Neutrons are located in the nucleus and have no charge (neutral).
• Electrons are found orbiting the nucleus in electron shells and have a negative charge.

Atomic Number

• The atomic number of an element indicates the number of protons and the number of electrons in a neutral atom of that element.

Tevatron

• A Tevatron was a particle accelerator that accelerates particles to high speeds and collides them to study their components.

Quarks

• Quarks are fundamental particles that make up protons and neutrons.
• They are found inside protons and neutrons, within the nucleus of an atom.

Number of Quarks

• There are six types (or "flavors") of quarks.

Hard Quarks

• The top quark was hard to find due to its high mass.

Negligible Particles

• Electrons are so small that their mass is often not considered when determining the mass of an element.

Mass Number

• The mass number is equal to the number of protons plus the number of neutrons in an atom's nucleus.
• Mass number is used to determine the mass of an isotope.

Isotopes

• To find the most common isotope of an element, compare their natural abundance.
• Carbon-12 is the most common isotope of carbon.

Periodic Table

• Dmitri Mendeleev organized the periodic table.
• The periodic table is organized by increasing atomic number and recurring chemical properties.

Electron Movement

• Electrons move around the nucleus.

Electron Location

• Electrons are found in electron shells, also called energy levels or orbitals.

Electron Energy

• The amount of energy that electrons have is determined by the energy level or shell they occupy. Electrons in outer shells have higher energy.

Period Number

• The period number indicates the number of electron shells in an atom.

Vertical Columns

• Vertical columns in the periodic table are called groups or families.

Electron Shell Capacity

• The first electron shell can hold up to 2 electrons.
• The second electron shell can hold up to 8 electrons.

Element Chart

• Magnesium (Mg) has an atomic number of 12, is in Period 3, Group 2, has 12 protons and 12 electrons.
• Calcium (Ca) has an atomic number of 20, is in Period 4, Group 2, has 20 protons and 20 electrons.
• Helium (He) has an atomic number of 2, is in Period 1, Group 18, has 2 protons and 2 electrons.

Dot Diagrams

• Dot diagrams (Lewis dot structures) are used to represent valence electrons and how they bond.

New Elements

• New elements are made through nuclear reactions, such as in particle accelerators or in stars.

Understand the basics of atoms, including the nucleus and electron cloud. Learn about protons, neutrons, electrons, atomic numbers, Tevatrons, and quarks, and how they define elements in chemistry.