Atoms and Atomic Structure Study Notes

Atoms and Atomic Structure

What Is Matter?

  • Definition of Matter:
    • Matter describes all of the physical substances around us.
    • The Universe is comprised of matter and energy.
    • Anything that has mass and takes up space (volume).
  • Examples of Matter:
    • A brick has mass and takes up space.
    • A desk has mass and takes up space.
    • A pencil has mass and takes up space.
    • Air has mass and takes up space.
  • Reflection Point:
    • All the examples mentioned are considered matter because they have mass and occupy space.
    • Question posed: Can you think of anything that would not be considered matter?

What Is an Atom?

  • Definition of an Atom:
    • The smallest unit of an element.
    • An atom consists of a central nucleus surrounded by one or more electrons.
    • Matter is made up of atoms.
    • An atom is described as the smallest whole particle of matter.
  • Subatomic Particles:
    • Subatomic particles are smaller than atoms and are the tiny components that make up an atom.

What Is the Nucleus?

  • Definition of Nucleus:
    • The nucleus is the central part of an atom.
    • Composed of protons and neutrons.
    • The nucleus contains most of an atom's mass.

What Is a Proton?

  • Definition of Proton:
    • Protons are positively charged particles that help constitute the nucleus of the atom.
  • Characteristics of Protons:
    • The number of protons is equal to the atomic number of the atom.
    • Protons contribute to the atomic mass.
    • In an uncharged atom, the number of protons is equal to the number of electrons.

What Is a Neutron?

  • Definition of Neutron:
    • Neutrons are neutral particles that possess no electric charge.
  • Characteristics of Neutrons:
    • They also help constitute the nucleus of the atom.
    • Neutrons contribute to the atomic mass.

What Is an Electron?

  • Definition of Electron:
    • Electrons are negatively charged particles found outside the nucleus of the atom.
  • Characteristics of Electrons:
    • They move rapidly around the nucleus, creating what is known as an electron cloud.
    • The mass of an electron is insignificant when compared to the mass of protons and neutrons.
    • In an uncharged atom, the number of electrons equals the number of protons.
    • Electrons are involved in the formation of chemical bonds.
  • Atomic Mass:
    • The atomic mass of an atom is the total mass of that atom.
    • It is approximately equal to the sum of protons and neutrons in the atomic nucleus; electrons have a negligible mass.
  • Atomic Number:
    • The atomic number is defined as the number of protons contained in the nucleus of an atom.
    • The atomic number determines the identity of an element and its position in the periodic table.

The End